Tunable Oxidized-Chitin Hydrogels with Customizable Mechanical Properties by Metal or Hydrogen Ion Exposure.

This study focuses on the optimization of chitin oxidation in C6 to carboxylic acid and its use to obtain a hydrogel with tunable resistance. After the optimization, water-soluble crystalline ß-chitin fibrils (ß-chitOx) with a degree of functionalization of 10% were obtained. Diverse reaction conditions were also tested for α-chitin, which showed a lower reactivity and a slower reaction kinetic. After that, a set of hydrogels was synthesized from ß-chitOx 1 wt.% at pH 9, inducing the gelation by sonication. These hydrogels were exposed to different environments, such as different amounts of Ca2+, Na+ or Mg2+ solutions, buffered environments such as pH 9, PBS, pH 5, and pH 1, and pure water. These hydrogels were characterized using rheology, XRPD, SEM, and FT-IR. The notable feature of these hydrogels is their ability to be strengthened through cation chelation, being metal cations or hydrogen ions, with a five- to tenfold increase in their storage modulus (G'). The ions were theorized to alter the hydrogen-bonding network of the polymer and intercalate in chitin's crystal structure along the a-axis. On the other hand, the hydrogel dissolved at pH 9 and pure water. These bio-based tunable hydrogels represent an intriguing material suitable for biomedical applications.

Stearate-Coated Biogenic Calcium Carbonate from Waste Seashells: A Sustainable Plastic Filler.

Waste seashells from aquaculture are a massive source of biogenic calcium carbonate (bCC) that can be a potential substitute for ground calcium carbonate and precipitated calcium carbonate. These last materials find several applications in industry after a surface coating with hydrophobic molecules, with stearate as the most used. Here, we investigate for the first time the capability of aqueous stearate dispersions to coat bCC powders from seashells of market-relevant mollusc aquaculture species, namely the oyster Crassostrea gigas, the scallop Pecten jacobaeus, and the clam Chamelea gallina. The chemical-physical features of bCC were extensively characterized by different analytical techniques. The results of stearate adsorption experiments showed that the oyster shell powder, which is the bCC with a higher content of the organic matrix, showed the highest adsorption capability (about 23 wt % compared to 10 wt % of geogenic calcite). These results agree with the mechanism proposed in the literature in which stearate adsorption mainly involves the formation of calcium stearate micelles in the dispersion before the physical adsorption. The coated bCC from oyster shells was also tested as fillers in an ethylene vinyl acetate compound used for the preparation of shoe soles. The obtained compound showed better mechanical performance than the one prepared using ground calcium. In conclusion, we can state that bCC can replace ground and precipitated calcium carbonate and has a higher stearate adsorbing capability. Moreover, they represent an environmentally friendly and sustainable source of calcium carbonate that organisms produce by high biological control over composition, polymorphism, and crystal texture. These features can be exploited for applications in fields where calcium carbonate with selected features is required.

Nanocrystalline and Amorphous Calcium Carbonate from Waste Seashells by Ball Milling Mechanochemistry Processes.

Nanocrystalline calcium carbonate (CaCO3) and amorphous CaCO3 (ACC) are materials of increasing technological interest. Nowadays, they are mainly synthetically produced by wet reactions using CaCO3 reagents in the presence of stabilizers. However, it has recently been discovered that ACC can be produced by ball milling calcite. Calcite and/or aragonite are the mineral phases of mollusk shells, which are formed from ACC precursors. Here, we investigated the possibility to convert, on a potentially industrial scale, the biogenic CaCO3 (bCC) from waste mollusk seashells into nanocrystalline CaCO3 and ACC. Waste seashells from the aquaculture species, namely oysters (Crassostrea gigas, low-Mg calcite), scallops (Pecten jacobaeus, medium-Mg calcite), and clams (Chamelea gallina, aragonite) were used. The ball milling process was carried out by using different dispersing solvents and potential ACC stabilizers. Structural, morphological, and spectroscopic characterization techniques were used. The results showed that the mechanochemical process produced a reduction of the crystalline domain sizes and formation of ACC domains, which coexisted in microsized aggregates. Interestingly, bCC behaved differently from the geogenic CaCO3 (gCC), and upon long milling times (24 h), the ACC reconverted into crystalline phases. The aging in diverse environments of mechanochemically treated bCC produced a mixture of calcite and aragonite in a species-specific mass ratio, while the ACC from gCC converted only into calcite. In conclusion, this research showed that bCC can produce nanocrystalline CaCO3 and ACC composites or mixtures having species-specific features. These materials can enlarge the already wide fields of applications of CaCO3, which span from medical to material science.

