Publications
2024
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(2024) Cell Reports Physical Science. 5, 5, 101963. Abstract[All authors]
Cotton ovule in vitro cultures are a promising platform for exploring biofabrication of fibers with tailored properties. When the ovules' growth medium is supplemented with chemically synthesized cellulose precursors, it results in their integration into the developing fibers, thereby tailoring their end properties. Here, we report the feeding of synthetic glucosyl phosphate derivative, 6-deoxy-6-fluoro-glucose-1-phosphate (6F-Glc-1P) to cotton ovules growing in vitro, demonstrating the metabolic incorporation of 6F-Glc into the fibers with enhanced mechanical properties and moisture-retention capacity while emphasizing the role of molecular hierarchical architecture in defining functional characteristics and mechanical properties. This incorporation strategy bypasses the early steps of conventional metabolic pathways while broadening the range of functionalities that can be employed to customize fiber end properties. Our approach combines materials science, chemistry, and plant sciences to illustrate the innovation required to find alternative solutions for sustainable production of functional cotton fibers with enhanced and emergent properties.
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(2024) Macromolecular Materials and Engineering. 309, 3, 2300337. Abstract
Cellulose modification often employs chemical processes to tailor its properties and functionalities to fit the demands of a wide range of applications, maximizing its potential as a versatile and sustainable material. From both synthetic and environmental standpoints, one of the ultimate goals is to achieve significant modifications to enhance the end properties of the cellulose while minimizing the number of modified building blocks. The current study demonstrates that a synthetic glucose derivative, 6-deoxy-6-fluoro-glucose (6F-Glc), fed into the fertilized cotton ovules, resulted in the accumulation of fluorine inside the cotton fibers with no apparent alteration to their morphology or development. These fibers exhibited a degree of substitution of 0.006, which is 170 times lower than that reported for chemical methods for cellulose modification. However, the physical characterization of the modified fibers showed a surprisingly large impact of this low-level modification on the cellulose structure (e.g., hydrogen bonding network rearrangement) and a modest increase in the mechanical properties of the fibers. The obtained results exemplify the use of biological systems to introduce low quantities of new functionalities while maximizing the impact on fiber properties.
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(2024) ACS Applied Materials and Interfaces. 16, 5, p. 6327-6336 Abstract
The biomineralizing bacterium Sporosarcina pasteurii has attracted considerable interest in the area of geotechnical engineering due to its ability to induce extracellular mineralization. The presented study investigated S. pasteurii\u2019s potential to induce the mineralization of alkali-earth metal carbonate coatings on different polymeric 3D-printed flat surfaces fabricated by different additive manufacturing methods. The use of calcium, barium, strontium, or magnesium ions as the source resulted in the formation of vaterite (CaCO3), witherite (BaCO3), strontianite (SrCO3), and nesquehonite MgCO3·3H2O, respectively. These mineral coatings generally exhibit a compact, yet variable, thickness and are composed of agglomerated microparticles similar to those formed in solution. However, the mechanism behind this clustering remains unclear. The thermal properties of these biologically induced mineral coatings differ from their inorganic counterpart, highlighting the unique characteristics imparted by the biomineralization process. This work seeks to capitalize on the bacterium S. pasteurii\u2019s ability to form an alkali-earth metal carbonate coating to expand beyond its traditional use in geoengineering applications. It lays the ground for a novel integration of biologically induced mineralization of single or multilayered and multifunctional coating materials, for example, aerospace applications.
2023
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(2023) Frontiers in Plant Science. 14, 1242150. Abstract
Fluorescent glucose derivatives are valuable tools as glucose analogs in plant research to explore metabolic pathways, study enzyme activity, and investigate cellular processes related to glucose metabolism and sugar transport. They allow visualization and tracking of glucose uptake, its utilization, and distribution within plant cells and tissues. This study investigates the phenotypic and metabolic impact of the exogenously fed glucose derivative, 2-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-2-deoxyglucose) (2-NBDG) on the fibers of Gossypium hirsutum (Upland cotton) ovule in vitro cultures. The presence of 2-NBDG in the culture medium did not lead to macroscopic morphological alterations in ovule and fiber development or to the acquisition of fluorescence or yellow coloration. Confocal laser scanning microscope imaging and chromatographic analysis of cotton ovules\u2019 outer rim cross-sections showed that the 2-NBDG is transported from the extracellular space and accumulated inside some outer integument cells, epidermal cells, and fertilized epidermal cells (fibers), but is not incorporated into the cell walls. Untargeted metabolic profiling of the fibers revealed significant changes in the relative levels of metabolites involved in glycolysis and upregulation of alternative energy-related pathways. To provide biochemical and structural evidence for the observed downregulation of glycolysis pathways in the fibers containing 2-NBDG, kinetics analysis and docking simulations were performed on hexokinase from G. hirsutum (GhHxk). Notably, the catalytic activity of heterologously expressed recombinant active GhHxk exhibited a five-fold decrease in reaction rates compared to D-glucose. Furthermore, GhHxk exhibited a linear kinetic behavior in the presence of 2-NBDG instead of the Michaelis-Menten kinetics found for D-glucose. Docking simulations suggested that 2-NBDG interacts with a distinct binding site of GhHxk9, possibly inducing a conformational change. These results highlight the importance of considering fluorescent glucose derivatives as ready-to-use analogs for tracking glucose-related biological processes. However, a direct comparison between their mode of action and its extrapolation into biochemical considerations should go beyond microscopic inspection and include complementary analytical techniques.
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(2023) ChemBioChem. 24, 16, e202300388. Abstract
Glycosyltransferases (GTs) are a large and diverse group of enzymes responsible for catalyzing the formation of a glycosidic bond between a donor molecule, usually a monosaccharide, and a wide range of acceptor molecules, thus, playing critical roles in various essential biological processes. Chitin and cellulose synthases are two inverting processive integral membrane GTs, belonging to the type-2 family involved in the biosynthesis of chitin and cellulose, respectively. Herein, we report that bacterial cellulose and chitin synthases share an E-D-D-ED-QRW-TK active site common motif that is spatially co-localized. This motif is conserved among distant bacterial evolutionary species despite their low amino acid sequence and structural similarities between them. This theoretical framework offers a new perspective to the current view that bacterial cellulose and chitin synthases are substrate specific and that chitin and cellulose are organism specific. It lays the ground for future in vivo and in silico experimental assessment of cellulose synthase catalytic promiscuity against uridine diphosphate N-acetylglucosamine and chitin synthase against uridine diphosphate glucose, respectively.
2022
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(2022) Proceedings of the National Academy of Sciences. 119, 25, e212343911. Abstract
Pyrotechnology is a key element of hominin evolution. The identification of fire in early hominin sites relies primarily on an initial visual assessment of artifacts\u2019 physical alterations, resulting in potential underestimation of the prevalence of fire in the archaeological record. Here, we used a suite of spectroscopic techniques to counter the absence of visual signatures for fire and demonstrate the presence of burnt fauna and lithics at the Lower Paleolithic (LP) open-air site of Evron Quarry (Israel), dated between 1.0 and 0.8 Mya and roughly contemporaneous to Gesher Benot Ya\u2019aqov where early pyrotechnology has been documented. We propose reexamining finds from other LP sites lacking visual clues of pyrotechnology to yield a renewed perspective on the origin, evolution, and spatiotemporal dispersal of the relationship between early hominin behavior and fire use.
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(2022) Journal of Quaternary Science. 37, 4, p. 612-638 Abstract
The Middle Pleistocene archaeological record of the southern Levant has proven key to understanding human evolution and intercontinental faunal biogeography. Knowledge of archaeological sites of that period in the southern Levant is biased, with most Middle Pleistocene localities in the Mediterranean areas in the north, despite the mosaic of environments that mark the entire region. A key Middle Pleistocene location in the Judean Desert \u2013 on the eastern margin of the Mediterranean zone \u2013 is the site of Oumm Qatafa, excavated in the early 1900s, which yielded a faunal collection spanning an estimated time period of 500\u2013200\u2009kya. Here, we present a revised taxonomy of the macromammalian fauna from the site, discuss the palaeoenvironmental implications of this assemblage, and relate the finds to other Pleistocene sites from the Levant. These data enable a more precise palaeoenvironmental reconstruction which attests to an open landscape, but with the addition of a mesic Mediterranean component close by. In addition, detailed taphonomic observations on butchery marks and Fourier transform infrared spectroscopy analysis of burnt bone link the fauna for the first time to anthropogenic activities in the cave.
2021
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(2021) Chemical Geology. 582, 120427. Abstract
Eocene flint 48\u201356.0 million years old (mya) from the Negev desert (Israel) was characterized using a suite of analytical techniques. High-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) of the inorganic component showed the texture, morphology, size, and distribution of two silica polymorphs: α\u2013quartz and moganite. While euhedral forms were attributed to α-quartz, moganite crystals were comprised of spherulitic grains. An electron less-dense amorphous material (no scattering under SAED) was found between the siliceous crystallites. Energy dispersive X-rays (EDS) and electron energy loss spectroscopy (EELS) demonstrated that this electron less-dense amorphous material is composed solely of carbon. Low vacuum, low energy backscattered environmental scanning electron microscopy (BSE-eSEM) imaging of flint surfaces showed the presence of micrometer-sized organic inclusions randomly distributed throughout the siliceous matrix. Energy-dispersive X-ray studies (EDS) demonstrated that these organic micro-inclusions were composed of carbon, sulfur, and nitrogen with a C/N ratio attributed to marine sources. These micro-inclusions were not directly associated with hard-shell fossils. BSE-eSEM imaging conditions allowed the identification of entrapped carbon-rich organic material, which is not possible when applying commonly used electron microscopy conditions that require carbon coating and high acceleration voltages, rendering carbon-rich features electron-transparent. Phase contrast-enhanced micro-computed tomography (PC-μCT) showed that these organic micro-inclusions were randomly distributed throughout the siliceous matrix.Time-of-flight secondary ion mass spectrometry (ToF-SIMS), nano-Fourier transform infrared spectroscopy (nano-FTIR), and scanning probe microscopy (SPM) were used to further characterize these organic micro-inclusions. These three in situ analytical techniques with nanometer resolution provided complementary information on the chemical composition and structure of the organic material. Specifically, ToF-SIMS analysis revealed amino acid and hydrocarbon mass spectra fingerprints inside the organic micro-inclusions. While the former were exclusively found in the organic micro-inclusions, the mass spectral fingerprints for hydrocarbons were also found in the siliceous matrix in agreement with the HR-TEM/EDS/EELS results, where pure carbon was found between the siliceous nanocrystals. While ToF-SIMS provides chemical information, it does not provide structural information. Nano-FTIR analysis showed the presence of amide I and II infrared vibrations exclusively on the organic micro-inclusions. The scanning probe microscopy (SPM) techniques Peak Force Quantitative Nanomechanics (PF-QNM) and Contact Resonance Atomic Force Microscopy (CR-AFM) were used to assess the mechanical properties. PF-QNM measurements on the organic micro-inclusions, under dry and liquid conditions, demonstrated that the organic micro-inclusions swell upon hydration and soften, pointing toward the presence of hydrophilic molecules in agreement with nano-FTIR and ToF-SIMS results. CR-AFM allows in situ determination of the mechanical properties of materials with high stiffness at nanometer resolution. This technique, rarely used in a geological context, revealed that the organic micro-inclusions had an unusually high stiffness atypical for modern organic material, which was attributed to molecular cross-linking promoted by diagenesis.This work provided a comprehensive view of the inorganic and organic components of Eocene flint from the Negev desert with implications for paleontology and archaeology. It offers a roadmap of novel complementary techniques that can be used in the exploration of entrapped organic material in flint.
