Valorization of Fish Scale Waste Into Composite Films: Physicochemical, Mechanical, Antibacterial, and HET-CAM Angiogenesis Evaluation.

Chitosan extracted from Labeo rohita fish scales via chemical demineralization, deproteinization, and deacetylation yields 25% overall from raw scales. The chitosan has 88%-90% deacetylation, a molecular weight (MW) of 109.5 kDa, and low residual ash (0.1%) and protein (0.29%). Composite films (CGP) with fixed gelatin: polyvinylpyrrolidone (PVP, 10:5) and varying chitosan (1%-7% w/v) are prepared. FTIR confirms cross‑linking; SEM shows smooth surfaces for CGP 3% and CGP 5%, but rougher texture for CGP 7%. Water uptake decreases with higher chitosan content (160% for CGP 1% vs. 22% for CGP 7%). PBS buffer uptake is highest for CGP 1%-5% (80%-120%), and lowest for CGP 7% (∼40%). Lower chitosan content slows degradation. Tensile strength increases with chitosan concentration (27 MPa for CGP 1% to 32.8 MPa for CGP 7%), while elongation at break decreases (13% to 4%). Antibacterial activity against Escherichia coli and Staphylococcus aureus is strongest for CGP 3% and CGP 5% (inhibition zones 13-14 mm), outperforming pure chitosan. In the hen's egg test on the chorioallantoic membrane (HET‑CAM) assay, CGP 3% induces the highest angiogenic response (27.2 ± 0.3 vs. 12.9 ± 0.6 vessels in control), with no toxicity. CGP 3% and CGP 5% are optimal for wound‑healing applications.