Assembly of the Intraskeletal Coral Organic Matrix during Calcium Carbonate Formation.

Scleractinia coral skeleton formation occurs by a heterogeneous process of nucleation and growth of aragonite in which intraskeletal soluble organic matrix molecules, usually referred to as SOM, play a key role. Several studies have demonstrated that they influence the shape and polymorphic precipitation of calcium carbonate. However, the structural aspects that occur during the growth of aragonite have received less attention. In this research, we study the deposition of calcium carbonate on a model substrate, silicon, in the presence of SOM extracted from the skeleton of two coral species representative of different living habitats and colonization strategies, which we previously characterized. The study is performed mainly by grazing incidence X-ray diffraction with the support of Raman spectroscopy and electron and optical microscopies. The results show that SOM macromolecules once adsorbed on the substrate self-assembled in a layered structure and induced the oriented growth of calcite, inhibiting the formation of vaterite. Differently, when SOM macromolecules were dispersed in solution, they induced the deposition of amorphous calcium carbonate (ACC), still preserving a layered structure. The entity of these effects was species-dependent, in agreement with previous studies. In conclusion, we observed that in the setup required by the experimental procedure, the SOM from corals appears to present a 2D lamellar structure. This structure is preserved when the SOM interacts with ACC but is lost when the interaction occurs with calcite. This knowledge not only is completely new for coral biomineralization but also has strong relevance in the study of biomineralization on other organisms.

Supramolecular Binding with Lectins: A New Route for Non-Covalent Functionalization of Polysaccharide Matrices.

The chemical functionalization of polysaccharides to obtain functional materials has been of great interest in the last decades. This traditional synthetic approach has drawbacks, such as changing the crystallinity of the material or altering its morphology or texture. These modifications are crucial when a biogenic matrix is exploited for its hierarchical structure. In this work, the use of lectins and carbohydrate-binding proteins as supramolecular linkers for polysaccharide functionalization is proposed. As proof of concept, a deproteinized squid pen, a hierarchically-organized ß-chitin matrix, was functionalized using a dye (FITC) labeled lectin; the lectin used was the wheat germ agglutinin (WGA). It has been observed that the binding of this functionalized protein homogenously introduces a new property (fluorescence) into the ß-chitin matrix without altering its crystallographic and hierarchical structure. The supramolecular functionalization of polysaccharides with protein/lectin molecules opens up new routes for the chemical modification of polysaccharides. This novel approach can be of interest in various scientific fields, overcoming the synthetic limits that have hitherto hindered the technological exploitation of polysaccharides-based materials.

Direct Ink Write Printing of Chitin-Based Gel Fibers with Customizable Fibril Alignment, Porosity, and Mechanical Properties for Biomedical Applications.