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(2021) Humanities & Social Sciences Communications. 8, 295. Abstract
Deep learning is a powerful tool for exploring large datasets and discovering new patterns. This work presents an account of a metric learning-based deep convolutional neural network (CNN) applied to an archaeological dataset. The proposed account speaks of three stages: training, testing/validating, and community detection. Several thousand artefact images, ranging from the Lower Palaeolithic period (1.4 million years ago) to the Late Islamic period (fourteenth century AD), were used to train the model (i.e., the CNN), to discern artefacts by site and period. After training, it attained a comparable accuracy to archaeologists in various periods. In order to test the model, it was called to identify new query images according to similarities with known (training) images. Validation blinding experiments showed that while archaeologists performed as well as the model within their field of expertise, they fell behind concerning other periods. Lastly, a community detection algorithm based on the confusion matrix data was used to discern affiliations across sites. A case-study on Levantine Natufian artefacts demonstrated the algorithm\u2019s capacity to discern meaningful connections. As such, the model has the potential to reveal yet unknown patterns in archaeological data.
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(2021) Journal of Structural Biology. 213, 1, 107665. Abstract
Biomineralization is a common strategy adopted by organisms to support their body structure. Plants practice significant silicon and calcium based biomineralization in which silicon is deposited as silica in cell walls and intracellularly in various cell-types, while calcium is deposited mostly as calcium oxalate in vacuoles of specialized cells. In this review, we compare cellular processes leading to protein-dependent mineralization in plants, diatoms and sponges (phylum Porifera). The mechanisms of biomineralization in these organisms are inherently different. The composite silica structure in diatoms forms inside the cytoplasm in a membrane bound vesicle, which after maturation is exocytosed to the cell surface. In sponges, separate vesicles with the mineral precursor (silicic acid), an inorganic template, and organic molecules, fuse together and are extruded out. In plants, calcium oxalate precursors are concentrated in a vacuolar vesicle containing a protein matrix which is never exocytosed. Silica deposition in grass silica cells takes place outside the cell membrane when the cells secrete the mineralizing protein into the apoplasm rich with silicic acid (the mineral precursor molecules). Our review infers that the organism complexity and precursor reactivity (calcium and oxalate versus silicic acid) are main driving forces for the evolution of varied mineralization mechanisms.
2020
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(2020) Paléorient. 46, 1-2, p. 43-68 Abstract[All authors]
This paper presents findings from the first season of excavations conducted at the mountain-top site of Naḥal Roded 110, located in the southern Negev desert near Eilat, Israel. Both radiocarbon and optically stimulated luminescence date the site to the Late Pre-Pottery Neolithic B (LPPNB, late 8th millennium BC). Palaeoenvironmental data from pollen and charcoal indicate that arid conditions prevailed in the region, with a strong Saharo-Arabian influence. The finds—flints, marine shells and stone objects show affinities to LPPNB settlement sites in the region, while the faunal assemblage is unique and comprised solely of raptors. These features raise the question as to the function of the site—a specialised hunting camp, ritual site or our preferred explanation, a combination of the two.
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(2020) ACS Omega. 5, 50, p. 32490-32497 Abstract
Global warming has prompted a search for new materials that capture and sink carbon dioxide (CO2). Biochar is a derivative of biomass pyrolysis and a carbon sink mainly used to improve crop production. This work explores the underlying mechanism behind biochar\u2019s electric conductivity using a wide range of feedstocks and its combination with a binder (gypsum). This gypsum\u2013biochar composite exhibits decreased density and flexural moduli with increasing biochar content, particularly after 20% w/w. Gypsum\u2013biochar drywall-like composite prototypes display increasing shielding efficiency mostly in the microwave range as a function of biochar content, differing from other conventional metal (copper) and synthetic carbon-based materials. This narrow range of electromagnetic interference (EMI) shielding is attributed to natural alignment (isotropy) of the carbon ultrastructure (e.g., lignin) induced by heat and intrinsic interconnectivity in addition to traditional phenomena such as dissipation of surface currents and polarization in the electric field. These biomass-derived products could be used as sustainable lightweight materials in a future bio-based economy.
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(2020) Israel Journal of Chemistry. 12, p. 1197-1207 60. Abstract
Semi-synthetic biological fabrication explores biological systems and their biosynthetic pathways as inspiration for designing precursor analogs that can be metabolized in a similar manner as the natural substrates by organisms to yield new materials with tailored properties. Here we report the biological incorporation of a metabolizing iodinated glucose analog (2-Deoxy-2-iodo-D-glucose, DIG) into Gossypium hirsutum cotton fibers in an ovule in-vitro model. Structural modifications occur at the level of crystallite arrangement and compaction, with amorphization of the fibers and alteration of the H-bond network between the cellulose nanofibrils. We further show that DIG can serve as a non-radioactive micro computed tomography contrast agent (μCT). The fibers act as glucose sinks that accumulate DIG, enabling its detection by μCT. Quantitative analysis shows that the fibers are more oriented when incubated with DIG. This work demonstrates the advantages of using higher organisms for biological in-situ transformation of economically important raw materials over conventional chemical surface modification processes, thereby providing a scientific foundation for implementing future alternatives and sustainable manufacturing strategies towards a bio-based economy.
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(2020) Nature Human Behaviour. 4, 10, p. 221-+ Abstract
Production of stone artefacts using pyro-technology is known from the Middle and Upper Palaeolithic of Europe and the Levant, and the Middle Stone Age in Africa. However, determination of temperatures to which flint artefacts were exposed is impeded by the chemical and structural variability of flint. Here we combine Raman spectroscopy and machine learning to build temperature-estimation models to infer the degree of pyro-technological control effected by inhabitants of the late Lower Palaeolithic (Acheulo-Yabrudian) site of Qesem Cave, Israel. Temperature estimation shows that blades were heated at lower median temperatures (259 °C) compared to flakes (413 °C), whereas heat-induced structural flint damage (for example, pot-lids and microcracks) appears at 447 °C. These results are consistent with a differential behaviour for selective tool production that can be viewed as part of a plethora of innovative and adaptive behaviours of Levantine hominins >300,000 years ago.
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(2020) Journal of Archaeological Science: Reports. 31, 102263. Abstract
Pottery kilns are usually recognizable in the archaeological record based on their prominent and characteristic architectural features, evidence of exposure to high temperatures and associated waste products. Here we describe how we identified a kiln that has no readily recognizable architectural features, but does have an upper chamber full of broken pottery, and a lower chamber full of ash. The typology of the pottery in the upper chamber and radiocarbon dating show that the kiln was constructed after around 600 CE and was used until the early 7th century. The confining structures around these two chambers are sediments, some of which were deliberately brought to the site. A detailed study of the section through the kiln using on-site and off-site microarchaeological techniques revealed much about the firing conditions. The ash is composed almost entirely of phytoliths with a small amount of calcite. Surprisingly the diversity of phytolith morphotypes identified was low, and many of the phytoliths are unusually large multicells. The phytolith analysis shows that the fuel was mainly the stalks/chaff of domesticated grasses, most probably wheat, and probably not animal dung. Many of the phytolith morphologies are distorted and charred due to exposure to high temperatures, and show birefringence. Infrared spectra show that the phytoliths have partially recrystallized into the high temperature silicate mineral cristobalite. Slags formed close to the inner surfaces of the confining sediments presumably from melted phytoliths, and some of the clay-rich sediment close to these surfaces is clearly heat altered. These observations show that the temperatures in the firing chamber ranged from around 700 to 900 °C. The calcite in this ash is extremely disordered at the atomic level, based on the grinding curve analysis. A partial reconstruction of the kiln structure shows that the pottery chamber is above the firing chamber, and there is no constructed partition that separates the two chambers. The identification and characterization of this unusual kiln depended significantly on the use of the microarchaeological approach.
2019
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(2019) Small. 15, 50, 1906277. Abstract[All authors]
In the originally published article, the reference list of the Supporting Information was incorrect, and the composition of the medium used in bacterial γ‐polyglutamate (PGA) production was incomplete. The updated Supporting Information file is included with this correction. The authors apologize for any misunderstanding this may have caused.
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(2019) Journal of Micromechanics and Microengineering. 29, 10, 105009. Abstract
Micro/nano thermogravimetry (TG) employing MEMS has significant potential to improve the minimum sample mass and mass resolution as compared to commercial TG instruments. Although there have been a few previous reports on MEMS TG, none of them have critically analysed the obtained TG curve in detail. In this work, we have designed and fabricated a microelectromechanical thermogravimetric device (MMTG) with integrated microheaters and temperature sensors. The mass sensitivity of the device was estimated to be 0.89 pg Hz(-1) which outperforms the standard TG approaches. We tested the MMTG performance with CuSO4 center dot 5H(2)O crystals. The final mass loss ratio corresponds to the theoretically expected value, although the obtained TG curve deviated from the standard TG curve of CuSO4 center dot 5H(2)O obtained from commercial TG instruments. We attributed the deviation to the inherent temperature non-uniformity, non-isothermal conditions and temperature gradients of metallic-wire based microheaters. Finite element (FE) simulations were carried out in order to confirm and gain insights into the non-uniform heating phenomena of microheater and sample. Based on the simulation results, we propose designs that can be realized to make MEMS TG a successful enterprise.
