Antimicrobial photodynamic coating on glass surfaces for food preservation

Food preservation plays a vital role in achieving sustainable development goals, ensuring food security, reducing food waste, and promoting health and economic stability. As global populations continue to grow and environmental challenges persist, the importance of effective food preservation methods will only increase. In particular, glass surfaces contribute significantly to food preservation by maintaining food quality, ensuring safety, and enhancing shelf life through their inert, impermeable, and hygienic properties. In this work, glass surfaces (GSs) were covalently coated with photosensitizers (GS-PS) to eliminate microbial contamination through the photodynamic inactivation of microorganisms (PDI). Thus, 5,10,15,20-tetrakis(pentafluorophenyl)-2,3-[methane(N-methyl)iminomethane]chlorine (TPCF₂₀) and its metal complex with Zn(II) (ZnTPCF₂₀) were used as photodynamic agents. Morphological studies of GS-PS revealed a uniform distribution of the PS on the surfaces. The contact angles indicated an increase in the lipophilicity of the surfaces coated with the PS. The absorption and emission spectra of the GS-PS surfaces exhibited the characteristic bands of the corresponding monomers in solution. Photodynamic studies revealed that the GS-PS surfaces were capable of generating singlet molecular oxygen. The photoinactivation efficacy of these surfaces was assessed against Staphylococcus aureus. Bacterial cells on GS-PS surfaces were eradicated (over 6 log, >99.9999% reduction in survival) after 45 min of white light irradiation. Furthermore, the potential for sustainable use through recycling was evaluated after a round of PDI treatments. These surfaces were also effective in photoinactivating individual bacteria of S. aureus attached to the GS-PS. Therefore, the GS-PS materials exhibited suitable properties to eliminate microbial contamination and maintain aseptic conditions for food preservation.