A fine control over different dimensional scales is a challenging target for material science since it could grant control over many properties of the final material. In this study, we developed a multivariable additive manufacturing process, direct ink write printing, to control different architectural features from the nano- to the millimeter scale during extrusion. Chitin-based gel fibers with a water content of around 1500% were obtained extruding a polymeric solution of chitin into a counter solvent, water, inducing instant solidification of the material. A certain degree of fibrillar alignment was achieved basing on the shear stress induced by the nozzle. In this study we took into account a single variable, the nozzle's internal diameter (NID). In fact, a positive correlation between NID, fibril alignment, and mechanical resistance was observed. A negative correlation with NID was observed with porosity, exposed surface, and lightly with water content. No correlation was observed with maximum elongation (~50%), and the scaffold's excellent biocompatibility, which appeared unaltered. Overall, a single variable allowed a customization of different material features, which could be further tuned, adding control over other aspects of the synthetic process. Moreover, this manufacturing could be potentially applied to any polymer.

Nanoarchitected Tough Biological Composites from Assembled Chitinous Scaffolds.

Over hundreds of millions of years, organisms have derived specific sets of traits in response to common selection pressures that serve as guideposts for optimal biological designs. A prime example is the evolution of toughened structures in disparate lineages within plants, invertebrates, and vertebrates. Extremely tough structures can function much like armor, battering rams, or reinforcements that enhance the ability of organisms to win competitions, find mates, acquire food, escape predation, and withstand high winds or turbulent flow. From an engineering perspective, biological solutions are intriguing because they must work in a multifunctional context. An organism rarely can be optimally designed for only one function or one environmental condition. Some of these natural systems have developed well-orchestrated strategies, exemplified in the biological tissues of numerous animal and plant species, to synthesize and construct materials from a limited selection of available starting materials. The resulting structures display multiscale architectures with incredible fidelity and often exhibit properties that are similar, and frequently superior, to mechanical properties exhibited by many engineered materials. These biological systems have accomplished this feat through the demonstrated ability to tune size, morphology, crystallinity, phase, and orientation of minerals under benign processing conditions (i.e., near-neutral pH, room temperature, etc.) by establishing controlled synthesis and hierarchical 3D assembly of nano- to microscaled building blocks. These systems utilize organic-inorganic interactions and carefully controlled microenvironments that enable kinetic control during the synthesis of inorganic structures. This controlled synthesis and assembly requires orchestration of mineral transport and nucleation. The underlying organic framework, often consisting of polysaccharides and polypeptides, in these composites is critical in the spatial and temporal regulation of these processes. In fact, the organic framework is used not only to provide transport networks for mineral precursors to nucleation sites but also to precisely guide the formation and phase development of minerals and significantly improve the mechanical performance of otherwise brittle materials.Over the past 15 years, we have focused on a few of these extreme performing organisms, (Wang , Adv. Funct. Mater. 2013, 23, 2908; Weaver , Science 2012, 336, 1275; Huang , Nat. Mater. 2020, 19, 1236; Rivera , Nature 2020, 586, 543) investigating not only their ultrastructural features and mechanical properties but in some cases, how these assembled structures are mineralized. In specific instances, comparative analyses of multiscale structures have pinpointed which design principles have arisen convergently; when more than one evolutionary path arrives at the same solution, we have a good indication that it is the best solution. This is required for survival under extreme conditions. Indeed, we have found that there are specific architectural features that provide an advantage toward survival by enabling the ability to feed effectively or to survive against predatory attacks. In this Account, we describe 3 specific design features, nanorods, helicoids, and nanoparticles, as well as the interfaces in fiber-reinforced biological composites. We not only highlight their roles in the specific organisms but also describe how controlled syntheses and hierarchical assembly using organic (i.e., often chitinous) scaffolds lead to these integrated macroscale structures. Beyond this, we provide insight into multifunctionality: how nature leverages these existing structures to potentially add an additional dimension toward their utility and describe their translation to biomimetic materials used for engineering applications.

A non-lethal method to assess element content in the endangered Pinna nobilis.

