Fabrication and characterization of bio-composite films from gelatin capsule waste reinforced with biosynthesized zinc oxide nanoparticles from Cha-Kram leaf extract

• Gelatin capsule waste was converted into biodegradable biopolymer films • Biosynthesized ZnONPs from Cha-Kram leaf extract exhibit biological activity • Biosynthesized ZnONPs addition enhanced film properties • Bio-nanocomposite films are categorized as a novel type of active films • Bio-nanocomposite films fully biodegrade within 15 days in soil Biopolymer-based films present a sustainable alternative to conventional plastics; however, their practical use is often limited by poor material properties. This study investigated the biosynthesis of zinc oxide nanoparticles (ZnONPs) using Cha-Kram ( Suaeda maritima (L.) Dumort) leaf extract and their incorporation (0-2% w/v) into biopolymer films derived from gelatin capsule waste to enhance material performance. The structural and chemical properties of the synthesized ZnONPs were confirmed using UV–Vis spectroscopy, while field-emission transmission electron microscopy analysis revealed a rod-like morphology with particle sizes ranging from 20 to 300 nm. The ZnONPs displayed strong antibacterial activity, with inhibition zones of 1.11-2.66 mm against both Gram-positive, Gram-negative bacteria and antioxidant activity of 43.5% DPPH radical scavenging activity. In film applications, the ZnONPs enhanced thickness from 0.254 to 0.332 mm, tensile strength from 3.72 to 6.32 MPa, and thermal stability, while also contributing to more opaqueness. Additionally, their incorporation imparted antioxidant and antibacterial properties, effectively inhibiting both Gram-positive and Gram-negative bacteria. Fourier Transform Infrared Spectroscopy showed peak shifts and pattern changes, confirming the interactions between proteins and the ZnONPs. Notably, the ZnONPs infused films underwent complete degradation within 15 days under soil burial conditions. These findings demonstrated the potential of ZnONPs films for active packaging and the feasibility of using gelatin capsule waste for sustainable, biodegradable film production.