Search

Sea urchin spines are biogenic single crystals of magnesium calcite that are stiff, strong, damage tolerant and light and have a bicontinuous porous structure. Here, we showed that the removal of their intraskeletal organic matrix materials did not affect the compressive mechanical properties and generated an open porosity. This matrix was able to adsorb and release oxytetracycline, a broad-spectrum antibiotic. The drug-loaded sea urchin matrix induced bacterial cell death after 4 and 8 hours of incubation of both Gram-negative E. coli and Gram-positive S. aureus strains and this process induces an inhibition of bacterial cell adhesion. In conclusion, this study shows that thermally treated sea urchin spines are a compressive resistant and lightweight matrix able to load drugs and with potential use in spine fusion, a challenging application that requires withstanding high compressive loading.

Bacterial keratitis (BK) is a severe eye infection commonly associated with Staphylococcus aureus (S. aureus), posing a significant risk to vision, especially among contact lens wearers. This research introduces a novel smart nanoplatform (deMS@cNF), developed from demineralized mussel shells (deMS) and reinforced with chitin (CT) nanofibrils, specifically designed for portable photothermal disinfection of contact lenses. The nanoplatform leverages the photothermal properties of eumelanin in mussel shells (MS), which, when activated by a simple bike flashlight, rapidly heats to temperatures up to 95 °C, effectively destroying bacterial contamination. In vitro tests demonstrate that the nanoplatform is biocompatible and non-toxic, making it suitable for medical applications. This study highlights an innovative approach to converting marine biowaste into a safe, effective, and low-cost portable method for disinfecting contact lenses, showcasing the potential of the deMS@cNF platform for broader antimicrobial applications., (© 2024 Wiley‐VCH GmbH.)

We report the gelation propensity of three gelators derived from l-dihydroxyphenylalanine (l-Dopa), where the amino group is derivatized with three different fatty acids (lauric acid, palmitic acid, and azelaic acid). The long aliphatic side chains should introduce additional van der Waals interactions among the molecules, contributing to the self-assembly process. The hydrogels have been prepared with the pH change method, and both the hydrogels and the corresponding aerogels have been analyzed using several techniques. In any case, Lau-Dopa provides stronger hydrogels compared with the other gelators. This property may be ascribed to its tendency to efficiently form supramolecular β-sheet structures, as outlined by the ECD, IR, and SEM analyses. Moreover, the preliminary measurement of the apparent p K a displays for Lau-Dopa two plateaux, as previously observed for, one at about pH 12 and a second one at pH 7.5. Thus, its p K a results in two apparent p K a shifts of ∼8.5 and ∼4 pH units above the theoretical p K a , as a consequence of a multistep self-assembly pathway that correlates, in the final β-sheet-based hydrogel, with a high degree of order and stability.

Alcohol dehydrogenases (ADHs) are a group of zinc-binding enzymes belonging to the medium-length dehydrogenase/reductase (MDR) protein superfamily. In plants, these enzymes fulfill important functions involving the reduction of toxic aldehydes to the corresponding alcohols (as well as catalyzing the reverse reaction, i.e., alcohol oxidation; ADH1) and the reduction of nitrosoglutathione (GSNO; ADH2/GSNOR). We investigated and compared the structural and biochemical properties of ADH1 and GSNOR from Arabidopsis thaliana. We expressed and purified ADH1 and GSNOR and determined two new structures, NADH-ADH1 and apo-GSNOR, thus completing the structural landscape of Arabidopsis ADHs in both apo- and holo-forms. A structural comparison of these Arabidopsis ADHs revealed a high sequence conservation (59% identity) and a similar fold. In contrast, a striking dissimilarity was observed in the catalytic cavity supporting substrate specificity and accommodation. Consistently, ADH1 and GSNOR showed strict specificity for their substrates (ethanol and GSNO, respectively), although both enzymes had the ability to oxidize long-chain alcohols, with ADH1 performing better than GSNOR. Both enzymes contain a high number of cysteines (12 and 15 out of 379 residues for ADH1 and GSNOR, respectively) and showed a significant and similar responsivity to thiol-oxidizing agents, indicating that redox modifications may constitute a mechanism for controlling enzyme activity under both optimal growth and stress conditions., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

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 β-chitin fibrils (β-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 β-chitOx 1 wt.% at pH 9, inducing the gelation by sonication. These hydrogels were exposed to different environments, such as different amounts of Ca 2+ , Na + or Mg 2+ 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.

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., Competing Interests: The authors declare no competing financial interest., (© 2024 The Authors. Published by American Chemical Society.)