The fan shell Pinna nobilis is the largest bivalve endemic to the Mediterranean and is actually a strongly endangered species. Due to the biological, ecological, and historical relevance of this species, the research of a non-lethal method to relate the element content in organism's tissues and environment can provide information potentially useful to evaluate environmental pollution and organism physiological status. In this study, a screening on element concentration in the animal growing environment (seawater and sediments) and in four soft tissues (hepatopancreas, gills, mantle, and muscle), and two acellular tissues (calcite shell layer, and byssus) was performed. The comparison among these results was used to assess whether the no-lethal acellular tissue element concentration can be used to reveal the element presence in the environment and soft tissues. Elements, such as B, Ag, As, Mn, Mo, Pb, or Se, showed a possible relationship between their presence in the byssus and soft tissues. In the byssus Cr, Sb, Sn, and V have shown to be mostly related to the environment, more than the soft tissues, and might be used to draw a historical record of the exposure of the organism. The element concentration in the calcite shell layer did not relate with environmental element concentrations. Essential elements, like Cu, Fe, Ni, and Zn, were present in calcite shell layer and byssus and are likely related to their biological activity in the organism. The research also gave an overview on the presence of pollution and on the preferential intake route of the element. In summary, this study, performed on a limited number of specimens of this protected species, indicated that element concentration in the byssus can be applied as non-lethal method to monitor this endangered species and its interaction with the elements in the growing environment.

Green Biocompatible Method for the Synthesis of Collagen/Chitin Composites to Study Their Composition and Assembly Influence on Fibroblasts Growth.

A green biocompatible route for the deposition and simultaneous assembly, by pH increment, of collagen/chitin composites was proposed. Both assembled and unassembled samples with different collagen/chitin ratios were synthesized, maintaining the ß-chitin polymorph. The first set showed a microfibrous organization with compositional submicron homogeneity. The second set presented a nanohomogeneous composition based on collagen nanoaggregates and chitin nanofibrils. The sets were tested as scaffolds for fibroblast growth (NIH-3T3) to study the influence of composition and assembly. In the unassembled scaffolds, the positive influence of collagen on cell growth mostly worn out in 48 h, while the addition of chitin enhanced this effect for over 72 h. The assembled samples showed higher viability at 24 h but a less positive effect on viability along the time. This work highlighted critical aspects of the influence that composition and assembly has on fibroblast growth, a knowledge worth exploiting in scaffold design and preparation.

Morphology and organization of the internal shell of Ariolimax californicus (Gastropoda; Stylommatophora), an asymmetric two-face biomineralized matrix.

A slug is a shell-less terrestrial gastropod mollusk. During evolution, slugs have lost their mineralized external shell but some of them have retained an internal shell (IS). Unlike external shells, which have been widely investigated, the ISs have been poorly studied. We report for the first time the compositional and complete morphological characterization of Ariolimax californicus' IS. According to literature, this shell calcifies and decalcifies depending on the animal's needs. Its composition is mostly organic, consisting of proteins and ß-chitin. The internal shell is organized in layers and membranes in which CaCO3 crystal formation occurs in specific areas. In the two faces of the IS we observed different morphologies and aggregations of calcite bio-crystals along with a different organization of the organic matrix. Dorsally, the mineral forms a thick layer composed of misaligned crystal aggregates of large dimensions, separated by thin organic layers. This suggests a protective purpose and the use of this layer as a long-term calcium storage system. Ventrally, the mineral phase is organized in small crystal aggregates of comparable size, separated by thin organic layers, and quite aligned one to the other. The whole ventral mineral layer is covered by a membrane, identified as the hypostracum. This face is proposed to be a short-term calcium storage system. In vitro crystallization experiments suggest massive calcium ions sequestration from the solution for the precipitation of calcite crystals inside the organic matrix. In conclusion, this research provides new information on the dynamic of biomineralization on mollusk evolved in calcium-poor environments.

Climate variation during the Holocene influenced the skeletal properties of Chamelea gallina shells in the North Adriatic Sea (Italy).

