Iodinated xanthene-cyanine NIR dyes as potential photosensitizers for antimicrobial photodynamic therapy

Photosensitizers (PSs) are chemical entities that upon light exposure are able to produce cytotoxic species such as singlet oxygen superoxide and free radicals. PSs are used in photodynamic therapy applications (PDT) to eradicate cancer cells, pathogenic bacteria, fungi, and viruses. Development of the NIR-activatable photosensitizes with high phototoxicity and low toxicity in dark conditions is challenging. Here we first report on the synthesis and antimicrobial testing of the new NIR photosensitizers based on the iodinated xanthene-cyanine dyes. These new photosensitizers exhibit high antimicrobial efficacy on Staphylococcus aureus pathogens at low dye concentration (~0.5 μM) and low NIR light dose (24.3 J/cm2). [Display omitted] •Non-iodinated, mono-iodinated and di-iodinated xanthene-cyanine dyes were synthesized.•Spectral properties and antimicrobial photodynamic activity were investigated.•These dyes exhibit high phototoxicity towards S. aureus pathogens at low concentration.•These NIR dyes more efficiently eradicate S. aureus compared to ICG.•An increase in the number of iodine atoms enhances phototoxicity.