Design of chitosan/PVA biopolymer films enhanced cobalt-doped zinc oxide nanoparticles for green antibacterial packaging

This study presents the successful preparation of cobalt-doped zinc oxide incorporated chitosan (CS)–polyvinyl alcohol (PVA) nanocomposite films using a simple casting method for green antibacterial packaging application. Systematically investigates Co2+ ion integration into the ZnO lattice within CS–PVA matrix to enhance antibacterial activity, with optimization performed using response surface methodology–central composite design (RSM–CCD), which constitutes the novelty of this work. Structural and morphological analyses (XRD, FTIR, SEM, EDX, TEM, UV-DRS, TGA) confirmed successful Co-doped ZnO on the surface of the CS–PVA film with a mean diameter of 27 nm. The optimal PVA/CS and Co/ZnO composition by RSM-CCD exhibited maximum inhibition zones of 14 mm and 16 mm against Staphylococcus aureus and Escherichia coli, respectively. Increasing Co doping enhanced its antibacterial properties, as evidenced by the reduction in the band gap energy, increased thermal stability and contact angle, and mechanical properties. Whereas, the water vapor permeability rate, solubility, and moisture retention decreased, indicating suitability for food packaging applications. The maximum release of Zn2+ ions in 10% ethanol and 3.0% acetic acid simulants was 14.63 and 16.65 mg, respectively, both below the EFSA limit of 25 mg/person/day. These findings demonstrate that CS–PVA/Co-doped ZnO films offer a promising, environmentally friendly approach for bioactive packaging, contributing to food safety and public health.