Understanding how marine taxa will respond to near-future climate changes is one of the main challenges for management of coastal ecosystem services. Ecological studies that investigate relationships between the environment and shell properties of commercially important marine species are commonly restricted to latitudinal gradients or small-scale laboratory experiments. This paper aimed to explore the variations in shell features and growth of the edible bivalve Chamelea gallina from the Holocene sedimentary succession to present-day thanatocoenosis of the Po Plain-Adriatic Sea system (Italy). Comparing the Holocene sub-fossil record to modern thanatocoenoses allowed obtaining an insight of shell variations dynamics on a millennial temporal scale. Five shoreface-related assemblages rich in C. gallina were considered: two from the Middle Holocene, when regional sea surface temperatures were higher than today, representing a possible analogue for the near-future global warming, one from the Late Holocene and two from the present-day. We investigated shell biometry and skeletal properties in relation to the valve length of C. gallina. Juveniles were found to be more porous than adults in all horizons. This suggested that C. gallina promoted an accelerated shell accretion with a higher porosity and lower density at the expense of mechanically fragile shells. A positive correlation between sea surface temperature and both micro-density and bulk density were found, with modern specimens being less dense, likely due to lower aragonite saturation state at lower temperature, which could ultimately increase the energetic costs of shell formation. Since no variation was observed in shell CaCO3 polymorphism (100% aragonite) or in compositional parameters among the analyzed horizons, the observed dynamics in skeletal parameters are likely not driven by a diagenetic recrystallization of the shell mineral phase. This study contributes to understand the response of C. gallina to climate-driven environmental shifts and offers insights for assessing anthropogenic impacts on this economic relevant species.

Influence of proteins on mechanical properties of a natural chitin-protein composite.

In many biogenic materials, chitin chains are assembled in fibrils that are wrapped by a protein fold. In them, the mechanical properties are supposed to be related to intra- and inter- interactions among chitin and proteins. This hypothesis has been poorly investigated. Here, this research theme is studied using the pen of Loligo vulgaris as a model material of chitin-protein composites. Chemical treatments were used to change the interactions involving only the proteic phase, through unfolding and/or degradation processes. Successively, structural and mechanical parameters were examined using spectroscopy, microscopy, X-ray diffractometry, and tensile tests. The data analysis showed that chemical treatments did not modify the structure of the chitin matrix. This allowed to derive from the mechanical test analysis the following conclusions: (i) the maximum stress (σmax) relies on the presence of the disulfide bonds; (ii) the Young's modulus (E) relies on the overall correct folding of the proteins; (iii) the whole removal of proteins induces a decrease of E (> 90%) and σmax (> 80%), and an increase in the maximum elongation. These observations indicate that in the chitin matrix the proteins act as a strengthener, which efficacy is controlled by the presence of disulfide bridges. This reinforcement links the chitin fibrils avoiding them to slide one on the other and maximizing their resistance and stiffness. In conclusion, this knowledge can explain the physio-chemical properties of other biogenic polymeric composites and inspire the design of new materials. STATEMENT OF SIGNIFICANCE: To date, no study has addressed on how proteins influence chitin-composite material's mechanical properties. Here we show that the Young's modulus and the maximum stress mainly rely on protein disulfide bonds, the inter-proteins ones and those controlling the folding of chitin-binding domains. The removal of protein matrix induce a reduction of Young's modulus and maximum stress, leaving the chitin matrix structurally unaltered. The measure of the maximum elongation shows that the chitin fibrils slide on each other only after removing the protein matrix. In conclusion, this research shows that the proteins act as a stiff matrix reinforced by di-sulfide bridges that link crystalline chitin fibrils avoiding them to slide one on the other.

Hierarchical chitinous matrices byssus-inspired with mechanical properties tunable by Fe(III) and oxidation.

