Many cosmetic formulations have collagen as a major component because of its significant benefits as a natural humectant and moisturizer. This industry is constantly looking for innovative, sustainable, and truly efficacious products, so marine collagen based formulations are arising as promising alternatives. A solid description and characterization of this protein is fundamental to guarantee the highest quality of each batch. In the present study, we present an extensive characterization of marine-derived collagen extracted from salmon and codfish skins, targeting its inclusion as component in cosmetic formulations. Chemical and physical characterizations were performed using several techniques such as sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), Fourier Transformation Infrared (FTIR) spectroscopy rheology, circular dichroism, X-ray diffraction, humidity uptake, and a biological assessment of the extracts regarding their irritant potential. The results showed an isolation of type I collagen with high purity but with some structural and chemical differences between sources. Collagen demonstrated a good capacity to retain water, thus being suitable for dermal applications as a moisturizer. A topical exposure of collagen in a human reconstructed dermis, as well as the analysis of molecular markers for irritation and inflammation, exhibited no irritant potential. Thus, the isolation of collagen from fish skins for inclusion in dermocosmetic applications may constitute a sustainable and low-cost platform for the biotechnological valorization of fish by-products.

Atlantic cod is processed industrially for food purposes, with several by-products being directed to animal feed and other ends. Looking particularly into swim bladders, the extraction of collagen can be a valuable strategy for by-product valorization, explored in the present work for the first time. Collagen was extracted using acetic acid (ASCsb) and pepsin (PSCsb) with yields of 5.72% (w/w) and 11.14% (w/w), respectively. SDS-PAGE profile showed that the extracts were compatible with type I collagen. FTIR, CD and XRD results suggest that the PSCsb structure underwent partial denaturation, with microDSC showing a band at 54 °C probably corresponding to a melting process, while ASCsb structure remained intact, with preserved triple helix and a denaturation temperature of 29.6 °C. Amino acid composition indicates that the total content of proline-like amino acids was 148/1000 residues for ASCsb and 141/1000 residues for PSCsb, with a hydroxylation degree of about 37%. The extracts exhibited a typical shear thinning behavior, interesting property regarding their further processing toward the development of biomaterials. In this regard, assessment of metabolic activity of human fibroblast cells cultured in the presence of collagen extracts with concentrations up to 3 mg/mL revealed the absence of cytotoxic behavior. Collagen extracts obtained from Atlantic cod swim bladders shown attractive properties regarding their use in cosmetic or biomedical applications.

With the worldwide increase of fisheries, fish wastes have had a similar increase, alternatively they can be seen as a source of novel substances for the improvement of society’s wellbeing. Elasmobranchs are a subclass fished in high amounts, with some species being mainly bycatch. They possess an endoskeleton composed mainly by cartilage, from which chondroitin sulfate is currently obtained. Their use as a viable source for extraction of type II collagen has been hypothesized with the envisaging of a biomedical application, namely in biomaterials production. In the present work, raw cartilage from shark (Prionace glauca) and ray (Zeachara chilensis and Bathyraja brachyurops) was obtained from a fish processing company and submitted to acidic and enzymatic extractions, to produce acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). From all the extractions, P. glauca PSC had the highest yield (3.5%), followed by ray ASC (0.92%), ray PSC (0.50%), and P. glauca ASC (0.15%). All the extracts showed similar properties, with the SDS-PAGE profiles being compatible with the presence of both type I and type II collagens. Moreover, the collagen extracts exhibited the competence to maintain their conformation at human basal temperature, presenting a denaturation temperature higher than 37 °C. Hydrogels were produced using P. glauca PSC combined with shark chondroitin sulfate, with the objective of mimicking the human cartilage extracellular matrix. These hydrogels were cohesive and structurally-stable at 37 °C, with rheological measurements exhibiting a conformation of an elastic solid when submitted to shear strain with a frequency up to 4 Hz. This work revealed a sustainable strategy for the valorization of fisheries’ by-products, within the concept of a circular economy, consisting of the use of P. glauca, Z. chilensis, and B. brachyurops cartilage for the extraction of collagen, which would be further employed in the development of hydrogels as a proof of concept of its biotechnological potential, ultimately envisaging its use in marine biomaterials to regenerate damaged cartilaginous tissues.