Calcium phosphates are widely studied in orthopedics and dentistry, to obtain biomimetic and antibacterial implants. However, the multi-substituted composition of mineralized tissues is not fully reproducible from synthetic procedures. Here, for the first time, we investigate the possible use of a natural, fluorapatite-based material, i.e. , Lingula anatina seashell, resembling the composition of bone and enamel, as a biomaterial source for orthopedics and dentistry. Indeed, thanks to its unique mineralization process and conditions, L. anatina seashell is among the few natural apatite-based shells, and naturally contains ions having possible antibacterial efficacy, i.e. , fluorine and zinc. After characterization, we explore its deposition by ionized jet deposition (IJD), to obtain nanostructured coatings for implantable devices. For the first time, we demonstrate that L. anatina seashells have strong antibacterial properties. Indeed, they significantly inhibit planktonic growth and cell adhesion of both Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli . The two strains show different susceptibility to the mineral and organic parts of the seashells, the first being more susceptible to zinc and fluorine in the mineral part, and the second to the organic (chitin-based) component. Upon deposition by IJD, all films exhibit a nanostructured morphology and sub-micrometric thickness. The multi-doped, complex composition of the target is maintained in the coating, demonstrating the feasibility of deposition of coatings starting from biogenic precursors (seashells). In conclusion, Lingula seashell-based coatings are non-cytotoxic with strong antimicrobial capability, especially against Gram-positive strains, consistently with their higher susceptibility to fluorine and zinc. Importantly, these properties are improved compared to synthetic fluorapatite, showing that the films are promising for antimicrobial applications.

Among the main phenomena that are causing significant changes in ocean waters are warming and acidification, largely due to anthropogenic activities. Growing evidence suggests that climate change is having more substantial and rapid effects on marine communities than on terrestrial ones, triggering several physiological responses in these organisms, including in corals. Here we investigated, for first time in the field, the combined effect of increasing seawater acidification and warming on tissue regeneration rate of three Mediterranean scleractinian coral species characterized by different trophic strategies and growth modes. Balanophyllia europaea (solitary, zooxanthellate), Leptopsammia pruvoti (solitary, non-zooxanthellate) and Astroides calycularis (colonial, non-zooxanthellate) specimens were transplanted, during a cold, intermediate, and warm period, along a natural pH gradient generated by an underwater volcanic crater at Panarea Island (Mediterranean Sea, Italy), characterized by continuous and localized CO 2 emissions at ambient temperature. Our results show a decrease in regenerative capacity, especially in the zooxanthellate species, with increasing seawater temperature and acidification, with demonstrated species-specific differences. This finding suggests that increasing seawater temperature and acidification could have a compounding effect on coral regeneration following injury, potentially hindering the capacity of corals to recover following physical disturbance under predicted climate change., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Zvy Dubinsky reports financial support was provided by Bar-Ilan University., (Copyright © 2023. Published by Elsevier B.V.)

Nanocrystalline calcium carbonate (CaCO 3 ) and amorphous CaCO 3 (ACC) are materials of increasing technological interest. Nowadays, they are mainly synthetically produced by wet reactions using CaCO 3 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 CaCO 3 (bCC) from waste mollusk seashells into nanocrystalline CaCO 3 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 CaCO 3 (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 CaCO 3 and ACC composites or mixtures having species-specific features. These materials can enlarge the already wide fields of applications of CaCO 3 , which span from medical to material science., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

We have developed a straightforward, one-pot, low-temperature hydrothermal method to transform oyster shell waste particles (bCCP) from the species Crassostrea gigas (Mg-calcite, 5 wt% Mg) into hydroxyapatite (HA) micro/nanoparticles. The influence of the P reagents (H 3 PO 4 , KH 2 PO 4 , and K 2 HPO 4 ), P/bCCP molar ratios (0.24, 0.6, and 0.96), digestion temperatures (25-200 °C), and digestion times (1 week-2 months) on the transformation process was thoroughly investigated. At 1 week, the minimum temperature to yield the full transformation significantly reduced from 160 °C to 120 °C when using K 2 HPO 4 instead of KH 2 PO 4 at a P/bCCP ratio of 0.6, and even to 80 °C at a P/bCCP ratio of 0.96. The transformation took place via a dissolution-reprecipitation mechanism driven by the favorable balance between HA precipitation and bCCP dissolution, due to the lower solubility product of HA than that of calcite at any of the tested temperatures. Both the bCCP and the derived HA particles were cytocompatible for MG-63 human osteosarcoma cells and m17.ASC murine mesenchymal stem cells, and additionally, they promoted the osteogenic differentiation of m17.ASC, especially the HA particles. Because of their physicochemical features and biological compatibility, both particles could be useful osteoinductive platforms for translational applications in bone tissue engineering.

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., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Fragrances are volatile organic compounds widely used in our daily life. Unfortunately, the high volatility required to reach human receptors reduces their persistency in the air. To contrast this effect, several strategies may be used. Among them, we present here the combination of two techniques: the microencapsulation in supramolecular gels and the use of profragrances. We report a study on the controlled lactonization of four esters derived from o -coumaric acid. The ester lactonization spontaneously occurs after exposure to solar light, releasing coumarin and the corresponding alcohol. To determine the rate of fragrance release, we compared the reaction in solution and in a supramolecular gel and we demonstrated that the lactonization reaction always occurs slower in the gel. We also studied the more suitable gel for this aim, by comparing the properties of two supramolecular gels obtained with the gelator Boc-L-DOPA(Bn) 2 -OH in a 1:1 ethanol/water mixture in different gelator concentration (0.2% and 1% w / v ). The gel prepared with 1% w/v gelator concentration is stronger and less transparent than the other and was used for the profragrances encapsulation. In any case, we obtained a significative reduction of lactonization reaction in gel, compared with the same reaction in solution.

