Abstract

Photodynamic decontamination using chlorophyllin is often limited by photosensitizer leaching, surface staining, poor reusability, and inconsistent antimicrobial performance. To address these challenges, a food-compatible chlorophyllin– Ca3(PO4)2 nanohybrid was synthesized and optimized to improve chlorophyllin immobilization and photodynamic efficacy. Encapsulation efficiency increased with calcium ion concentration and incubation time, reaching approximately 99% under optimized synthesis conditions despite the absence of highly ordered nanoflower architectures. Upon visible-light irradiation, the nanohybrid exhibited potent antibacterial activity against Salmonella typhimurium, achieving approximately 98% bacterial reduction. Additional studies demonstrated effective photodynamic inactivation (PDI) of gram-positive bacteria, including Staphylococcus aureus and Bacillus subtilis, confirming broad-spectrum antimicrobial activity. Reactive oxygen species scavenger assays identified singlet oxygen as the primary antimicrobial species responsible for bacterial inactivation, while fluorescence staining, scanning electron microscopy analysis, and intracellular leakage studies confirmed extensive membrane disruption. The nanohybrid also achieved approximately 98% PDI of naturally occurring microbial populations recovered from fresh-cut cucumber, cabbage, and spinach surfaces. Unlike free chlorophyllin, the immobilized nanohybrid showed negligible chlorophyllin release, no visible surface staining, and retained substantial antibacterial activity over multiple reuse cycles. Collectively, these findings demonstrate that chlorophyllin–Ca3(PO4)2 nanohybrid provides a reusable, non-migrating, and consumer-compatible photodynamic platform for enhancing the microbial safety of fresh-cut produce.

Key words: Fresh-cut produce; Salmonella Typhimurium; Chlorophyllin-Ca₃(PO₄)₂ nanohybrid; Photodynamic decontamination; Food safety