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(2019) Materials Science & Engineering: C-Materials For Biological Applications. 100, p. 315-322 Abstract
Herein appropriateness of nonfunctionalized mesoporous silica nanoparticles SBA-15 and functionalized with (3-chloropropyl)triethoxysilane (-> SBA-15 similar to Cl) and (3-aminopropyl)triethoxysilane (-> SBA-15 similar to NH2) on delivery of physically adsorbed Ph3Sn(CH2)(6)OH (Sn6) is evaluated. Fluorescent nanomaterial, bearing isatoic moiety, loaded with Sn6 (-> SBA center dot 15 similar to NF vertical bar Sn6) was used for cellular uptake study. The fluorescent nanomaterial is efficiently acquired and distributed into the cytoplasm of the cells even after 2 h of cultivation. According to the attained data, all SBA-15 materials loaded with Sn6 diminished cellular viability in dose dependent manner while carriers alone (SBA-15, SBA-15 similar to Cl, SBA-15 similar to NH2) did not show cytotoxicity against B16 cells. According to the MC50 values structural modification of SBA-15 did not improve the efficacy of tested drug. While progressive apoptosis was detected upon the treatment with SBA similar to 15 vertical bar Sn6, exposure of cells to SBA similar to 15 vertical bar Sn6 revealed extinguished apoptosis in time, accompanied with lower caspase activity. This effect is probably due to triggered autophagic process under the treatment with the SBA similar to 15 vertical bar Sn6, thus opposed to apoptosis. Presented results suggested that functionalization of SBA-15 was not beneficial for the efficacy of loaded drug, thus, all of them are almost equally efficient considering loaded Sn6 content. Importantly, functionalization of SBA-15 does have an influence on the mode of action and differentiation inducing properties.
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(2019) Small. 15, 22, 1805312. Abstract
The impressive mechanical properties of natural composites, such as nacre, arise from their multiscale hierarchical structures, which span from nano- to macroscale and lead to effective energy dissipation. While some synthetic bioinspired materials have achieved the toughness of natural nacre, current production methods are complex and typically involve toxic chemicals, extreme temperatures, and/or high pressures. Here, the exclusive use of bacteria to produce nacre-inspired layered calcium carbonate-polyglutamate composite materials that reach and exceed the toughness of natural nacre, while additionally exhibiting high extensibility and maintaining high stiffness, is introduced. The extensive diversity of bacterial metabolic abilities and the possibility of genetic engineering allows for the creation of a library of bacterially produced, cost-effective, and eco-friendly composite materials.
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(2019) Antiquity. 93, 367, p. e4 4. Abstract
Excavations at the Pre-Pottery Neolithic B ritual site of Naḥal Roded 110 in the Southern Negev, Israel, have revealed evidence—unique to this region—for on-site flint knapping and abundant raptor remains.
[All authors]
2018
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(2018) Fibers. 6, 1, 11. Abstract
Cotton is the leading fiber source in the textile industry and one of the world's most important crops. Despite its economic interest, cotton culture exerts an enormous pressure on natural resources (land and water) and has a negative impact on the environment (abuse of pesticides). Thus, alternative cotton growing methods are urged to be implemented. Recently, we have demonstrated that Gossypium hirsutum ("Upland" cotton) can be grown in a greenhouse (controlled conditions) and hydroponically. Here we report on the elucidation of the structural changes of the Gossypium hirsutum fibers during maturation grown [10, 14, 17, 20, 36 and 51 days post anthesis (dpa)] under a greenhouse and hydroponically, by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy with attenuated total reflectance (FT-IR ATR) and thermal gravimetric analysis/differential scanning calorimetry (TGA/DSC). The transition from primary to secondary cell wall growth occurs between 17 and 20 dpa-similarly to the soil-based cultures. However, this new cotton culture offers an advantageous pesticide and soil-free all year-round closed system with efficient water use yielding standardized mature fibers with improved properties (maturity, strength, length, whiteness).
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(2018) ACS Applied Nano Materials. 1, 3, p. 1050-1057 Abstract
Multicomponent nanostructures containing purely organic or inorganic as well as hybrid organic–inorganic components connected through a solid interface are, unlike conventional spherical particles, able to combine different or even incompatible properties within a single entity. They are multifunctional and resemble molecular amphiphiles, like surfactants or block copolymers, which makes them attractive for the self-assembly of complex structures, drug delivery, bioimaging, or catalysis. We have synthesized Pd@FexO heterodimer nanoparticles (NPs) to fabricate a macroporous, hydrophobic, magnetically active, three-dimensional (3D), and template-free hybrid foam capable of repeatedly separating oil contaminants from water. The Pd domains in the Pd@FexO heterodimers act as nanocatalysts for the hydrosilylation of polyhydrosiloxane and tetravinylsilane, while the FexO component confers magnetic properties to the final functional material. Pd@FexO heterodimers were synthesized by heterogeneous nucleation and growth of the iron oxide domain onto presynthesized Pd NPs at high temperatures in solution. The morphology, structure, and magnetic properties of the as-synthesized heterodimers were characterized by transmission electron microscopy (TEM), X-ray diffraction, Mössbauer spectroscopy, and a superconducting quantum interference device. The epitaxial growth of the FexO domain onto Pd was confirmed by high-resolution TEM. A potential application of the 3D hydrophobic magnetic foam was exploited by demonstrating its ability to soak oil beneath a water layer, envisioning its use in oil sampling during oil prospection drilling, or to remove oil films after oil spills.
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(2018) Small Methods. 3, 1, 1800136. Abstract
What is biological fabrication? It is combining the ability of designing bioinspired molecules (chemistry) with nature's complexity and ingenious paths (biology) in order to produce new composite materials with emergent properties while being able to tailor the said materials' end-functionality or functionalities. And what is material farming? It is the possibility to implement alternative and sustainable methodologies of biological fabrication toward larger scales, real-life applications, and marketable products. The proof-of-principle is recently demonstrated for biological fabrication of fibers with tailored properties using an in vitro cotton culture and designed glucose derivatives yielding fluorescent and supermagnetic cotton fibers. This new "fabrication approach" will allow, in the future, to sustainably transform abundant raw materials into an innovative new class of composite functional materials, such as a new generation of smart textiles in the above case of cotton. This essay provides a very brief overview of the research done in cotton, the methodology used for the biological fabrication of cotton fibers with tailored properties and, finally, showcases perspectives on the future of this new and exciting research field that challenges the present fabrication methodologies that heavily rely on an old mindset toward bio-based fabrication strategies.
2017
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(2017) Science. 357, 6356, p. 1118-1122 Abstract
Cotton is a promising basis for wearable smart textiles. Current approaches that rely on fiber coatings suffer from function loss during wear. We present an approach that allows biological incorporation of exogenous molecules into cotton fibers to tailor the material\u2019s functionality. In vitro model cultures of upland cotton (Gossypium hirsutum) are incubated with 6-carboxyfluorescein\u2013glucose and dysprosium\u20131,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid\u2013glucose, where the glucose moiety acts as a carrier capable of traveling from the vascular connection to the outermost cell layer of the ovule epidermis, becoming incorporated into the cellulose fibers. This yields fibers with unnatural properties such as fluorescence or magnetism. Combining biological systems with the appropriate molecular design offers numerous possibilities to grow functional composite materials and implements a material-farming concept.
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(2017) Journal of Structural Biology. 198, 3, p. 186-195 Abstract
The skeletal system of Demospongiae consists of siliceous spicules, which are composed of an axial channel containing an organic axial filament (AF) surrounded by a compact layer of hydrated amorphous silica. Here we report the ultrastructural investigations of the AF of siliceous spicules from two Demospongiae: Suberites domuncula and Tethya aurantium. Electron microscopy, electron diffraction and elemental mapping analyses on both longitudinal and transversal cross-sections yield that spicules's AF consist of a three-dimensional crystal lattice of six-fold symmetry. Its structure, which is the result of a biological growth process, is a crystalline assembly characterized by a lattice of organic cages (periodicity in the range of 6 nm) filled with enzymatically-produced silica. In general, the six-fold lattice symmetry is reflected by the morphology of the AF, which is characterized by six-fold facets. This seems to be the result of a lattice energy minimization process similar to the situation found during the growth of inorganic crystals. Our structural exploitation of three-dimensional organic lattices generated by biological systems is expected to contribute for explaining the relation between axial filament's ultrastructure and spicule's ultimate morphology. (C) 2017 Elsevier Inc. All rights reserved.
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(2017) Sensors. 17, 6, 1191. Abstract
In this paper, we apply a digital holographic microscope (DHM) in conjunction with stroboscopic acquisition synchronization. Here, the temperature-dependent decrease of the first resonance frequency (S-1(T)) and Young's elastic modulus (E-1(T)) of silicon micromechanical cantilever sensors (MCSs) are measured. To perform these measurements, the MCSs are uniformly heated from T-0 = 298 K to T = 450 K while being externally actuated with a piezo-actuator in a certain frequency range close to their first resonance frequencies. At each temperature, the DHM records the time-sequence of the 3D topographies for the given frequency range. Such holographic data allow for the extracting of the out-of-plane vibrations at any relevant area of the MCSs. Next, the Bode and Nyquist diagrams are used to determine the resonant frequencies with a precision of 0.1 Hz. Our results show that the decrease of resonance frequency is a direct consequence of the reduction of the silicon elastic modulus upon heating. The measured temperature dependence of the Young's modulus is in very good accordance with the previously-reported values, validating the reliability and applicability of this method for micromechanical sensing applications.
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(2017) Chemistry-A European Journal. 23, 21, p. 4973-4980 Abstract
Boron's unusual properties inspired major advances in chemistry. In nature, the existence and importance of boron has been fairly explored (e.g. bacterial signaling, plant development) but its role as biological catalyst was never reported. Here, we show that boric acid [B(OH)(3)] can restore chloroperoxidase activity of Curvularia inaequalis recombinant apo-haloperoxidase's (HPO) in the presence of hydrogen peroxide and chloride ions. Molecular modeling and semi-empirical PM7 calculations support a thermodynamically highly favored (bio)catalytic mechanism similarly to vanadium haloperoxidases (V-HPO) in which [B(OH)(3)] is assumedly located in apo-HPO's active site and a monoperoxyborate [B(OH)(3)(OOH)(-)] intermediate is formed and stabilized by interaction with specific active site amino acids leading ultimately to the formation of HOCl. Thus, B(OH)(3)-HPO provides the first evidence towards the future exploitation of borons role in biological systems.