Ocean acidification caused by shifts in ocean carbonate chemistry resulting from increased atmospheric CO 2 concentrations is threatening many calcifying organisms, including corals. Here we assessed autotrophy vs heterotrophy shifts in the Mediterranean zooxanthellate scleractinian coral Balanophyllia europaea acclimatized to low pH/high pCO 2 conditions at a CO 2 vent off Panarea Island (Italy). Dinoflagellate endosymbiont densities were higher at lowest pH Sites where changes in the distribution of distinct haplotypes of a host-specific symbiont species, Philozoon balanophyllum, were observed. An increase in symbiont C/N ratios was observed at low pH, likely as a result of increased C fixation by higher symbiont cell densities. δ 13 C values of the symbionts and host tissue reached similar values at the lowest pH Site, suggesting an increased influence of autotrophy with increasing acidification. Host tissue δ 15 N values of 0‰ strongly suggest that diazotroph N 2 fixation is occurring within the coral tissue/mucus at the low pH Sites, likely explaining the decrease in host tissue C/N ratios with acidification. Overall, our findings show an acclimatization of this coral-dinoflagellate mutualism through trophic adjustment and symbiont haplotype differences with increasing acidification, highlighting that some corals are capable of acclimatizing to ocean acidification predicted under end-of-century scenarios., (© 2023. The Author(s).)

Control over the shape and morphology of single crystals is a theme of great interest in fundamental science and for technological application. Many synthetic strategies to achieve this goal are inspired by biomineralization processes. Indeed, organisms are able to produce crystals with high fidelity in shape and morphology utilizing macromolecules that act as modifiers. An alternative strategy can be the recovery of crystals from biomineralization products, in this case, seashells. In particular, waste mussel shells from aquaculture are considered. They are mainly built up of single crystals of calcite fibers and aragonite tablets forming an outer and an inner layer, respectively. A simple mechanochemical treatment has been developed to separate and recover these two typologies of single crystals. The characterization of these single crystals showed peculiar properties with respect to the calcium carbonate from quarry or synthesis. We exploited these biomaterials in the water remediation field using them as substrate adsorbing dyes. We found that these substrates show a high capability of adsorption for anionic dye, such as Eosin Y, but a low capability of adsorption for cationic dyes, such as Blue Methylene. The adsorption was reversible at pH 5.6. This application represents just an example of the potential use of these biogenic single crystals. We also envision potential applications as reinforcing fillers and optical devices., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Oxygenic phototrophs perform carbon fixation through the Calvin-Benson cycle. Different mechanisms adjust the cycle and the light-harvesting reactions to rapid environmental changes. Photosynthetic glyceraldehyde 3-phosphate dehydrogenase (GAPDH) is a key enzyme in the cycle. In land plants, different photosynthetic GAPDHs exist: the most abundant isoform is formed by A 2 B 2 heterotetramers and the least abundant by A 4 homotetramers. Regardless of the subunit composition, GAPDH is the major consumer of photosynthetic NADPH and its activity is strictly regulated. While A 4 -GAPDH is regulated by CP12, AB-GAPDH is autonomously regulated through the C-terminal extension (CTE) of its B subunits. Reversible inhibition of AB-GAPDH occurs via the oxidation of a cysteine pair located in the CTE and the substitution of NADP(H) with NAD(H) in the cofactor-binding site. These combined conditions lead to a change in the oligomerization state and enzyme inhibition. SEC-SAXS and single-particle cryo-EM analysis were applied to reveal the structural basis of this regulatory mechanism. Both approaches revealed that spinach (A 2 B 2 ) n -GAPDH oligomers with n = 1, 2, 4 and 5 co-exist in a dynamic system. B subunits mediate the contacts between adjacent tetramers in A 4 B 4 and A 8 B 8 oligomers. The CTE of each B subunit penetrates into the active site of a B subunit of the adjacent tetramer, which in turn moves its CTE in the opposite direction, effectively preventing the binding of the substrate 1,3-bisphosphoglycerate in the B subunits. The whole mechanism is made possible, and eventually controlled, by pyridine nucleotides. In fact, NAD(H), by removing NADP(H) from A subunits, allows the entrance of the CTE into the active site of the B subunit, hence stabilizing inhibited oligomers.

Stony corals (order: Scleractinia) differ in growth form and structure. While stony corals have gained the ability to form their aragonite skeleton once in their evolution, the suite of proteins involved in skeletogenesis is different for different coral species. This led to the conclusion that the organic portion of their skeleton can undergo rapid evolutionary changes by independently evolving new biomineralization-related proteins. Here, we used liquid chromatography-tandem mass spectrometry to sequence skeletogenic proteins extracted from the encrusting temperate coral Oculina patagonica. We compare it to the previously published skeletal proteome of the branching subtropical corals Stylophora pistillata as both are regarded as highly resilient to environmental changes. We further characterized the skeletal organic matrix (OM) composition of both taxa and tested their effects on the mineral formation using a series of overgrowth experiments on calcite seeds. We found that each species utilizes a different set of proteins containing different amino acid compositions and achieve a different morphology modification capacity on calcite overgrowth. Our results further support the hypothesis that the different coral taxa utilize a species-specific protein set comprised of independent gene co-option to construct their own unique organic matrix framework. While the protein set differs between species, the specific predicted roles of the whole set appear to underline similar functional roles. They include assisting in forming the extracellular matrix, nucleation of the mineral and cell signaling. Nevertheless, the different composition might be the reason for the varying organization of the mineral growth in the presence of a particular skeletal OM, ultimately forming their distinct morphologies., (© 2022. The Author(s).)

