“End-Only” Functionalized Oligo(phenylene ethynylene)s: Synthesis, Photophysical and Biocidal Activity

It is essential to develop alternative strategies to treat infections, especially those infections caused by Staphylococcus aureus, which is responsible for most skin infections. Among those strategies, light-induced inactivation of pathogens appears to be a promising candidate. We present four novel “end only” oligo(phenylene ethynylene)s (EO-OPE-1s) that have the ends functionalized with cationic groups and are powerful light-activated biocides against Escherichia coli, Staphylococcus epidermidis, and S. aureus . We have correlated the light-induced biocidal activities with singlet oxygen quantum yields Φ ( 1 O 2 ) of EO-OPE-1s, and a higher Φ ( 1 O 2 ) correlates with a better light-induced biocidal activity. Coupled with our previous work on the interactions of EO-OPE-1s with dioleoyl- sn -glycero-3-phosphocholine (DOPC)/cholesterol vesicles, we believe the biocidal process involves the following: (1) EO-OPE-1s penetrate the bacterial membrane, (2) EO-OPE-1s photosensitize the generation of singlet oxygen and/or other reactive oxygen species, and (3) singlet oxygen and/or reactive oxygen species trigger the cytotoxicity.