Penaeus monodon shell waste-derived chitosan nanoparticles show biocompatibility and broad antimicrobial activity.

Crustacean shell waste, a mostly untapped marine byproduct, presents considerable environmental risks while also offering a rich but underutilized source of biopolymers. Although chitosan nanoparticles (ChNPs) have received attention for their bioactivity and biocompatibility, most research focuses on commercial chitosan, ignoring local waste valorization, complete nanoparticle characterisation, and cross-disciplinary applications. To bridge these gaps, the current work presents an integrated, sustainable methodology to convert Penaeus monodon shell waste into bio-functional chitosan nanoparticles by green ionic gelation. Physicochemical investigations (FESEM, TEM, FTIR, XRD, TGA, and DLS) revealed crystallinity, thermal stability, and consistent nanoscale shape of the molecule. The ChNPs showed better antibacterial efficiency against fish pathogens and antioxidant activity (DPPH and H2O2). Additionally, cytotoxicity screening on NIH 3T3 fibroblast cells supported their high biocompatibility. Notably, a new chitosan-carboxymethyl cellulose (CMC) hydrogel composite was developed and evaluated as a natural covering for post-harvest fruit preservation. While these findings are promising, more focus on antimicrobial studies, multi-cell line and in vivo biosafety validation, optimization of hydrogel formulation and large-scale trials should be done in future. This work establishes a circular economy model linking waste management, nanotechnology, and biological efficacy on a single platform, bridging research gaps and opening new pathways for sustainable applications.