Calcium carbonate (CaCO 3 ) is an important inorganic mineral in biological and geological systems. Traditionally, it is widely used in plastics, papermaking, ink, building materials, textiles, cosmetics, and food. Over the last decade, there has been rapid development in the controlled synthesis and surface modification of CaCO 3 , the stabilization of amorphous CaCO 3 (ACC), and CaCO 3 -based nanostructured materials. In this review, the controlled synthesis of CaCO 3 is first examined, including Ca 2+ -CO 3 2- systems, solid-liquid-gas carbonation, water-in-oil reverse emulsions, and biomineralization. Advancing insights into the nucleation and crystallization of CaCO 3 have led to the development of efficient routes towards the controlled synthesis of CaCO 3 with specific sizes, morphologies, and polymorphs. Recently-developed surface modification methods of CaCO 3 include organic and inorganic modifications, as well as intensified surface reactions. The resultant CaCO 3 can then be further engineered via template-induced biomineralization and layer-by-layer assembly into porous, hollow, or core-shell organic-inorganic nanocomposites. The introduction of CaCO 3 into nanostructured materials has led to a significant improvement in the mechanical, optical, magnetic, and catalytic properties of such materials, with the resultant CaCO 3 -based nanostructured materials showing great potential for use in biomaterials and biomedicine, environmental remediation, and energy production and storage. The influences that the preparation conditions and additives have on ACC preparation and stabilization are also discussed. Studies indicate that ACC can be used to construct environmentally-friendly hybrid films, supramolecular hydrogels, and drug vehicles. Finally, the existing challenges and future directions of the controlled synthesis and functionalization of CaCO 3 and its expanding applications are highlighted.

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 β-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 β-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.

S-nitrosylation is a redox post-translational modification widely recognized to play an important role in cellular signaling as it can modulate protein function and conformation. At the physiological level, nitrosoglutathione (GSNO) is considered the major physiological NO-releasing compound due to its ability to transfer the NO moiety to protein thiols but the structural determinants regulating its redox specificity are not fully elucidated. In this study, we employed photosynthetic glyceraldehyde-3-phosphate dehydrogenase from Chlamydomonas reinhardtii (CrGAPA) to investigate the molecular mechanisms underlying GSNO-dependent thiol oxidation. We first observed that GSNO causes reversible enzyme inhibition by inducing S-nitrosylation. While the cofactor NADP + partially protects the enzyme from GSNO-mediated S-nitrosylation, protein inhibition is not observed in the presence of the substrate 1,3-bisphosphoglycerate, indicating that the S-nitrosylation of the catalytic Cys149 is responsible for CrGAPA inactivation. The crystal structures of CrGAPA in complex with NADP + and NAD + reveal a general structural similarity with other photosynthetic GAPDH. Starting from the 3D structure, we carried out molecular dynamics simulations to identify the protein residues involved in GSNO binding. The reaction mechanism of GSNO with CrGAPA Cys149 was investigated by quantum mechanical/molecular mechanical calculations, which permitted to disclose the relative contribution of protein residues in modulating the activation barrier of the trans-nitrosylation reaction. Based on our findings, we provide functional and structural insights into the response of CrGAPA to GSNO-dependent regulation, possibly expanding the mechanistic features to other protein cysteines susceptible to be oxidatively modified by GSNO., (Copyright © 2022 The Authors. Published by Elsevier B.V. All rights reserved.)

Biomaterials such as seashells are intriguing due to their remarkable properties, including their hierarchical structure from the nanometer to the micro- or even macroscopic scale. Transferring this nanostructure to generate nanostructured polymers can improve their electrical conductivity. Here, we present the synthesis of polypyrrole using waste seashell powder as a template to prepare a polypyrrole/CaCO 3 composite material. Various synthesis parameters were optimized to produce a composite material with an electrical conductivity of 2.1 × 10 -4 ± 3.2 × 10 -5 S/cm. This work presents the transformation of waste seashells into sustainable, electronically conductive materials and their application as an antistatic agent in polymers. The requirements of an antistatic material were met for a safety shoe sole.

Otolith biomineralization results from biochemical processes regulated by the interaction of internal (physiological) and external (environmental) factors which lead to morphological and ultrastructural variability at intra- and interspecific levels. The aim of this study was to conduct a multi-scale analysis of the sagittal otoliths of the Merlucius merlucius (European hake) from the western Adriatic Sea in order to correlate otolith features with fish ontogeny and sex. We show that otoliths of sexually undifferentiated (non-sexed) individuals having a fish body total length (TL) less than 15 cm had faster growth in length, width, area, perimeter, volume and weight and a higher amount of organic matrix compared with otoliths of sexually differentiated individuals (females and males) having a fish size range of 15-50 cm. Most importantly, with increasing fish TL, female saccular otoliths contained a higher number of protuberances and rougher surface compared with male specimens, which showed more uniform mean curvature density. The differences between females and males discovered in this study could be associated with fish hearing adaptation to reproductive behavioural strategies during the spawning season. The outcomes of this research provide insights on how size and sex-related variations in otolith features may be affected by fish ecological and behavioural patterns., Competing Interests: We declare we have no competing interests., (© 2022 The Authors.)

