Photodynamic antimicrobial activities of a series of meso-substituted 2,6-dibrominated 1,3,5,7-tetramethylBODIPY dyes

The photodynamic antimicrobial chemotherapy (PACT) activities of seven 1,3,5,7-tetramethyl-2,6-dibromoBODIPY dyes with 4-acetamidophenyl (2a), 2-iodophenyl (2b), 3-iodophenyl (2c), 4-iodophenyl (2d), 2-bromophenyl (2e), 5-bromothien-2-yl (2f), and methylphenyl ester (2g) meso-substituents were studied against Staphylococcus aureus through irradiation with a 530 nm Thorlabs M530L3 light emitting diode (LED) (110 mW.cm${}^{-2})$ to identify structure-property relationships related to modifying the meso-substituent. Significant differences are observed in the log${}_{10}$ reduction values obtained with 1 $\mu$M of 2a exhibiting the highest PACT activity with a value of 9.60 after 15 min of photoirradiation. In contrast, log${}_{10}$ reduction values < 1.20 were obtained after 60 min of photoirradiation for iodophenyl dyes 2b-2d. The data demonstrate that the singlet oxygen quantum yield of the dye is not the most important factor determining the PACT activity properties.