In this study the multi-scale hierarchical structure of the ß-chitin matrix from squid pen of Loligo vulgaris was used as substrate to synthesize new bio-inspired materials. Aiming to mimic the byssus peculiar mechanical properties, we chemically functionalized the ß-chitin matrix with catechols, one of the main functional groups of the byssus. The obtained matrix preserved its multi-scale structural organization and was able to chelate reversibly Fe(III). Thus, it behaved as the byssus, acting as a metal cross-linkable matrix that upon metalation increased its Young's modulus, E (>10 times). The functionalized matrix was also cross-linked by oxidation provoking an increase of the E (>10 times) and first failure stress (>5 times). The oxidation of the functionalized matrix followed by metalation slightly increased the material mechanical properties. In conclusion, we added specific bio-functionalities in a natural matrix tuning its mechanical properties without altering its multi-scale organization.

Metal ion removal using waste byssus from aquaculture.

Byssus is a thread-like seafood waste that has a natural high efficiency in anchoring many metal ions thanks to its richness of diverse functional groups. It also has structural stability in extreme chemical, physical and mechanical conditions. The combination of these properties, absent in other waste materials, has novelty suggested its use as matrix for water remediation. Thus, pristine byssus, upon de-metalation, was studied to remove metal ions from ideal solutions at pH 4 and 7, as model chemical systems of industrial and environmental polluted waters, respectively. The byssus matrix's uptake of metal ions was determined by ICP-OES and its surface microstructure investigated by SEM. The results showed that the byssus matrix excellently uptakes metal ions slightly reorganizing its surface micro-structure. As example of its efficiency: 50 mg of byssus absorbed 21.7 mg·g-1 of Cd2+ from a 10 mM solution at pH 7. The adsorption isotherm models of Freundlich and Langmuir were mainly used to describe the system at pH 7 and pH 4, respectively. In conclusion, we showed that the byssus, a waste material that is an environmental issue, has the potential to purify polluted industrial and environmental waters from metal ions.

Cholesterol derivatives make large part of the lipids from epidermal molts of the desert-adapted Gila monster lizard (Heloderma suspectum).

In order to understand the cutaneous water loss in the desert-adapted and venomous lizard Heloderma suspectum, the microscopic structure and lipid composition of epidermal molts have been examined using microscopic, spectroscopic and chemical analysis techniques. The molt is formed by a variably thick, superficial beta-layer, an extensive mesos-region and few alpha-cells in its lowermost layers. The beta-layer contains most corneous beta proteins while the mesos-region is much richer in lipids. The proteins in the mesos-region are more unstructured than those located in the beta-layer. Most interestingly, among other lipids, high contents of cholesteryl-ß-glucoside and cholesteryl sulfate were detected, molecules absent or present in traces in other species of squamates. These cholesterol derivatives may be involved in the stabilization and compaction of the mesos-region, but present a limited permeability to water movements. The modest resistance to cutaneous water-loss of this species is compensated by adopting other physiological strategies to limit thermal damage and water transpiration as previous eco-physiological studies have indicated. The increase of steroid derivatives may also be implicated in the heat shock response, influencing the relative behavior in this desert-adapted lizard.

Structural characterization of the buccal mass of Ariolimax californicus (Gastropoda; Stylommatophora).

Biological materials such as chiton tooth, squid beak, and byssal threads of bivalves have inspired the development of new technologies. To this end, we have characterized the acellular components in the buccal mass of the terrestrial slug Ariolimax californicus (banana slug). These components are the radula, the jaw, and the odontophore. In the radula, calcium-rich denticles are tightly interlocked one to the other on top of a nanofibrous chitin membrane. The jaw has a nanostructured morphology made of chitin to achieve compression resistance and is directly linked to the foregut cuticle, which has a protective nanofibrous structure. Finally, in the odontophore, we observed a structurally elastic microstructure that interfaces soft tissues with a highly stressed radula membrane. Based on those observations, we discuss the interaction between these components and highlight how the materials in these task-specific components have evolved. This structure-properties-function study of the A. californicus' buccal mass may aid in the design and fabrication of novel bioinspired materials.