The three gelators presented in this work (Boc-D-Phe-L-Oxd-OH F0 , Boc-D-F 1 Phe-L-Oxd-OH F1 and Boc-D-F 2 Phe-L-Oxd-OH F2 ) share the same scaffold and differ in the number of fluorine atoms linked to the aromatic ring of phenylalanine. They have been applied to the preparation of gels in 0.5% or 1.0% w / v concentration, using three methodologies: solvent switch, pH change and calcium ions addition. The general trend is an increased tendency to form structured materials from F0 to F1 and F2 . This property ends up in the formation of stronger materials when fluorine atoms are present. Some samples, generally formed by F1 or F2 in 0.5% w / v concentration, show high transparency but low mechanical properties. Two gels, both containing fluorine atoms, show increased stiffness coupled with high transparency. The biocompatibility of the gelators was assessed exposing them to fibroblast cells and demonstrated that F1 and F2 are not toxic to cells even in high concentration, while F0 is not toxic to cells only in a low concentration. In conclusion, the presence of even only one fluorine atom improves all the gelators properties: the gelation ability of the compound, the rheological properties and the transparency of the final materials and the gelator biocompatibility.

The diversity in the skeletal features of coral species is an outcome of their evolution, distribution and habitat. Here, we explored, from macro- to nano-scale, the skeletal structural and compositional characteristics of three coral species belonging to the genus Balanophyllia having different trophic strategies. The goal is to address whether the onset of mixotrophy influenced the skeletal features of B. elegans, B. regia, and B. europaea. The macroscale data suggest that the presence of symbiotic algae in B. europaea can lead to a surplus of energy input that increases its growth rate and skeletal bulk density, leading to larger and denser corals compared to the azooxanthellate ones, B. regia and B. elegans. The symbiosis would also explain the higher intra-skeletal organic matrix (OM) content, which is constituted by macromolecules promoting the calcification, in B. europaea compared to the azooxanthellate species. The characterization of the soluble OM also revealed differences between B. europaea and the azooxanthellate species, which may be linked to diverse macromolecular machineries responsible for skeletal biosynthesis and final morphology. Differently, the crystallographic features were homogenous among species, suggesting that the basic building blocks of skeletons remained a conserved trait in these related species, regardless of the trophic strategy. These results show changes in skeletal phenotype that could be triggered by the onset of mixotrophy, as a consequence of the symbiotic association, displaying remarkable plasticity of coral skeletons which repeatedly allowed this coral group to adapt to a range of changing environments throughout its geological history., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier B.V. All rights reserved.)

Ocean acidification, due to the increase of carbon dioxide (CO 2 ) concentration in the atmosphere and its absorption by the oceans, affects many aspects of marine calcifying organisms' biology, including reproduction. Most of the available studies on low pH effects on coral reproduction have been conducted on tropical species under controlled conditions, while little information is reported for either tropical or temperate species in the field. This study describes the influence of decreasing pH on sexual reproduction of the temperate non-zooxanthellate colonial scleractinian Astroides calycularis , transplanted in four sites along a natural pH gradient at the underwater volcanic crater of Panarea Island (Tyrrhenian Sea, Italy). The average pH values of each site (range: pH TS 8.07-7.40) match different scenarios of the Intergovernmental Panel on Climate Change (IPCC) for the end of the century. After 3 months under experimental conditions, the reproductive parameters of both oocytes and spermaries (abundance, gonadal index, and diameters) seem to be unaffected by low pH. However, a delay in spermary development in the pre-fertilization period and a persistence of mature oocytes in the fertilization period were observed in the most acidic site. Furthermore, no embryos were found in colonies from the two most acidic sites, suggesting a delay or an interruption of the fertilization process due to acidified conditions. These findings suggest a negative effect of low pH on A. calycularis sexual reproduction. However, long-term experiments, including the synergistic impact of pH and temperature, are needed to predict if this species will be able to adapt to climate change over the next century., Competing Interests: None declared., (© 2021 The Authors. Limnology and Oceanography published by Wiley Periodicals LLC on behalf of Association for the Sciences of Limnology and Oceanography.)

This study investigates the effects of long-term exposure to OA on skeletal parameters of four tropical zooxanthellate corals naturally living at CO 2 seeps and adjacent control sites from two locations (Dobu and Upa Upasina) in the Papua New Guinea underwater volcanic vent system. The seeps are characterized by seawater pH values ranging from 8.0 to about 7.7. The skeletal porosity of Galaxea fascicularis, Acropora millepora, massive Porites, and Pocillopora damicornis was higher (up to ~ 40%, depending on the species) at the seep sites compared to the control sites. Pocillopora damicornis also showed a decrease of micro-density (up to ~ 7%). Thus, further investigations conducted on this species showed an increase of the volume fraction of the larger pores (up to ~ 7%), a decrease of the intraskeletal organic matrix content (up to ~ 15%), and an increase of the intraskeletal water content (up to ~ 59%) at the seep sites. The organic matrix related strain and crystallite size did not vary between seep and control sites. This multi-species study showed a common phenotypic response among different zooxanthellate corals subjected to the same environmental pressures, leading to the development of a more porous skeletal phenotype under OA., (© 2021. The Author(s).)

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., (© 2021. The Author(s).)