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Microbially Induced Calcium Carbonate: Multilayer/Multimaterial Coatings on Non-conductive Materials(2017) Cultivated Building Materials. Basel, Switzerland: . p. 148-155 Abstract
Biominerals are minerals formed by organisms. The most prominent examples of such biominerals are bone, nacre, corals, sponge spicules, and shells of diatoms and radiolarian. Biomineral formation – so-called biomineralization – belongs to one of the most complex and yet fascinating processes driven by living organisms and is the end-product of a well-orchestrated coordination between inorganic and organic materials, driven by specialized cells and following a brick-mortar assembly principle. Since their discovery, biominerals have inspired several generations of scientists, engineers, architects, and designers. [first paragraph]
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(2017) Biocatalysis and Nanotechnology. p. 531-560 Abstract
The ambitious goal of biomimetic chemistry to mimic the structural and functional aspects of natural enzymes is at the center of interest by contemporary scientists. In the past decades, intensive efforts have been made to synthesize inorganic nanomaterials capable of mimicking natural enzymes termed as “artificial enzymes,” that are more stable and cost efficient compared to their natural counterpart (Wei and Wang, 2013; Breslow, 2006; Breslow and Overman, 1970). Based on previous studies of catalytically active model compounds, including metal complexes (Kirby and Hollfelder, 2009), 532polymers (Kirkorian et al., 2012; Klotz, 1984; Kofoed and Reymond, 2005; Wang et al., 2014; Wulff, 2001), supramolecules (Dong et al., 2011; Raynal et al., 2014) and biomolecules (Aiba et al., 2011; Breaker and Joyce, 1994; Mader and Bartlett, 1997; Pollack et al., 1986; Tramontano et al., 1986), new materials have been identified to imitate the biological functions of natural enzymes. Still, mimicking enzymatic reactions inside living organisms-especially in the presence of other competing reactions-remains a great challenge. Recently, several biocompatible inorganic nanomaterials were found to exhibit enzyme-like activities. Therefore, applications inside living cells or organisms could be possible in the future (Fan et al., 2012; Kim et al., 2012; Ragg et al., 2014). However, it is still an open question whether and in which form inorganic nanoparticles (NPs) can mimic the high efficiency and exceptional specificity of their natural counterparts (André et al., 2013). At the same time, enzyme-catalyzed reactions are greatly dependent on specific reaction conditions like temperature, pH or chemical structure of the substrates. For example, enzymes generally suffer from low stability in body fluids or organic solvents, short shelf life and high production costs. In contrast, inorganic NPs provide significant advantages compared to their natural counterpart, e.g., cost-efficient synthesis up to industrial scale and tolerance of major changes in reaction conditions, like temperature, pH or solvent. Additionally, NPs constitute the essential feature of enhanced chemical activity due to their large surface area leading to an increase in catalytic activity. Furthermore, the surface of NPs can be modified by post-synthetic steps. Suitable stabilizing ligands are based on chelating agents that bind tightly to the NP surface, which makes them versatile tools in various applications. Due to the functionalization process, NPs offer the possibility of specific cellular targeting in combination with drug delivery, enhancement of the solubility in different media or increase of their physiological compatibility as well as active site-substrate interactions (Breslow and Overman, 1970; André et al., 2013; D’Souza et al., 1987). Recently, great efforts have been made in identifying new materials with enzyme-like properties that are equally or even more efficient than their natural counterparts. An exceeding number of peroxidase mimics are among the reported materials, whereas 533only a few other enzymatic systems (e.g., superoxide dismutases, catalases, oxidases, haloperoxidases) have been explored so far.
2016
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(2016) Advanced Optical Materials. 4, 10, p. 1608-1613 Abstract
The complex process of supercontinuum generation (SG) is known to be exploitable for designing spatially coherent white light sources emitting light simultaneously in the ultraviolet, visible, and infrared ranges. Herein the first natural material able to generate in laboratory conditions a supercontinuum similar to those known from man-made photonic crystal fibers is described. The ability resides in siliceous 20-50 cm long spicules of the glass sponge Sericolophus hawaiicus. By shedding into the spicules optical peak intensities ranging from 1 to 100 TW cm(-2) the generation of a SG is revealed. The SG involves wavelengths between 650 and 900 nm and shows a maximum spectral spread for excitation at a wavelength of 750 nm. It is hypothesized that the SG is favored by spicules being a biocomposite that incorporates together isotopically pure biogenic silica (delta(30) Si = -3.28) and 15.2 +/- 1.3 mu g N -acetyl-glucosamine (chitin) per mg of silica. The internal organization of these spicules is distinguished by a solid silica core with a 1 mu m wide axial channel as well as a highly ordered silica-chitin composite. Such a composition and organization pattern may be of potential interest for the design of low temperature synthesis of future materials for light guidance.
[All authors] -
(2016) Journal of Structural Biology. 194, 3, p. 292-302 Abstract
Cotton is the one of the world's most important crops. Like any other crop, cotton growth/development and fiber quality is highly dependent on environmental factors. Increasing global weather instability has been negatively impacting its economy. Cotton is a crop that exerts an intensive pressure over natural resources (land and water) and demands an overuse of pesticides. Thus, the search for alternative cotton culture methods that are pesticide-free (biocotton) and enable customized standard fiber quality should be encouraged. Here we describe a culture of Gossypium hirsutum ("Upland" Cotton) utilizing a greenhouse and hydroponics in which the fibers are morphological similar to conventional cultures and structurally fit into the classical two-phase cellulose I model with 4.19 nm crystalline domains surrounded by amorphous regions. These fibers exhibit a single crystalline form of cellulose I-I-beta, monoclinic unit cell. Fiber quality bulk analysis shows an improved length, strength, whiteness when compared with soil based cultures. Finally, we show that our fibers can be spun, used for production of non-woven fabrics and indigo-vat stained demonstrating its potential in industrial and commercial applications. (C) 2016 Elsevier Inc. All rights reserved.
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(2016) Nanoscale. 8, 18, p. 9548-9555 Abstract
One endeavour of nanochemistry is the bottom-up synthesis of functional mesoscale structures from basic building blocks. We report a one-pot wet chemical synthesis of Ni@gamma-Fe2O3 superparticles containing Ni cores densely covered with highly oriented gamma-Fe2O3 (maghemite) nanorods (NRs) by controlled reduction/decomposition of nickel acetate (Ni(ac)(2)) and Fe(CO)(5). Automated diffraction tomography (ADT) of the Ni-Fe2O3 interface in combination with Mossbauer spectroscopy showed that selective and oriented growth of the gamma-Fe2O3 nanorods on the Ni core is facilitated through the formation of a Fe0.05Ni0.95 alloy and the appearance of superstructure features that may reduce strain at the Ni-Fe2O3 interface. The common orientation of the maghemite nanorods on the Ni core of the superparticles leads to a greatly enhanced magnetization. After functionalization with a catechol-functional polyethylene glycol (C-PEG) ligand the Ni@gamma-Fe2O3 superparticles were dispersible in water.
[All authors] -
(2016) Journal of Materials Chemistry B. 4, 46, p. 7423-7428 Abstract[All authors]
Superoxide radicals are associated with the development of many severe diseases, such as cancer. Under nonpathogenic conditions, the natural enzyme superoxide dismutase (SOD) regulates the intracellular superoxide concentrations, but nearly all tumor tissues show reduced SOD levels. Selective imaging in early progression stages remains a key requirement for efficient cancer diagnosis and treatment. Magnetic resonance imaging (MRI) as a noninvasive tool with high spatial resolution may offer advantages here, but MRI contrast agents exhibiting a redox-triggered change in the image contrast towards superoxide radicals have not been reported so far. Here we show that manganese oxide (MnO) nanoparticles (NPs) exhibit an intrinsic SOD-like activity, which is higher than that of the native Mn-dependent SOD. In addition, MnO NPs significantly enhance the MRI contrast when exposed to superoxide radicals, making them responsive MRI contrast agents for the treatment and imaging of cancer cells with reduced SOD levels.
2015
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(2015) Scientific Reports. 5, 13303. Abstract
Pottery was a traditional art and technology form in pre-colonial Amazonian civilizations, widely used for cultural expression objects, utensils and as cooking vessels. Abundance and workability of clay made it an excellent choice. However, inferior mechanical properties constrained their functionality and durability. The inclusion of reinforcement particles is a possible route to improve its resistance to mechanical and thermal damage. The Amazonian civilizations incorporated freshwater tree sponge spicules (cauixi) into the clay presumably to prevent shrinkage and crack propagation during drying, firing and cooking. Here we show that isolated siliceous spicules are almost defect-free glass fibres with exceptional mechanical stability. After firing, the spicule Young's modulus increases (from 28 +/- 5 GPa to 46 +/- 8 GPa) inferring a toughness increment. Laboratory-fabricated ceramic models containing different inclusions (sand, glass-fibres, sponge spicules) show that mutually-oriented siliceous spicule inclusions prevent shrinkage and crack propagation leading to high stiffness clays (E = 836 +/- 3 MPa). Pre-colonial amazonian potters were the first civilization known to employ biological materials to generate composite materials with enhanced fracture resistance and high stiffness in the history of mankind.
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(2015) Journal of Materials Chemistry B. 3, 11, p. 2371-2377 Abstract
Surface functionalized ZrO2 nanoparticles show strong photoluminescence and are a versatile tool for cellular targeting due to their chemical functionality. They are highly photostable, biocompatible and amenable to coupling with bioligands (e.g. secondary goat anti-rabbit antibody (GAR) and tri-phenyl phosphine (TPP)) via carbodiimide chemistry. Antibody (GAR) functionalized ZrO2 nanoparticles were used to image the nuclear protein Sirt6, whereas triphenyl phosphonium ion (TPP) functionalized ZrO2 nanoparticles specifically targeted the mitochondria. The versatility and easiness of the ZrO2 surface modification opens up new possibilities for designing non-toxic water dispersible and photostable photoluminescent NPs.
2014
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(2014) Marine Drugs. 12, 8, p. 4659-4676 Abstract
Iron, as inorganic ion or as oxide, is widely used by biological systems in a myriad of biological functions (e. g., enzymatic, gene activation and/or regulation). In particular, marine organisms containing silica structures-diatoms and sponges-grow preferentially in the presence of iron. Using primary sponge cell culture from S. domuncula-primmorphs-as an in vitro model to study the Demospongiae spiculogenesis, we found the presence of agglomerates 50 nm in diameter exclusively inside sponge specialized cells called sclerocytes. A clear phase/material separation is observed between the agglomerates and the initial stages of intracellular spicule formation. STEM-HRTEM-EDX analysis of the agglomerates (30-100 nm) showed that they are composed of pseudohexagonal nanoparticles between 5 and 15 nm in size, displaying lattice parameters corresponding to hematite (Fe2O3) and mixed iron oxide phases typically attributed to ferritin. Further analysis, using western blotting, inductively coupled plasma mass spectrometry (ICP-MS), sequence alignment analysis, immunostaining and magnetic resonance imaging (MRI), of mature spicule filaments confirm the presence of ferritin within these organic structures. We suggest that S. domuncula can be classified as a dual biomineralizating organism, i.e., within the same cellular structure two distinct biomineralizing processes can occur as a result of the same cellular/metabolic function, spiculogenesis.
