Valorization of sea urchins waste for the development of composite biomaterials for regenerative medicine

Sea urchins possess peculiar anatomic/physiological adaptations in terms of specialized connective tissues (e.g. the Mutable Collagenous Tissues, MCT) and antioxidant compounds which can be exploited for biomedical applications through an eco-friendly approach. Indeed, the food waste deriving from processing of edible sea urchins (up to 90% of their mass) can still be a source of 1) MCT-derived native collagen, extracted from the peristomial membrane, which can be used to produce biomimetic collagen-made biomaterials, 2) polyhydroxynaphtoquinones (PHNQ) a class of polyphenolic with potent antioxidant properties that can be obtained by the test and the spines. By combining these molecules, we recently optimized a protocol to develop polyphenol-rich and collagen-based composite biomaterials for regenerative medicine applications, which retain both biomimetic and bioactive properties. In order to verify the suitability of the produced sea urchin-derived matrices for tissue regeneration purposes, in the present work, the composites were characterized in terms of ultrastructure (SEM), degradation kinetics (physiological and enzymatic conditions), swelling properties, water uptake, release kinetics of PHNQ and antioxidant activity (ABTS assay). Results showed that composites are ultrastructurally similar to the pure collagen-based counterpart, displaying an homogeneous porous structure without visible aggregates. Degradation kinetics and swelling test showed a significant improvement of the stability in the composites, compared to both simple collagen-based and UV-crosslinked biomaterials. Lastly, PHNQ remained absorbed to the collagen matrix where they fully retained their antioxidant activity, thus providing the biomaterial with a further functionality potentially useful in tissue repair. In conclusion, these findings show that 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 produce customized and green devices of marine origin.