Waste valorization by methacrylation of fish skin collagen for bioprinting of neural stem cells

This study developed a sustainable collagen methacryloyl bioink from grouper fish skin waste and evaluated its suitability for DLP-based neural biofabrication. Collagen was extracted from fish skin through alkaline pretreatment, bleaching, acetic acid solubilization, pepsin digestion, salt precipitation, dialysis, and lyophilization, yielding high-purity pepsin-soluble collagen. The extracted collagen was chemically modified with methacrylic anhydride to produce low- and high-methacrylation ColMA formulations. Circular dichroism and SDS-PAGE confirmed preservation of collagen structural features, while FTIR and 1H NMR verified successful methacrylation. Rheological testing showed rapid UV-induced gelation, and high ColMA exhibited higher complex viscosity and stronger crosslinking behaviour than low ColMA. SEM, swelling, degradation, and UniVert compression testing showed that high ColMA formed a denser, more mechanically stable hydrogel, while low ColMA swelled more and degraded more rapidly. High ColMA was then used for DLP printing of complex shapes with high shape fidelity and for NSC-laden constructs that maintained cell viability above 85% through 14 days. Complementary hMSC neurogenic differentiation studies showed neurite-like morphology and upregulation of neuronal markers TUBB3 and NEFH. Overall, the study demonstrates that fish skin waste can be converted into a low-cost, sustainable, photocrosslinkable ColMA platform for 3D bioprinting and neural tissue engineering applications.