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(2014) ACS Nano. 8, 5, p. 5182-5189 Abstract
Sulfite oxidase is a mitochondria-located molybdenum-containing enzyme catalyzing the oxidation of sulfite to sulfate in the amino acid and lipid metabolism. Therefore, it plays a major role in detoxification processes, where defects in the enzyme cause a severe infant disease leading to early death with no efficient or cost-effective therapy in sight. Here we report that molybdenum trioxide (MoO3) nanoparticles display an intrinsic biomimetic sulfite oxidase activity under physiological conditions, and, functionalized with a customized bifunctional ligand containing dopamine as anchor group and triphenylphosphonium ion as targeting agent, they selectively target the mitochondria while being highly dispersible in aqueous solutions. Chemically induced sulfite oxidase knockdown cells treated with MoO3 nanoparticles recovered their sulfite oxidase activity in vitro, which makes MoO3 nanoparticles a potential therapeutic for sulfite oxidase deficiency and opens new avenues for cost-effective therapies for gene-induced deficiencies.
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(2014) New Journal of Chemistry. 38, 5, p. 2031-2036 Abstract
Au-MnO heteroparticles were immobilized on the surface of TiO2 nanowires and tagged subsequently with a fluorescent ligand. The immobilization of the Au@MnO heteroparticles was achieved by functionalizing the TiO2 nanowire support with a polymer containing catechol anchor groups for binding to the metal oxide surface and amine groups for conjugation to the Au domains of the Au@MnO heteroparticles. The Au domain of the resulting TiO2@Au-MnO nanocomposite could be functionalized selectively with a thiol-tagged 24 mer oligomer containing Texas red (SH-ODN-TXS red), whereas a green dye (NBD-Cl) could be anchored selectively to the TiO2 "support'' using the free amine groups of the polymeric ligand. The binding of the NBD and the Texas red fluorophors was monitored by confocal microscopy and the functionalization of the metal oxide nanoparticles was monitored by UV-Vis spectroscopy. All composite products were characterized by transmission electron microscopy (TEM) combined with energy dispersive X-ray spectroscopy (EDX), confocal laser scanning microscopy (CLSM) and UV-Vis spectroscopy.
2013
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(2013) Science. 339, 6125, p. 1298-1302 Abstract
Silicatein-alpha is responsible for the biomineralization of silicates in sponges. We used silicatein-alpha to guide the self-assembly of calcite "spicules" similar to the spicules of the calcareous sponge Sycon sp. The self-assembled spicules, 10 to 300 micrometers (mu m) in length and 5 to 10 mu m in diameter, are composed of aligned calcite nanocrystals. The spicules are initially amorphous but transform into calcite within months, exhibiting unusual growth along [100]. They scatter x-rays like twinned calcite crystals. Whereas natural spicules evidence brittle failure, the synthetic spicules show an elastic response, which greatly enhances bending strength. This remarkable feature is linked to a high protein content. With nano-thermogravimetric analysis, we measured the organic content of a single spicule to be 10 to 16%. In addition, the spicules exhibit waveguiding properties even when they are bent.
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(2013) Dalton Transactions. 42, 15, p. 5292-5297 Abstract
Enlightened by the discovery of graphenes, a variety of inorganic analogues have been synthesized and characterized in recent years. Solvated Nb1-xWxS2 analogues of graphene-type sheets were prepared by lithiation and exfoliation of multistacked Nb1-xWxS2 coin roll nanowires (CRNWs), followed by in situ functionalization with gold nanoparticles to synthesize gold-loaded Nb1-xWxS2/Au nanocomposites. The Nb1-xWxS2 nanosheets and the corresponding Nb1-xWxS2/Au nanocomposites were characterized by high resolution electron microscopy (HRTEM), energy-dispersive X-ray spectroscopy (EDX), scanning transmission electron microscopy (STEM), dynamic light scattering (DLS) and scanning force microscopy (AFM). The graphene-type sheets are stable in water and other solvents and can be functionalized similarly as chalcogen-terminated surfaces (e.g. with Au nanoparticles).
[All authors] -
(2013) Nanoscale. 5, 8, p. 3447-3456 Abstract
Conventional vapor-deposition techniques for coatings require sophisticated equipment and/or high-temperature resistant substrates. Therefore bio-inspired techniques for the fabrication of inorganic coatings have been developed in recent years. Inspired by the biology behind the formation of the intricate skeletons of diatoms orchestrated by a class of cationic polyamines (silaffins) we have used surface-bound spermine, a naturally occurring polyamine, to promote the fast deposition of homogeneous, thin and transparent biomimetic SnO2 coatings on glass surfaces. The bio-enabled SnO2 film is highly photoactive, i.e. it generates superoxide radicals (O-2(-)) upon sunlight exposure resulting in a strong degradation of organic contaminants and a strong antimicrobial activity. Upon illumination the biomimetic SnO2 coating exhibits a switchable amphiphilic behavior, which - in combination with its photoactivity - creates a self-cleaning surface. The intrinsic self-cleaning properties could lead to the development of new protective, antifouling coatings on various substrates.
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(2013) Nanoscale. 5, 20, p. 9944-9949 Abstract
Colloidal Au@ZnO hybrid nanocrystals with linear and branched shape were synthesized. The number of ZnO domains on the Au seeds can be controlled by the solvent mixture. Imidazole-functionalized Au@ZnO hybrid nanocrystals were soluble in water and exhibited a greatly enhanced photocatalytic activity compared to ZnO nanocrystals. The pristine heterodimeric NPs were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-Vis spectroscopy.
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2012
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(2012) Nature Nanotechnology. 7, 8, p. 530-535 Abstract
Marine biofouling-the colonization of small marine microorganisms on surfaces that are directly exposed to seawater, such as ships' hulls-is an expensive problem that is currently without an environmentally compatible solution(1). Biofouling leads to increased hydrodynamic drag, which, in turn, causes increased fuel consumption and greenhouse gas emissions. Tributyltin-free antifouling coatings and paints(1-4) based on metal complexes or biocides have been shown to efficiently prevent marine biofouling. However, these materials can damage(5) the environment through metal leaching (for example, of copper and zinc)(6) and bacteria resistance(7). Here, we show that vanadium pentoxide nanowires act like naturally occurring vanadium haloperoxidases(8) to prevent marine biofouling. In the presence of bromide ions and hydrogen peroxide, the nanowires catalyse the oxidation of bromide ions to hypobromous acid (HOBr). Singlet molecular oxygen (O-1(2)) is formed and this exerts strong antibacterial activity, which prevents marine biofouling without being toxic to marine biota. Vanadium pentoxide nanowires have the potential to be an alternative approach to conventional anti-biofouling agents.
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(2012) FEBS Journal. 279, 10, p. 1737-1749 Abstract
Owing to their physical and chemical properties, inorganic functional materials have tremendous impacts on key technologies such as energy generation and storage, information, medicine, and automotive engineering. Nature, on the other hand, provides evolution-optimized processes, which lead to multifunctional inorganicbio-organic materials with complex structures. Their formation occurs under physiological conditions, and is goverened by a combination of highly regulated biological processes and intrinsic chemical properties. Nevertheless, insights into the molecular mechanisms of biomineralization open up promising perspectives for bioinspired and biomimetic design and the development of inorganicbio-organic multifunctional hybrids. Therefore, biomimetic approaches may disclose new synthetic routes under ambient conditions by integrating the concept of gene-regulated biomineralization principles. The skeletal structures of marine sponges provide an interesting example of biosilicification via enzymatically controlled and gene-regulated silica metabolism. Spicule formation is initiated intracellularly by a fine-tuned genetic mechanism, which involves silica deposition in vesicles (silicassomes) under the control of the enzyme silicatein, which has both catalytic and templating functions. In this review, we place an emphasis on the fabrication of biologically inspired materials with silicatein as a biocatalyst.
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(2012) Nanoscale. 4, 15, p. 4680-4686 Abstract
A convenient and simple strategy for preparing water soluble, photoluminescent functionalized silica nanoparticles (M-dots) in the absence of fluorophores or metal doping is demonstrated. These M-dots can be used for bioimaging using one and two-photon microscopy. Because of their high photostability, low toxicity and high biocompatibility compared with Lumidot (TM) CdSe/ZnS quantum dots, functionalized silica particles are superior alternatives for current bioimaging platforms. Moreover, the presence of a free amine group at the surface of the M-dots allows biomolecule conjugation (e. g. with antibodies, proteins) in a single step for converting these photoluminescent SiO2 nanoparticles into multifunctional efficient vehicles for theragnostics.
[All authors] -
(2012) Nanoscale. 4, 15, p. 4571-4577 Abstract
Ni@Fe2O3 heterodimer nanoparticles (NPs) were synthesized by thermal decomposition of organometallic reactants. After functionalization, these Ni@Fe2O3 heterodimers became water soluble. The pristine heterodimeric NPs were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), Mossbauer spectroscopy and magnetic susceptibility measurements. A special advantage of the heterodimers lies in the fact that nanodomains of different composition can be used as catalysts for the removal of environmentally hazardous halogenated pollutants.
[All authors] -
(2012) Journal of Materials Chemistry. 22, 18, p. 9253-9262 Abstract
Highly biocompatible multifunctional nanocomposites consisting of monodisperse manganese oxide nanoparticles with luminescent silica shells were synthesized by a combination of w/o-microemulsion techniques and common sol-gel procedures. The nanoparticles were characterized by TEM analysis, powder XRD, SQUID magnetometry, FT-IR, UV/vis and fluorescence spectroscopy and dynamic light scattering. Due to the presence of hydrophilic poly(ethylene glycol) (PEG) chains on the SiO2 surface, the nanocomposites are highly soluble and stable in various aqueous solutions, including physiological saline, buffer solutions and human blood serum. The average number of surface amino groups available for ligand binding on the particles was determined using a colorimetric assay with fluorescein isothiocyanate (FITC). This quantification is crucial for the drug loading capacity of the nanoparticles. SiO2 encapsulated MnO@SiO2 nanoparticles were less prone to Mn-leaching compared to nanoparticles coated with a conventional bi-functional dopamine PEG ligand. The presence of a silica shell did not change the magnetic properties significantly, and therefore, the MnO@SiO2 nanocomposite particles showed a T-1 contrast with relaxivity values comparable to those of PEGylated MnO nanoparticles. The cytotoxicity of the MnO@SiO2-PEG/NH2 nanoparticles was evaluated using primary cells of the innate immune system with bone marrow-derived polymorphonuclear neutrophils (BM-PMNs) as import phagocytes in the first line of defence against microbial pathogens, and bone marrow-derived dendritic cells (BMDCs), major regulators of the adaptive immunity. MnO@SiO2-PEG/NH2 nanoparticles have an acceptable toxicity profile and do not interact with BMDCs as shown by the lack of activation and uptake.