The function-optimized properties of biominerals arise from the hierarchical organization of primary building blocks. Alteration of properties in response to environmental stresses generally involves time-intensive processes of resorption and reprecipitation of mineral in the underlying organic scaffold. Here, we report that the load-bearing shells of the brachiopod Discinisca tenuis are an exception to this process. These shells can dynamically modulate their mechanical properties in response to a change in environment, switching from hard and stiff when dry to malleable when hydrated within minutes. Using ptychographic X-ray tomography, electron microscopy and spectroscopy, we describe their hierarchical structure and composition as a function of hydration to understand the structural motifs that generate this adaptability. Key is a complementary set of structural modifications, starting with the swelling of an organic matrix on the micron level via nanocrystal reorganization and ending in an intercalation process on the molecular level in response to hydration., (© 2021. The Author(s).)

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 β-chitin. The internal shell is organized in layers and membranes in which CaCO 3 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., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Photochemical activation is proposed as a general method for controlling the crystallization of sparingly soluble carbonates in space and time. The photogeneration of carbonate in an alkaline environment is achieved upon photo-decarboxylation of an organic precursor by using a conventional 365 nm UV LED. Local irradiation was conducted focusing the LED light on a 300 μm radius spot on a closed glass crystallization cell. The precursor solution was optimized to avoid the precipitation of the photoreaction organic byproducts and prevent photo-induced pH changes to achieve the formation of calcium carbonate only in the corresponding irradiated area. The crystallization was monitored in real-time by time-lapse imaging. The method is also shown to work in gels. Similarly, it was also shown to photo-activate locally the formation of barium carbonate biomorphs. In the last case, the morphology of these biomimetic structures was tuned by changing the irradiation intensity., (© 2021 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.)

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 β-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.

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., Competing Interests: Authors have declared that no competing interests exist.

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 (σ max ) 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 σ max (> 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., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020. Published by Elsevier Ltd.)

Spherulites are radial distributions of acicular crystals, common in biogenic, geologic, and synthetic systems, yet exactly how spherulitic crystals nucleate and grow is still poorly understood. To investigate these processes in more detail, we chose scleractinian corals as a model system, because they are well known to form their skeletons from aragonite (CaCO 3 ) spherulites, and because a comparative study of crystal structures across coral species has not been performed previously. We observed that all 12 diverse coral species analyzed here exhibit plumose spherulites in their skeletons, with well-defined centers of calcification (CoCs), and crystalline fibers radiating from them. In 7 of the 12 species, we observed a skeletal structural motif not observed previously: randomly oriented, equant crystals, which we termed "sprinkles". In Acropora pharaonis, these sprinkles are localized at the CoCs, while in 6 other species, sprinkles are either layered at the growth front (GF) of the spherulites, or randomly distributed. At the nano- and micro-scale, coral skeletons fill space as much as single crystals of aragonite. Based on these observations, we tentatively propose a spherulite formation mechanism in which growth front nucleation (GFN) of randomly oriented sprinkles, competition for space, and coarsening produce spherulites, rather than the previously assumed slightly misoriented nucleations termed "non-crystallographic branching". Phase-field simulations support this mechanism, and, using a minimal set of thermodynamic parameters, are able to reproduce all of the microstructural variation observed experimentally in all of the investigated coral skeletons. Beyond coral skeletons, other spherulitic systems, from aspirin to semicrystalline polymers and chocolate, may also form according to the mechanism for spherulite formation proposed here. STATEMENT OF SIGNIFICANCE: Understanding the fundamental mechanisms of spherulite nucleation and growth has broad ranging applications in the fields of metallurgy, polymers, food science, and pharmaceutical production. Using the skeletons of reef-building corals as a model system for investigating these processes, we propose a new spherulite growth mechanism that can not only explain the micro-structural diversity observed in distantly related coral species, but may point to a universal growth mechanism in a wide range of biologically and technologically relevant spherulitic materials systems., (Copyright © 2020. Published by Elsevier Ltd.)

In this study the multi-scale hierarchical structure of the β-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 β-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., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

Protein S-nitrosylation plays a fundamental role in cell signaling and nitrosoglutathione (GSNO) is considered as the main nitrosylating signaling molecule. Enzymatic systems controlling GSNO homeostasis are thus crucial to indirectly control the formation of protein S-nitrosothiols. GSNO reductase (GSNOR) is the key enzyme controlling GSNO levels by catalyzing its degradation in the presence of NADH. Here, we found that protein extracts from the microalga Chlamydomonas reinhardtii catabolize GSNO via two enzymatic systems having specific reliance on NADPH or NADH and different biochemical features. Scoring the Chlamydomonas genome for orthologs of known plant GSNORs, we found two genes encoding for putative and almost identical GSNOR isoenzymes. One of the two, here named CrGSNOR1, was heterologously expressed and purified. Its kinetic properties were determined and the three-dimensional structures of the apo-, NAD + - and NAD + /GSNO-forms were solved. These analyses revealed that CrGSNOR1 has a strict specificity towards GSNO and NADH, and a conserved folding with respect to other plant GSNORs. The catalytic zinc ion, however, showed an unexpected variability of the coordination environment. Furthermore, we evaluated the catalytic response of CrGSNOR1 to thermal denaturation, thiol-modifying agents and oxidative modifications as well as the reactivity and position of accessible cysteines. Despite being a cysteine-rich protein, CrGSNOR1 contains only two solvent-exposed/reactive cysteines. Oxidizing and nitrosylating treatments have null or limited effects on CrGSNOR1 activity and folding, highlighting a certain resistance of the algal enzyme to redox modifications. The molecular mechanisms and structural features underlying the response to thiol-based modifications are discussed., (Copyright © 2020. Published by Elsevier B.V.)

