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).