Selective Imaging and Inactivation of Bacteria over Mammalian Cells by Imidazolium-Substituted Polythiophene

Antibiotic-resistant bacterial infections have become a serious public health threat. In an effort to address this threat, we develop an imidazolium-functionalized conjugated polyelectrolyte that exhibits profound light-activated biocidal activity. Here we report the synthesis, photophysical properties, and biocidal activity of a regioregular head-to-tail polythiophene substituted with cationic imidazolium units (P3HT-Im) prepared by Grignard metathesis controlled polymerization. In water, P3HT-Im has a broad absorption in the visible region and exhibited a remarkably high biocidal efficiency with both Gram-positive and Gram-negative bacteria at sub-microgram per milliliter concentrations. Moreover, mammalian cell studies suggest that P3HT-Im is nontoxic to mammalian cells at concentrations of ≤20 μg/mL over a short time scale (≤1 h) in the dark and light, and the targeting rate-dependent selective mechanism is revealed. This study demonstrates the capability of P3HT-Im to achieve selective imaging and inactivation of bacteria over mammalian cells, suggesting that the polymer has significant potential for ameliorating antibiotic-resistant bacteria in a clinical setting.