Sustainable keratin-based packaging film incorporating phenolated lignin nanoparticles with photothermal antibacterial and antioxidant properties

The preservation of fresh foods remains a critical challenge due to oxidative spoilage and microbial contamination, highlighting the demand for sustainable packaging materials with integrated antioxidant and antimicrobial functionalities. Conventional plastic packaging, while widely used, not only lacks these essential functions but also poses severe environmental burdens, prompting the search for eco-friendly alternatives. In this study, a fully bio-based keratin/carboxymethyl cellulose hydrogel film (PLKC) was developed, incorporating phenolic-modified lignin nanoparticles (PL NPs) as a green photothermal agent to achieve excellent photothermal antimicrobial and antioxidant properties, to be used as packaging film. The PLKC film exhibits outstanding mechanical properties based on networks formed by disulfide bonds and hydrogen bonds, with tensile strength and elongation at break reaching 12.4 MPa and 48.3%, respectively. And the self-adhesive capabilities of the film enable tight sealing upon simple pressing. Benefiting from the excellent light absorption of PL NPs, the PLKC film displays rapid photothermal response, reaching temperatures above 50 ℃ within 30 s under xenon lamp irradiation. This photothermal effect synergistically enhances the inherent antibacterial efficacy of PL NPs, resulting in inhibition rates exceeding 95% against both S. aureus and E. coli, alongside a high radical scavenging activity. These combined functionalities were verified by packaging fresh strawberries, of which the shelf life was effectively prolonged. The PLKC film presents a sustainable solution to simultaneously address food waste and plastic pollution, holding significant potential for application in food packaging.