Chlorin-based photodynamic antimicrobial glass surfaces for the eradication of Staphylococcus aureus

The risk of infections from contaminated surfaces poses a significant threat to global public health. This study presents the development of antimicrobial coatings based on photodynamic inactivation (PDI) by covalently attaching 5,10,15,20-tetrakis(pentafluorophenyl)-2,3-[methane(N-methyl)iminomethane]chlorin (TPCF20) and its zinc(II) complex (ZnTPCF20) onto glass surfaces (GS-PS). The glass substrates were first etched and functionalized with amine groups by silanization. Subsequently, the photosensitizers (PSs) were covalently bonded to the surfaces through an ipso-fluoro aromatic nucleophilic substitution reaction. Fluorescence microscopy confirmed a uniform distribution of PSs, while morphological analysis demonstrated consistent and homogeneous coating. Additionally, contact angle measurements indicated increased lipophilicity of the modified surfaces. Spectroscopic analysis verified the presence of characteristic absorption bands of the macrocyclic PSs on the GS-PS. Photodynamic studies revealed singlet molecular oxygen as the primary reactive oxygen species generated by GS-PS. PDI assays using individual Staphylococcus aureus cells adhered to the surfaces showed complete bacterial inactivation after 10 mins of light exposure. In bacterial suspension assays, GS-PS achieved >99.9999 % reduction in bacterial viability (corresponding to a > 6 log reduction) after 45 min of irradiation. These results demonstrate that GS-PS materials incorporating chlorin derivatives are highly effective in microbial inactivation, offering strong potential for maintaining aseptic conditions on surfaces.