Intelligent and sustainable food packaging utilizing quaternary ammonium chitosan with porphyrin structure for...

The amphiphilic and photodynamically responsive porphyrin grafted O-quaternary ammonium chitosan (QTPCS) was synthesized using O-quaternized chitosan as a precursor, incorporating a porphyrin structure. Oregano essential oil (OEO) was encapsulated within QTPCS to create drug-loaded micelles (QTPCS@OEO), facilitating the slow release of the OEO. Utilizing the acid-producing characteristics associated with food spoilage, carbon quantum dots (CQDs) responsive to pH changes were synthesized, which enhanced the singlet oxygen (¹O₂) generation efficiency of QTPCS through a fluorescence resonance energy transfer mechanism. Subsequently, gelatin was utilized as the substrate, and QTPCS@OEO along with CQDs were incorporated to fabricate an intelligent packaging film (CQD + QT@OEO) capable of continuous antibacterial drug release and real-time monitoring through a casting film formation method. The tensile strength of the resultant CQD + QT@OEO film reached 8.5 MPa, and its antioxidant activity and ultraviolet light blocking capability was enhanced compared to those of gelatin film. Furthermore, the sustained release of OEO was extended to 140 h. When applied to strawberry preservation, this composite film effectively prolonged the shelf life of strawberries to 12 days. Cytotoxicity assays indicated that the CQD + QT@OEO film exhibited negligible cytotoxicity and demonstrated excellent biocompatibility. These experimental findings suggest that the developed CQD + QT@OEO film holds significant promise for applications in intelligent and sustainable food packaging.