[All authors] -
(2012) Journal of Materials Chemistry. 22, 18, p. 8826-8834 Abstract
Initiation of pathways that lead to a proliferation and chemoresistance by Toll-like receptors (TLRs) are an important factor in cancer progression. Multifunctional magnetic nanoparticles equipped with a pathogen-derived ligand (CpG) functioning as TLR agonists were used to show the impact of immune activation on human HNSCC (head and neck squamous cell carcinoma) cells. The response of human cancer cells to TLR signaling is linked to tumor biology. The magnetic MnO nanoparticles were coated with a multifunctional polymer, displaying no cytotoxicity and being able to enter cells while carrying foreign DNA (unmethylated CpG) to recognize intracellular TLR9. Both the particle and the nucleic acid were tagged with fluorescent markers for simultaneous visualization inside the cell. Cell and animal studies show that the multimodal nanoparticles used as a TLR carrier system allow monitoring simultaneously nanoparticle cellular trafficking and transport by optical and MRI imaging.
[All authors] -
(2012) Faraday Discussions. 159, p. 433-448 Abstract
The calcitic prisms of Pinna nobilis (Pinnidae, Linnaeus 1758) are shown to be perfect examples of a mesocrystalline material. Based on their ultrastructure and on the occurrence of an amorphous transient precursor during the early stages of prism formation, we provide evidence for the pathway of mesocrystallisation proposed by Seto et al. (2012), which proceeds not by self-organized oriented attachment of crystalline nano-bricks but by aggregation of initially amorphous nanogranules which later transform by epitaxial nucleation to a three-dimensional array of well aligned nanocrystals. We further fathom the role of a liquid amorphous calcium carbonate in biomineralisation processes and provide strong evidence for the occurrence of PILP-like intermediates during prism formation. We develop a new scenario of prism formation based on the presented findings presented findings and discuss the implications of a speculative liquid amorphous calcium carbonate (LACC) intermediate in vivo.
2011
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Biocatalytic formation of synthetic melanin: The role of vanadium haloperoxidases, L-DOPA and iodide(2011) Journal of Inorganic Biochemistry. 105, 6, p. 887-893 Abstract
The vanadium haloperoxidase (V-HPO) enzyme, extracted from the brown alga Laminaria saccharina, is able to catalyze the formation of a black precipitate, using as precursor the amino add L-dopa in the presence of hydrogen peroxide and iodide, in one-pot synthesis. The L-dopa oxidation is a multistep reaction with a crucial role played by the iodide in the enzyme catalyzed peroxidative production of dopachrome, a well known intermediate in the synthesis of melanin. Dopachrome is then converted to a synthetic form of melanin through a polymerization reaction. Factors, such as buffer composition and pH, influence significantly the reaction first steps, but further steps of melanin production are hardly influenced. The biosynthetic melanin produced through the combination V-HPO/1/H(2)O(2), was characterized by several spectroscopic techniques (UV-vis and FT-IR) as well as XRD. Moreover, this biopolymer is light sensitive, decomposing into oligo- and monomeric units. Scanning electron microscopy (SEM) imaging showed different morphologies when compared with commercial available melanin. The biosynthetic production of melanin can have a wide range of applications from photosensitive cells to biomedicine with the advantage of being produced under eco-friendly and mild conditions. (C) 2011 Elsevier Inc. All rights reserved.
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(2011) Journal of Experimental Biology. 214, 10, p. 1748-1753 Abstract
The metabolic energy state of sponge tissue in vivo is largely unknown. Quantitative bioluminescence-based imaging was used to analyze the ATP distribution of Suberites domuncula (Olivi 1792) tissue, in relation to differences between the cortex and the medulla. This method provides a quantitative picture of the ATP distribution closely reflecting the in vivo situation. The obtained data suggest that the highest ATP content occurs around channels in the sponge medulla. HPLC reverse-phase C-18, used for measurement of ATP content, established a value of 1.62 mu molATPg(-1) dry mass in sponge medulla, as opposed to 0.04 mu molATPg(-1) dry mass in the cortex, thus indicating a specific and defined energy distribution. These results correlate with the mitochondria localization, determined using primary antibodies against cytochrome oxidase c subunit 1 (COX1) (immunostaining), as well as with the distribution of arginine kinase (AK), essential for cellular energy metabolism (in situ hybridization with AK from S. domuncula; SDAK), in sponge sections. The highest energy consumption seemed to occur in choanocytes, the cells that drive the water through the channel system of the sponge body. Taken together, these results showed that the majority of energetic metabolism in S. domuncula occurs in the medulla, in the proximity of aqueous channels.
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(2011) Advanced Functional Materials. 21, 3, p. 501-509 Abstract
V2O5 nanowires exhibit an intrinsic catalytic activity towards classical peroxidase substrates such as 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 3,3,5,5,-tetramethylbenzdine (TMB) in the presence of H2O2. These V2O5 nanowires show an optimum reactivity at a pH of 4.0 and the catalytic activity is dependent on the concentration. The Michaelis-Menten kinetics of the ABTS oxidation over these nanowires reveals a behavior similar to that of their natural vanadium-dependent haloperoxidase (V-HPO) counterparts. The V2O5 nanowires mediate the oxidation of ABTS in the presence of H2O2 with a turnover frequency (k(cat)) of 2.5 x 10(3) s(-1). The K-M values of the V2O5 nanowires for ABTS oxidation (0.4 mu M) and for H2O2 (2.9 mu M) at a pH of 4.0 are significantly smaller than those reported for horseradish peroxidases (HRP) and V-HPO indicating a higher affinity of the substrates for the V2O5 nanowire surface. Based on the kinetic parameters and similarity with vanadium-based complexes a mechanism is proposed where an intermediate metastable peroxo complex is formed as the first catalytic step. The nanostructured vanadium-based material can be re-used up to 10 times and retains its catalytic activity in a wide range of organic solvents (up to 90%) making it a promising mimic of peroxidase catalysts.
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(2011) Nanoscale. 3, 9, p. 3907-3914 Abstract
We describe the reconstitution of apo-horse radish peroxidase (apo-HRP) onto TiO2 nanorods functionalized with a multifunctional polymer. After functionalization, the horse radish peroxidase (HRP) functionalized TiO2 nanorods were well dispersible in aqueous solution, catalytically active and biocompatible, and they could be used to quantify and image H2O2 which is a harmful secondary product of cellular metabolism. The shape, size and structure of TiO2 nanorods (anatase) were analyzed by transmission electron microscopy (TEM), high resolution TEM (HRTEM), electron diffraction (ED) and X-ray diffraction (XRD). The surface functionalization, HRP reconstitution and catalytic activity were confirmed by UV-Vis, FT-IR, CLSM and atomic force microscopy (AFM). Biocompatibility and cellular internalization of active HRP reconstituted TiO2 nanorods were confirmed by a classical MTT cytotoxicity assay and confocal laser scanning microscopy (CLSM) imaging, respectively. The intracellular localization allowed H2O2 detection, imaging and quantification in HeLa cells. The polymer functionalized hybrid system creates a complete sensor including a "cell positioning system'' in each single particle. The flexible synthetic concept with functionalization by post-polymerization modification allows introduction of various dyes for sensitisation at different wavelengths and introduction of various anchor groups for anchoring on different particles.
[All authors] -
(2011) Journal of Materials Chemistry. 21, 32, p. 11923-11929 Abstract
V2O5 nanowires act as biomimetic catalysts resembling vanadium haloperoxidases (V-HPO). The nanowires display iodinating activity as confirmed by a colorimetric assay using thymol blue (TB), UV/Vis spectrophotometry and mass spectrometry (FD-MS). In the presence of dopamine these nanowires catalyze the fast and efficient synthesis of melanin-like biopolymers under mild conditions (aqueous solution, neutral pH and room temperature). The resulting melanin-like biopolymer obtained by the V2O5 nanowire catalysts was characterized by scanning electron microscopy (SEM), X-ray diffraction, UV-Vis, FT-IR and electric conductivity resembling the natural biopolymer both in its chemical and morphological features. In addition, this synthetic biopolymer self-assembles into fibril-like structures by forming stacks due to p interactions between the aromatic rings.
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(2011) Journal of Materials Chemistry. 21, 24, p. 8605-8611 Abstract
Cu@Fe3O4 heteroparticles with distinct morphologies were synthesized from organometallic reactants. The shape of the magnetic domains could be controlled by the solvent and reaction conditions. They display magnetic and optical properties that are useful for simultaneous magnetic and optical detection. After functionalization, the Cu@Fe3O4 heterodimers become water soluble. The morphology, structure, magnetic and optical properties of the as-synthesized heterodimer nanoparticles were characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), mossbauer spectroscopy, superconducting quantum interference device (SQUID) magnetometry, and dark field imaging. A special advantage of these heterodimers lies in the fact that the nanodomains of different composition can be used e.g. for the formation of nitric oxide (NO) through the Cu domain and heterodimer nanoparticles can be removed from the reaction mixture by means of the magnetic domain (Fe3O4).
[All authors]
2010
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(2010) Advanced Engineering Materials. 12, 9, p. B438-B450 Abstract
The gold standard for bone reconstruction is the use of autogeneic grafts from various donor regions, since they possess osteoinductive as well as osteoconductive potential. Only a few synthetic materials possess/display properties that allow optimal bone reconstitution. Previously, we showed that the natural product, bio-silica, comprises osteoinductive, and probably also osteoconductive activity. Bio-silica is formed enzymatically via silicatein; this enzyme has been isolated from siliceous sponges and has also been cloned and prepared recombinantly. In the present study, silicatein was encapsulated together with its substrate, sodium metasilicate, in poly(D, L-lactide)/poly(vinyl pyrrolidone)-based microspheres, termed silicatein-and-silica-containing microspheres (SSMs). The deposition of silica and the kinetics of silicatein release from the microspheres are given. Furthermore, SSMs were successfully embedded in a poly(vinyl pyrrolidone)/starch-based matrix, termed plastic-like filler matrix containing silicic acid (PMSA). A blend of SSM and PMSA forms a biocompatible, moldable, and biodegradable functional implant material that hardens at a controlled and clinically suitable rate within approximately 30 min to 6 h to implants that were tightly integrated in artificial defects of rabbit femurs. Until now no toxic reactions caused by the silicatein have been observed in vitro or in vivo. We assume that the data given here contribute to a successful introduction of the silicatein/bio-silica-based implant materials to the field of regenerative medicine.
