Functional Biocompatible Matrices from Mussel Byssus Waste

Sustainable 3D Scaffolds Based on β-Chitin and Collagen I for Wound Dressing Applications

The development of greener substitutes for plastics is gaining massive importance in today's society. This also involves the medical field, where disposable materials are used to grant sterility. Here, a novel protocol using only a water-based solvent for the preparation of bio-based composite foams of actual β-chitin and collagen type I is presented. The influence of the ratio of this chitin polymorph to the collagen on the final material is then studied. The samples with 50:50 and 75:25 ratios produce promising results, such as remarkable water absorption (up to 7000 wt.%), exposed surface (up to 7 m2·g-1), and total pore volume (over 80 vol.%). The materials are also tested using wet mechanical compression, exhibiting a Young's modulus and tenacity (both calculated between 2% and 25% of deformation) of up to 20 Pa and 9 kPa, respectively. Fibroblasts, keratinocytes, and osteoblasts are grown on these scaffolds. The viability of fibroblasts and keratinocytes is observed for 72 h, whereas the viability of osteoblasts is observed for up to 21 days. Under the two conditions mentioned, cell activity and adhesion work even better than under its counterpart condition of pure collagen. In conclusion, these materials are promising candidates for sustainable regenerative medicine scaffolds or, specifically, as biodegradable wound dressings.

Sustainable alternatives for by-products derived from industrial mussel processing: A critical review

The industrial mussel processing generates significant quantities of waste. Nearly 30% of one metric tonne of processed mussel is finally destined for human consumption. Regardless of the mussel commodities, an important quantity of waste is concentrated at several sub-processes, such as input reception, washing and declumping shells, and mussel meat extraction stages, or by means of the rejection of mussels only due to a size characteristic criterion established by the target market. Despite the main segregated waste comprising shells, byssus threads, residual meat and wastewater, a heterogeneous composition must be taken into account, since much of the solid waste is commonly gathered and compacted for landfill transportation purposes. This paper reviews the sustainable management strategies for mussel by-products, addressing their limitations for an industrial implementation to obtain value-added products. It is concluded that, although there is a well-known diversity of waste sustainable management alternatives, several proposed products (e.g., collagen, bio-adhesives, biopolymer, and adsorbent for pollutants) still remain in a potential framework, circumscribed into laboratory results, subject to an optimization process, to a validation by industrial pre-scale trials, or even limited by the associated production costs. Future researches should focus on reducing the uncertainties linked with their technical-economic feasibility for an industrial scale development.

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 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.

Elucidating the Biological Activity of Fish-Derived Collagen and Gelatine Hydrolysates using Animal Cell Culture - A Review

A large percentage of a fish's weight is generally discarded during fish processing. Reducing the waste products of marine origin is a subject of great interest within the scientific community. Pelagic byproducts, such as the structural protein collagen, which can be generated during the processing of fish, have been proposed as an alternative to terrestrial, mammalian sources due to advantages including high availability and low risk of zoonotic disease transmission. Gelatine has multiple possible applications, ranging from nutraceutical applications to cosmetics and has the advantage of being generally regarded as safe. In this multidisciplinary review, the chemistry of gelatine and its parent protein collagen, the chemical reactions to generate their hydrolysates, and studies on their biological activities using animal cell culture are discussed.

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 (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.

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.

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.