Antibacterial photodynamic inactivation of pH-responsive microspheres based on chitosan/carboxymethyl chitosan with hypericin and its application in food preservation

New antibacterial materials play an important role in preventing food safety caused by pathogen contamination. In this study, a pH-responsive nanoparticle was developed by incorporating hypericin (HY) into a chitosan/carboxymethyl chitosan carrier (CS/CMC@HY). CS/CMC@HY had excellent pH-responsive release performance (85.3%), photodynamic performance and surface charge. Depending on the antibacterial properties of polysaccharides and the photodynamic therapy (PDT) activity of HY, CS/CMC@HY showed excellent synergistic antibacterial effect on Staphylococcus aureus ( S. aureus ) and Escherichia coli ( E. coli ), and its performance was proportional to the material concentration and light time. The minimum inhibitory concentration of Staphylococcus aureus was 100 mg/mL. Then, the actual sample test showed that CS/CMC@HY could effectively prevent the bacterial infection of green grapes, and the weight loss rate decreased to 6.04% and 9.03% within 10 days, indicating that the material had excellent application prospects in the field of food antibacterial and preservation.