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(2010) Acta Biomaterialia. 6, 9, p. 3720-3728 Abstract
Since its discovery, numerous biotechnological approaches have aimed to explore the silica-polymerizing catalytic activity of the enzyme silicatein. In vivo, silicatein catalyzes polymerization of amorphous silica nanospheres from soluble precursors. In vitro, it directs the formation of nanostructured biosilica. This is of interest for various applications that strive to benefit from both the advantages of the biological system (i.e., silica synthesis under physiological conditions) and the cell mineralization-stimulating effect of biosilica. However, so far immobilization of silicatein has been hampered by the complex multistep procedure required. In addition, the chemical surface modifications involved not only restrict the choice of carrier materials but also render application of silicatein to hydroxyapatite (HA) of mineralized tissue impossible. Here we describe the bioengineering of silicatein, adapted for application in the fields of bone regeneration, tissue engineering, and dental care. Inspired by Glu-rich sequences of mammalian proteins that confer binding affinity to HA, a novel protein-tag was developed, the Glu-tag. Following expression of Glu-tagged silicatein, the HA-binding capacity of the enzyme is demonstrated in combination with synthetic and dental HA. Furthermore, immobilized Glu-tagged silicatein catalyzes synthesis of biosilica coatings on both synthetic HA nanofibrils and dental HA. Hence, Glu-tagged silicatein reveals a considerable biomedical potential with regenerative and prophylactic implementations. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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(2010) Cell and Tissue Research. 339, 2, p. 429-436 Abstract
Primmorphs (a three-dimensional sponge primary cell culture system) have been revealed to be a cell/tissue nano-factory for the production of tailor-made hybrid nanostructures. Growth of primmorphs is stimulated by the presence of a titanium alkoxide precursor tolerating titania (TiO2) concentrations up to 250 mu M. The presence and activity of silicatein in primmorphs has been analyzed by gel electrophoresis and Western blotting. Results of studies by scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy have revealed silica and titania to be co-localized on nanosized spicules. Our findings suggest that the incorporation of titania into the nanosized spicule is enzymatically mediated via active silicatein in an orchestrated mechanism.
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(2010) Journal of Materials Chemistry. 20, 38, p. 8297-8304 Abstract
Superparamagnetic MnO nanoparticles were functionalized using a hydrophilic ligand containing protoporphyrin IX as photosensitizer. By virtue of their magnetic properties these nanoparticles may serve as contrast enhancing agents for magnetic resonance imaging (MRI), while the fluorescent target ligand protoporphyrin IX allows simultaneous tumor detection and treatment by photodynamic therapy (PDT). Caki-1 cells were incubated with these nanoparticles. Subsequent exposure to UV light lead to cell apoptosis due to photoactivation of the photosensitizer conjugated to the nanoparticles. This method offers great diagnostic potential for highly proliferative tissues, including tumors. In addition, it is an efficient platform that combines the advantages of a biocompatible photosensitizer with the possibility for MRI monitoring due to the magnetic properties of the highly soluble functionalized manganese oxide nanoparticles.
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(2010) Angewandte Chemie - International Edition. 49, 23, p. 3976-3980 Abstract
Flower power: A convenient strategy for preparing core-tunable multicomponent Au@MnO nanocrystals has been developed. The magnetic nanoflowers are not only efficient as cargo-specific carriers but also have excellent fluorescent properties resulting from fluorophors bound to the Au and MnO domains. (Figure Equotion Present)
[All authors]
2009
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(2009) Advanced Functional Materials. 19, 23, p. 3717-3725 Abstract
Here, design of the first pathogen-mimicking metal oxide nanoparticles with the ability to enter cancer cells and to selectively target and activate the TLR9 pathway, and with optical and MR imaging capabilities, is reported. The immobilization of ssDNA (CpG ODN 2006) on MnO nanoparticles is performed via the phosphoramidite route using a multifunctional polymer. The multifunctional polymer used for the nanoparticle surface modification not only affords a protective organic biocompatible shell but also provides an efficient and convenient means for loading immunostimulatory oligonucleotides. Since fluorescent molecules are amenable to photodetection, a chromophore (Rhodamine) is introduced into the polymer chain to trace the nanoparticles in Caki-1 (human kidney cancer) cells. The ssDNA coupled nanoparticles are used to target Toll-like receptors 9 (TLR9) receptors inside the cells and to activate the classical TLR cascade. The presence of TLR9 is demonstrated independently in the Caki-1 cell line by western blotting and immunostaining techniques. The magnetic properties of the MnO core make functionalized MnO nanoparticles potential diagnostic agents for magnetic resonance imaging (MRI) thereby enabling multimodal detection by a combination of MR and optical imaging methods. The trimodal nanoparticles allow the imaging of cellular trafficking by different means and simultaneously are an effective drug carrier system.
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(2009) Comparative Biochemistry and Physiology - B Biochemistry and Molecular Biology. 154, 1, p. 102-107 Abstract
Previously, the cDNA and the respective gene for a presumed tauropine dehydrogenase (TaDH) from Suberites domuncula (GenBank accession nos. AM712888, AM712889) had been annotated. The conclusion that the sequences encode a TaDH had been inferred from the 68% identity with the TaDH protein from the marine demosponge Halichondria japonica. However, subsequent enzymatic assays shown here indicate that the presumed S. domuncula opine dehydrogenase is in fact a strombine dehydrogenase (StDH). The enzyme StDH is highly specific for glycine and is inhibited by an excess of the substrate pyruvate. Besides kinetic data, we report in this study also on the predicted tertiary and quaternary structure of the sponge StDH. It is concluded that the dimer (75 kDa) has a novel structure, distinguishing it from other known marine invertebrate OpDHs that exist as monomers. (C) 2009 Elsevier Inc. All rights reserved.
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(2009) Applied Microbiology and Biotechnology. 83, 3, p. 397-413 Abstract[All authors]
While most forms of multicellular life have developed a calcium-based skeleton, a few specialized organisms complement their body plan with silica. However, of all recent animals, only sponges (phylum Porifera) are able to polymerize silica enzymatically mediated in order to generate massive siliceous skeletal elements (spicules) during a unique reaction, at ambient temperature and pressure. During this biomineralization process (i.e., biosilicification) hydrated, amorphous silica is deposited within highly specialized sponge cells, ultimately resulting in structures that range in size from micrometers to meters. Spicules lend structural stability to the sponge body, deter predators, and transmit light similar to optic fibers. This peculiar phenomenon has been comprehensively studied in recent years and in several approaches, the molecular background was explored to create tools that might be employed for novel bioinspired biotechnological and biomedical applications. Thus, it was discovered that spiculogenesis is mediated by the enzyme silicatein and starts intracellularly. The resulting silica nanoparticles fuse and subsequently form concentric lamellar layers around a central protein filament, consisting of silicatein and the scaffold protein silintaphin-1. Once the growing spicule is extruded into the extracellular space, it obtains final size and shape. Again, this process is mediated by silicatein and silintaphin-1, in combination with other molecules such as galectin and collagen. The molecular toolbox generated so far allows the fabrication of novel micro- and nanostructured composites, contributing to the economical and sustainable synthesis of biomaterials with unique characteristics. In this context, first bioinspired approaches implement recombinant silicatein and silintaphin-1 for applications in the field of biomedicine (biosilica-mediated regeneration of tooth and bone defects) or micro-optics (in vitro synthesis of light waveguides) with promising results.
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(2009) ChemBioChem. 10, 4, p. 683-689 Abstract
High-resolution microscopy shows that during the initial stages of demosponge spicule formation, a primordial crystalline structure is formed within the axial filament. The recently developed electron diffraction tomography technique reveals that the nanorods have a layered structure that matches smectitic phyllosilicates. These intracellular nanorods have been considered as precursors of mature spicules.
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(2009) Biomaterials. 30, 8, p. 1648-1656 Abstract
Biosilicification in sponges is initiated by formation of proteinaceous filaments, predominantly consisting of silicateins. Silicateins enzymatically catalyze condensation of silica nanospheres, resulting in symmetric skeletal elements (spicules). In order to create tailored biosilica structures in biomimetic approaches it is mandatory to elucidate proteins that are fundamental for the assembly of filaments. Silintaphin-1 is a core component of modularized filaments and also part of a spicule-enfolcling layer. It bears no resemblance to other proteins, except for the presence of ail interaction domain that is fundamental for its function as scaffold/template. In the presence of silicatein silintaphin-1 facilitates the formation of in vitro filaments. Also, it directs the assembly of gamma-Fe(2)O(3) nanoparticles and surface-immobilized silicatein to rod-like biocomposites, synthetic spicules. Thus, silintaphin-1 will contribute to biomimetic approaches that Pursue a controlled formation of patterned biosilica-based materials. Its combination with gamma-Fe(2)O(3) nanoparticles and immobilized silicatein will furthermore inspire future biomedical applications and clinical diagnostics. (C) 2008 Elsevier Ltd. All rights reserved.
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(2009) Micron. 40, 5-6, p. 526-535 Abstract
Ferromanganese [Fe/Mn] crusts formed on basaltic seamounts, gain considerable economic importance due to their high content of Co, Ni, Cu, Zn and Pt. The deposits are predominantly found in the Pacific Ocean in depths of over 1000 m. They are formed in the mixing layer between the upper oxygen-minimum zone and the lower oxygen-rich bottom zone. At present an almost exclusive abiogenic origin of crust formation is considered. We present evidence that the upper layers of the crusts from the Magellan Seamount cluster are very rich in coccoliths/coccolithophores (calcareous phytoplankton) belonging to different taxa. Rarely intact skeletons of these unicellular algae are found, while most of them are disintegrated into their composing prisms or crystals. Studies on the chemical composition of crust samples by high resolution SEM combined with an electron probe microanalyzer (EPMA) revealed that they are built of distinct stacked piles of individual compartments. in the center of such piles Mn is the dominant element, while the rims of the piles are rich in Fe (MINERALIZATION aspect). The compartments contain coccospheres usually at the basal part. Energy dispersive X-ray spectroscopy (EDX) analyses showed that those coccospheres contain, as expected, CaCO(3) but also Mn-oxide. Detailed analysis displayed on the surface of the coccolithophores a high level of CaCO(3) while the concentration of Mn-oxide is relatively small. With increasing distance from the coccolithophores the concentration of Mn-oxide increases on the expense of residual CaCO(3). We conclude that coccoliths/coccolithophores are crucial for the seed/nucleation phase of crust formation (BIOMINERALIZATION aspect). Subsequently, after the biologically induced mineralization phase Mn-oxide deposition proceeds "auto"catalytically. (C) 2009 Elsevier Ltd. All rights reserved.
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(2009) Advanced Functional Materials. 19, 2, p. 285-291 Abstract
A chemically specific and facile method for the biofunctionalization of WS2 nanotubes (NT-WS2) is reported. The covalent modification strategy is based on the affinity of the nitrilotriacetic acid (NTA) side chain, which serves as a ligand for the surface binding to NT-WS2 and simultaneously as an anchor group for the binding of His-tagged proteins to the polymer backbone. The polymer functionalized WS2 nanotubes can be solubilized either in water or organic solvents; they are stable for at least one week. The probes were characterized by FT-IR and UV-vis spectroscopy. The immobilization of silicatein, a hydrolytic protein encountered in marine sponges, was visualized by scanning force microscopy (SFM) and confocal laser scanning microscopy (CLSM). The formation of the biotitania coating mediated by the immobilized silicatein onto the surface was characterized by scanning electron microscopy (SEM), and transmission electron microscopy (TEM).