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 Cd 2+ 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.

Carbohydrates, along with proteins and peptides, are known to represent a major class of biomacromolecules involved in calcium carbonate biomineralization. However, in spite of multiple physical and biochemical characterizations, the explicit role of saccharide macromolecules (long chains of carbohydrate molecules) in mineral deposition is not yet understood. In this study, we investigated the influence of two common acidic monosaccharides (MSs), the two simplest forms of acidic carbohydrates, namely glucuronic and galacturonic acids, on the formation of calcite crystals in vitro. We show here that the size, morphology, and microstructure of calcite crystals are altered when they are grown in the presence of these MSs. More importantly, these MSs were found to become incorporated into the calcite crystalline lattice and induce anisotropic lattice distortions, a phenomenon widely studied for other biomolecules related to CaCO 3 biomineralization, but never before reported in the case of single MSs. Changes in the calcite lattice induced by MSs incorporation were precisely determined by high-resolution synchrotron powder X-ray diffraction. We believe that the results of this research may deepen our understanding of the interaction of saccharide polymers with an inorganic host and shed light on the implications of carbohydrates for biomineralization processes., (© 2020 Wiley‐VCH GmbH.)

Bionic composites are an emerging class of materials produced exploiting living organisms as reactors to include synthetic functional materials in their native and highly performing structures. In this work, single wall carboxylated carbon nanotubes (SWCNT-COOH) were incorporated within the roots of living plants of Arabidopsis thaliana . This biogenic synthetic route produced a bionic composite material made of root components and SWCNT-COOH. The synthesis was possible exploiting the transport processes existing in the plant roots. Scanning electrochemical microscopy (SECM) measurements showed that SWCNT-COOH entered the vascular bundles of A. thaliana roots localizing within xylem vessels. SWCNT-COOH preserved their electrical properties when embedded inside the root matrix, both at a microscopic level and a macroscopic level, and did not significantly affect the mechanical properties of A. thaliana roots., (Copyright © 2020 Magnabosco, Pantano, Rapino, Di Giosia, Valle, Taxis, Sparla, Falini, Pugno and Calvaresi.)

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-β-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.

Biotemplating makes it possible to prepare materials with complex structures by taking advantage of nature's ability to generate unique morphologies. In this work, we designed and produced a multi-scale porosity (MSP) scaffold starting from sea urchin spines by adding an additional nano-porosity to its native micro-porosity. The final replica shows porosity in both length scales and is an effective high-performing photocatalytic material.

The native structure of the β-chitin in the gladius (squid pen) of Loligo vulgaris squid can be used as a natural plaster to entrap and release a model drug, doxorubicin, in a targeted and controlled way. Local pH determines the protonation state of the doxorubicin molecules, controlling the two phenomena. Confocal microscopy shows that doxorubicin is uniformly embedded in the β-chitin squid pen and is not simply adsorbed on its surface. Coculture with HeLa cells reveals that the β-chitin squid pen plaster is perfectly biocompatible, while when it is loaded with doxorubicin it shows high cytotoxicity toward the cancer cells. The drug, once released, rapidly accumulates inside the cells. In conclusion, the native structure of a β-chitin squid pen can be potentially applied as a "green" pH-responsive drug vehicle for controlled release.

Corals and other biomineralizing organisms use proteins and other molecules to form different crystalline polymorphs and biomineral structures. In corals, it's been suggested that proteins such as Coral Acid Rich Proteins (CARPs) play a major role in the polymorph selection of their calcium carbonate (CaCO 3 ) aragonite exoskeleton. To date, four CARPs (1-4) have been characterized: each with a different amino acid composition and different temporal and spatial expression patterns during coral developmental stages. Interestingly, CARP3 is able to alter crystallization pathways in vitro, yet its function in this process remains enigmatic. To better understand the CARP3 function, we performed two independent in vitro CaCO 3 polymorph selection experiments using purified recombinant CARP3 at different concentrations and at low or zero Mg 2+ concentration. Our results show that, in the absence of Mg 2+ , CARP3 selects for the vaterite polymorph and inhibits calcite. However, in the presence of a low concentration of Mg 2+ and CARP3 both Mg-calcite and vaterite are formed, with the relative amount of Mg-calcite increasing with CARP3 concentration. In all conditions, CARP3 did not select for the aragonite polymorph, which is the polymorph associated to CARP3 in vivo, even in the presence of Mg 2+ (Mg:Ca molar ratio equal to 1). These results further emphasize the importance of Mg:Ca molar ratios similar to that in seawater (Mg:Ca equal to 5) and the activity of the biological system in a aragonite polymorph selection in coral skeleton formation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

