Synergistic reinforcement of carboxymethyl cellulose film with deep eutectic extract and polydopamine@nanolignin from spent coffee grounds: Enhanced antioxidant and photothermal antibacterial activity for active food packaging.

The persistence of petroleum-based plastic packaging poses escalating risks to ecology and human wellness, underscoring the critical need of green food-packaging alternatives. Herein, sustainable active carboxymethyl cellulose (CMC)-based composite films were developed by incorporating a deep eutectic extract (DE) and polydopamine-modified nanolignin (PL), both derived from coffee grounds waste (CGW). DE functioned as a green plasticizer and a source of antioxidant phytochemicals, while PL served as an antioxidant and photothermal nanofiller. Their synergistic interactions reinforced intermolecular bonding, yielding a compact microstructure with enhanced physicochemical properties. Notably, CMC/DE/PL5% film exhibited 138.33% increase in tensile strength, 58.06% reduction in water vapor permeability, and 99.52% UV shielding. The film showed strong antioxidant activity (2.24 μmol TE/g film for DPPH; 1.32 μmol TE/g film for ABTS), 100% antibacterial efficacy against S. aureus and E. coli under 808 nm NIR irradiation, while maintaining favorable biosafety and biodegradability. Packaging tests demonstrated effective preservation of blueberry quality, extending shelf life to 15 days at room temperature under NIR irradiation. This work provides a high-value utilization pathway for biomass waste and a scalable strategy for developing sustainable active packaging aligned with circular bioeconomy principles.