From sea urchins waste to tissue regeneration: innovative collagen-based biocomposite materials

Sea urchins are considered as a food delicacy in many countries of the world. Particularly, gonads are the only edible part of these animals, while the rest (about 70-90%) is discarded thus producing a large amount of waste. The majority of sea urchins on the market comes from natural stocks, this resulting in species overexploitation. In a circular economy perspective, we recently showed that valorisation strategies of sea urchin wastes can be developed towards high-added value products for the production of innovative collagen-based biomaterials useful for biomedical applications. Particularly, from this waste we successfully extracted fibrillar collagen1,2 (extracted from the peristomial membrane) and polyhydroxynaphtoquinones (extracted from the test and spines), a class of polyphenolic antioxidant pigments with a potent free-radical scavenging activity3. Subsequently, we combined both collagen and antioxidants to produce composite biomaterials, with biomimetic and bioactive features. Composite biomaterials were characterized in terms of morphology, degradation kinetics, release kinetics of the antioxidants and antioxidant activity. As results, SEM analyses showed that biocomposites have a porous meshwork-like structure, similar to the simple collagen-based counterpart. Degradation kinetics in both physiological and enzymatic conditions indicated a significant better stability of the composites, compared to the simple collagen-based biomaterials. In addition, in physiological conditions, the degradation kinetics was similar to a commercial bovine collagen membrane used as reference (Integra®). Furthermore, using UPLC and ABTS assay, we demonstrated that antioxidants remained adsorbed into the collagen matrix, maintaining their antioxidant power. Overall, these findings show how sea urchins waste can be fully exploited to extract valuable molecules and develop innovative and multifunctional biomaterials, useful for tissue regeneration. As a future perspective, 3D bioprinting technology is under development to improve the mechanical-strucutral properties of this green biomaterials.