Protein aggregation is a complex physiological process, primarily determined by stress-related factors revealing the hidden aggregation propensity of proteins that otherwise are fully soluble. Here we report a mechanism by which glycolytic glyceraldehyde-3-phosphate dehydrogenase of Arabidopsis thaliana (AtGAPC1) is primed to form insoluble aggregates by the glutathionylation of its catalytic cysteine (Cys149). Following a lag phase, glutathionylated AtGAPC1 initiates a self-aggregation process resulting in the formation of branched chains of globular particles made of partially misfolded and totally inactive proteins. GSH molecules within AtGAPC1 active sites are suggested to provide the initial destabilizing signal. The following removal of glutathione by the formation of an intramolecular disulfide bond between Cys149 and Cys153 reinforces the aggregation process. Physiological reductases, thioredoxins and glutaredoxins, could not dissolve AtGAPC1 aggregates but could efficiently contrast their growth. Besides acting as a protective mechanism against overoxidation, S-glutathionylation of AtGAPC1 triggers an unexpected aggregation pathway with completely different and still unexplored physiological implications., Competing Interests: The authors declare no competing interest.

Boc-L-DOPA(OBn) 2 -OH is a simple synthetic molecule that promotes hydrogelation through electrostatic and π-π stacking interactions. Hydrogelation can occur in alkaline conditions by the use of triggers. Four hydrogels were prepared varying the base, NaOH or Na 2 CO 3 , and the trigger, GdL or CaCl 2 . When the hydrogel formed in the presence of Na 2 CO 3 and CaCl 2 , the concomitant production of CaCO 3 crystals occurred, generating an organic/inorganic composite material. It was observed that the hydrogel once self-assembled preserved its status even if the trigger, the calcium ions, was removed. The viscoelastic behavior of the hydrogels was analyzed through rheological experiments, which showed a solid-like behavior of the hydrogels. The corresponding xerogels were analyzed mainly by scanning electron microscopy (SEM) and synchrotron X-ray diffraction analysis (XRD). They showed differences in structure, morphology, and fiber organization according to their source. This research presents a hydrogel system that can be applied as a soft biomaterial for tissue engineering, cosmetics, food, and environmental science. Moreover, it represents a model for biomineralization studies in which the hydrogel structure can act as an analogue of the insoluble matrix that confines the calcification site, provides Ca 2+ , and preserves its structure.

We investigate the photocatalytic performance of composites prepared in a one-step process by liquid-phase exfoliation of graphite in the presence of TiO 2 nanoparticles (NPs) at atmospheric pressure and in water, without heating or adding any surfactant, and starting from low-cost commercial reagents. These show enhanced photocatalytic activity, degrading up to 40% more pollutants with respect to the starting TiO 2 -NPs, in the case of a model dye target, and up to 70% more pollutants in the case of nitrogen oxides. In order to understand the photo-physical mechanisms underlying this enhancement, we investigate the photo-generation of reactive species (trapped holes and electrons) by ultrafast transient absorption spectroscopy. We observe an electron transfer process from TiO 2 to the graphite flakes within the first picoseconds of the relaxation dynamics, which causes the decrease of the charge recombination rate, and increases the efficiency of the reactive species photo-production.

The effect of Mg2+ on the precipitation pathway of CaCO3 in absolute ethanol has been studied to investigate the role of ion solvation in the crystallization process. Our data reveal that high concentrations of Mg2+ promote the precipitation of an amorphous transient phase together with non-stoichometric hydrated phases of calcium carbonate.

The controlled release of cell differentiating agents is crucial in many aspects of regenerative medicine. Here we propose the use of hybrid calcite single crystals as micro-carriers for the controlled and localized release of retinoic acid, which is entrapped within the crystalline lattice. The release of retinoic acid occurs only in the proximity of stem cells, upon dissolution of the calcite hybrid crystals that are dispersed in the fibrin scaffold. These hybrid crystals provide a sustained dosage of the entrapped agent. The environment provided by this composite scaffold enables differentiation towards neuronal cells that form a three-dimensional neuronal network.

The biomineralization of corals occurs under conditions of high and low supersaturation with respect to aragonite, which corresponds to day- or night-time periods of their growth, respectively. Here, in vitro precipitation of aragonite in artificial seawater was investigated at a high supersaturation, allowing spontaneous nucleation and growth, as well as at low supersaturation conditions, which allowed only the crystal growth on the deliberately introduced aragonite seeds. In either chemical systems, soluble organic matrix (SOM) extracted from Balanophyllia europaea (light sensitive) or Leptopsammia pruvoti (light insensitive) was added. The analyses of the kinetic and thermodynamic data of aragonite precipitation and microscopic observations showed that, at high supersaturation, the SOMs increased the induction time, did not affect the growth rate and were incorporated within aggregates of nanoparticles. At low supersaturation, the SOMs affected the aggregation of overgrowing crystalline units and did not substantially change the growth rate. On the basis of the obtained results we can infer that at high supersaturation conditions the formation of nanoparticles, which is typically observed in the skeleton's early mineralization zone may occur, whereas at low supersaturation the overgrowth on prismatic seeds observed in the skeleton fiber zone is a predominant process. In conclusion, this research brings insight on coral skeletogenesis bridging physicochemical (supersaturation) and biological (role of SOM) models of coral biomineralization and provides a source of inspiration for the precipitation of composite materials under different conditions of supersaturation., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

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., Competing Interests: The authors have declared that no competing interests exist.

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 β-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.