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(2009) Biosilica in Evolution, Morphogenesis, and Nanobiotechnology. p. 251-273 Abstract
Silica-based materials are used in many high-tech products including microelectronics, optoelectronics, and catalysts. Siliceous sponges (Demospongiae and Hexactinellida) are unique in their ability to synthesize silica enzymatically. We have cloned the silica-forming enzymes, silicateins, from both demosponges (marine and freshwater sponges) and hexactinellid sponges. The recombinant enzymes allow the synthesis of silica under environmentally benign ambient conditions, while the technical (chemical) production of silica commonly requires high temperatures and pressures, and extremes of pH. Silicateins can be used for the fabrication of highly-ordered inorganic-organic composite materials with defined optical, electrical, and mechanical properties. The simple self-assembly properties of silicateins which are able to form silica and other metal oxides in aqueous solution allow the development of novel products in nano(bio)technology, medicine, and dentistry.
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(2009) Soft Matter. 5, 19, p. 3657-3662 Abstract
We describe the self-assembly of discrete SiO(2) nanofibers via grafting of silicatein side chains to a polymer backbone. The covalent binding of silicatein to the backbone of the polymer is based on the affinity of the nitrilotriacetic acid (NTA) side chain, which serves as a ligand for the immobilization of His-tagged silicatein. The surface charge and the bulkiness of the protein moieties prevent the entropically favoured coil formation of the polymer and force it to adopt an open chain structure after hydrolysis of the silica precursors. The probes were characterized by scanning force microscopy (SFM) and optical light microscopy. Surface complexation of the resulting silica nanoparticles by the polymer-bound silicatein were analysed using high resolution tranmission electron microscopy (HRTEM).
2008
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(2008) Journal of Magnetism and Magnetic Materials. 320, 19, p. 2339-2344 Abstract
Multifunctional polymer-derivatized superparamagnetic iron oxide (gamma-Fe(2)O(3)) nanoparticles were prepared for biomagnetic separation of histidine-tagged recombinant proteins building up a faster and efficient method for protein separation by making use of their intrinsic magnetic properties. Using polymer bound gamma-Fe(2)O(3) nanocrystals, a 6 x histidine-tagged recombinant protein (silicatein) with a molecular weight of 24 kDa has been isolated and purified. The supermagnetic iron oxide nanocrystals were characterized by transmission electron microscopy (TEM), high-resolution TEM (HRTEM), SQUID and Mossbauer and the polymer functionalization of the gamma-Fe(2)O(3) nanocrystals was monitored by UV-vis spectroscopy and light microscopy. Protein immobilization and separation was monitored using immunostaining techniques and gel electrophoresis, respectively. (C) 2008 Elsevier B.V. All rights reserved.
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(2008) Chemistry of Materials. 20, 11, p. 3567-3573 Abstract
Silicatein, a hydrolytic protein encountered in marine sponges, was immobilized on maghemite (gamma-Fe2O3) nanoparticles that were surface functionalized with a reactive mulfunctional polymer. This polymer carries an anchor group based on dopamine which is capable of binding to the gamma-Fe2O3 Surface and a reactive functional group which allows binding of various biomolecules onto inorganic nanoparticles. This functional nitrilotriacetic acid (NTA) group allows immobilization of His-tagged silicatein on the surface of the gamma-Fe2O3 nanoparticles. The surface-bound protein retains its native hydrolytic activity to catalyze formation of silica through copolymerization of alkoxysilanes Si(OR)(4). Functionalization of the magnetic nanoparticles and the architecture of the SiO2-coated gamma-Fe2O3 nanoparticles was confirmed by TEM studies as well as by FT-IR and optical microscopy.
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(2008) Molecular Immunology. 45, 4, p. 945-953 Abstract
Aquatic animals, especially filter feeders such as sponges [phylum Porifera], are exposed to a higher viral load than terrestrial species. Until now, the antiviral defense system in the evolutionary oldest multicellular organisms, sponges, is not understood. One powerful protection of vertebrates against virus infection is mediated by the interferon (IFN)-inducible 2'-5'-oligoadenylate synthetase [(2-5)A synthetase] system. In the present study we cloned from the freshwater sponge Lubomirskia baicalensis a cDNA encoding a 314 as long ORF with a calculated size of 35748 Da, a putative (2-5)A synthetase, and raised antibodies against the recombinant protein. The native enzyme was identified in a crude extract from L. baicalensis by application of a novel separation procedure based on polymer coated ferromagnetic nanoparticles. The particles were derivatized with a synthetic double-stranded RNA [dsRNA], synthetic poly(I:C), a known allosteric activator of the latent (2-5)A synthetase. These particles were used to separate a single 35 kDa protein from a crude extract of L. baicalensis, which cross-reacted with antibodies raised against the sponge enzyme. In situ hybridization studies revealed that highest expression of the gene is seen in cells surrounding the aquiferous canals. Finally primmorphs, an in vitro cell culture system, from L. baicalensis were exposed to poly(I:C); they responded to this dsRNA with an increased expression of the (2-5)A synthetase gene already after a 1-day incubation period. We conclude that sponges contain the (2-5)A synthetase antiviral protection system. (c) 2007 Elsevier Ltd. All rights reserved.
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(2008) Biotechnology Advances. 26, 3, p. 233-245 Abstract
An appreciation of the potential applications of molecular biology is of growing importance in many areas of life sciences, including marine biology. During the past two decades, the development of sophisticated molecular technologies and instruments for biomedical research has resulted in significant advances in the biological sciences. However, the value of molecular techniques for addressing problems in marine biology has only recently begun to be cherished. It has been proven that the exploitation of molecular biological techniques will allow difficult research questions about marine organisms and ocean processes to be addressed. Marine molecular biology is a discipline, which strives to define and solve the problems regarding the sustainable exploration of marine life for human health and welfare, through the cooperation between scientists working in marine biology, molecular biology, microbiology and chemistry disciplines. Several success stories of the applications of molecular techniques in the field of marine biology are guiding further research in this area. In this review different molecular techniques are discussed, which have application in marine microbiology, marine invertebrate biology, marine ecology, marine natural products, material sciences, fisheries, conservation and bio-invasion etc. In summary, if marine biologists and molecular biologists continue to work towards strong partnership during the next decade and recognize intellectual and technological advantages and benefits of such partnership, an exciting new frontier of marine molecular biology will emerge in the future. (C) 2008 Elsevier Inc. All rights reserved.
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(2008) Angewandte Chemie - International Edition. 47, 25, p. 4748-4752 Abstract
(Figure Presented) Specific cell recognition: Magnetic g-Fe 2O3 nanoparticles (MNPs) functionalized with a fluorescently labeled polymer and polyinosinic-polycytidylic acid [poly-(I:C)] allow the specific visualizion of the TLR3 receptors on the the surface of Caki-1 cells. The expression of TLR3 on the Caki-1 cells was demonstrated independently by RT-PCR and immunostaining techniques.
[All authors] -
NanoBio-Tools for Selective Activation of Toll-like receptors (TLRs)(2008) NSTI NANOTECH 2008, VOL 2, TECHNICAL PROCEEDINGS. Romanowicz B. & Laudon M.(eds.). p. 505-508 Abstract
The immobilization of polyinosinic-polycytidylic acid [poly(I:C)] on gamma-Fe2O3 nanoparticles via the phosphoramidate route using a multifunctional polymer is reported. The dsRNA coupled nanoparticles were used to visualize the Toll-like (TLR3) receptors at the cell surface. The presence of TLR3 was demonstrated independently in the Caki-1 cell line by RT-PCR and immunostaining techniques.
[All authors]
2007
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(2007) Journal of Structural Biology. 159, 3, p. 325-334 Abstract
Recently it has been discovered that the formation of the siliceous spicules of Demospongiae proceeds enzymatically (via silicatein) and occurs matrix guided (on galectin strings). In addition, it could be demonstrated that silicatein, if immobilized onto inorganic surfaces, provides the template for the synthesis of biosilica. In order to understand the formation of spicules in the intact organism, detailed studies with primmorphs from Suberites domuncula have been performed. The demosponge spicules are formed from several silica lamellae which are concentrically arranged around the axial canal, harboring the axial filament composed of silicatein. Now we show that the appositional growth of the spicules in radial and longitudinal direction proceeds in the extracellular space along hollow cylinders; their surfaces are formed by silicatein. The extracellularly located spicules are surrounded by sclerocytes which are filled with both electron-dense and electron-poor vesicles; energy dispersive X-ray analysis/scanning electron microscopical studies revealed that the electron-dense vesicles are filled of silicon/silica and therefore termed silicasomes. The release of the content of the silicasomes into the hollow cylinder suggests that the newly formed silica lamella originate there; in addition the data are compatible with the view that the silicatein molecules, attached at the centripetal and centrifugal surfaces, mediate biosilica formation. In a chemical/biomimetical approach silicatein is linked onto the organic material-free spicules after their functionalization with aminopropyltriethoxysilane [amino groups]poly(acetoxime methacrylate) [reactive ester polymer]-N-epsilon-benzyloxycarbonyl L-lysine tert-butyl ester-Ni(II); finally His-tagged silicatein is immobilized. The matrix-bound enzyme synthesized a new biosilica lamella. These bioinspired findings are considered as the basis for a technical use/application/utilization of hollow cylinders formed by matrix-guided silicatein molecules for the biocatalytic synthesis of nanostructured tubes. (c) 2007 Elsevier Inc. All rights reserved.
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(2007) Small. 3, 8, p. 1374-1378 Abstract
Double stranded RNA polyinosinic-polycytidlylic acid (poly(IC)) immobilized onto y-Fe2O3 nanoparticles with the use of a multifunctional polymer linker is analyzed. Among the most potent dsRNAs is the synthetic dsRNA poly(IC), which consists of a pair of strands of polyinosinic and polycytidylic acids. Poly(IC) shows antitumor and anti- viral activity and recently entered into phase II clinical trials for patients with malignant gliomas. The immobilization of biomolecules such as poly(IC) onto insoluble supports or nanoparticles is an important tool for the fabrication of functional materials or devices. Ferrimagnetic y-Fe 2O3 nanoparticles were synthesized by co-precipitation of ferrous and ferric ions in sodium hydroxide solution. The efficiency and stability of binding between the amine-functionalized iron oxide nanoparticles and poly(IC) was studied by electrophoresis.
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(2007) Chemical Communications. 44, p. 4677-4679 Abstract
Polymer coated superparamagnetic gamma-Fe2O3 nanoparticles were derivatized with a synthetic double-stranded RNA [poly(IC)], a known allosteric activator of the latent (2-5) A synthetase, to separate a single 35 kDa protein from a crude extract which cross reacted with antibodies raised against the sponge enzyme.