ß-Chitin Nanofibril Self-Assembly in Aqueous Environments.

Chitin is one of the most studied biopolymers but the understanding of how it assembles from molecules to microfibers is still limited. Organisms are able to assemble chitin with precise control over polymorphism, texture, and final morphology. The produced hierarchical structure leads to materials with outstanding mechanical properties. In this study, the self-assembly in aqueous solutions of ß-chitin nanofibrils, as far as possible similar to their native state, is investigated. These nanofibrils increase their tendency to self-assemble in fibers, up to millimetric length and ≈10 µm thickness, with the pH increasing from 3 to 8, forming loosely organized bundles as observed using cryo-transmission electron microscopy. The knowledge from this study contributes to the understanding of the self-assembly process that follows chitin once extruded from cells in living organisms. Moreover, it describes a model system which can be used to investigate how other biomolecules can affect the self-assembly of chitin nanofibrils.

ß-Chitin samples with similar microfibril arrangement change mechanical properties varying the degree of acetylation.

Chitin is widespread in nature and is increasingly used in synthetic process for the production of new biomaterials. Chitin degree of acetylation, crystalline structure and microfibril arrangement differentiate chemical, physical and mechanical properties. Nevertheless, no information are available on the relationship between the mechanical properties and the degree of acetylation (DA) in chitin samples in which the microfibril arrangement does not change. Here, samples of ß-chitin with decreasing DA, up to chitosan, were prepared using the squid pen of Loligo vulgaris. These samples were characterized by CP-MAS NMR spectroscopy, scanning electron microscopy, thermal analyses, synchrotron X-ray fiber diffraction and tensile tests. The results showed a similar microfibril arrangement decreasing the DA, except for the chitosan sample. The mechanical properties showed an increase of the maximum strain and a reduction of the maximum stress and Young's modulus, decreasing the DA. These changes, not linear with the DA, were related to structural changes at molecular structure level. The knowledge deriving from this study is of interest both for the understanding of the mechanical properties of chitinous biological samples, but also for the design and synthesis of new biomacromolecular materials.

Functional Biocompatible Matrices from Mussel Byssus Waste.

The mussel byssus is a biorenewable, protein-based material produced by marine mussels, which has attracted the interest of material scientists because of its remarkable mechanical and self-healing properties. Large quantities of byssus waste material from mussel mariculture are produced every year, which have great potential as a raw starting material for producing sustainable advanced materials. In this work, we developed a facile and scalable method to synthesize whole byssus-based porous matrices that retain part of the hierarchical organization of the pristine material at the nanoscale. The resulting material is biocompatible and maintains important native byssus features: metal ion chelation (≥12 mg/g), collagen domains, and hierarchical organization, with tunable properties controlled via metal ion content. Furthermore, these biocompatible matrices showed a dye absorbing efficiency (up to 64 mg/g for anionic dyes) that was similar to or higher than that of the pristine byssus, a proof of preservation of structural motifs. These findings indicate that biorenewable matrices originating from byssus waste could have potential use in biomedical engineering and applied material science.

Supramolecular Anion Recognition Mediates One-Pot Synthesis of 3-Amino-[1,2,4]-triazolo Pyridines from Thiosemicarbazides.

A facile one-pot synthesis of 3-amino-[1,2,4]-triazolo[4,3-a]pyridines from thiosemicarbazides through anion mediated synthesis is reported. Thiosemicarbazides derived from 2-hydrazino pyridine, 5-chloro 2-hydrazino pyridine, and 2-hydrazine quinoline were formed in situ as anion receptors in the presence of TBAF. Under microwave heating, thiosemicarbazides furnished the triazolo pyridines in good to moderate yields. The formation of the thiosemicarbazides hydrogen bonding anion receptors was critical in cascading the reaction toward the formation of the triazolo pyridines.