Preparation of safe and highly photothermal antibacterial passion fruit peel extract/polydopamine nanoparticles to be incorporated into HPMC films for food packaging.

The eradication of foodborne pathogenic bacteria is very important in the context of contemporary food preservation techniques. This study reports the preparation of a photothermal antibacterial material and its application in strawberry packaging. The passion fruit peel extract/polydopamine (PFPE/PDA) nanoparticles were synthesised using the catechol moiety of polyphenols from PFPE with the amino moiety in dopamine (DA) in a Schiff base reaction or Michael addition reaction. Results showed that the PFPE/PDA nanoparticles exhibited strong photothermal conversion efficiency (41.79%) and antibacterial rates of over 99% for Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) under near-infrared (NIR) light irradiation. The material was found to be safe through cytotoxicity experiments. The incorporation of PFPE/PDA into a hydroxypropylmethylcellulose (HPMC) base film demonstrated the bacterial survival rate of E. coli was only 21.33% ± 0.73%, while that of S. aureus was merely 7.71% ± 0.16% under NIR light irradiation. This effectively extends the shelf life of strawberries, thereby highlighting the excellent freshness preservation ability of the film. Excellent photothermal properties offer new solutions for film applications in antibacterial food packaging.