Light-Activated Antifungal Properties of Imidazolium- Functionalized Cationic Conjugated Polymers

Infections caused by pathogenic fungi, especially Candida albicans, are a growing global challenge for public health. Current antifungal drugs have been administered commonly to treat Candida infections, yet their high toxicity and the development of multidrug-resistant strains pose a threat. The present report describes the synthesis, characterization, and antifungal activity of a novel class of water-soluble conjugated polymers (CPs) bearing imidazolium functionality in the polymer backbone that combine both photodynamic and polyionic properties. The photophysical properties of the polymers were studied by steady-state and time-resolved spectroscopy, and all the polymers are demonstrated to generate reactive oxygen species. In vitro antifungal activity studies were performed with the CPs along with two other poly(p-phenylene ethynylene) polymers functionalized with imidazolium units in the side chains and an "end-only"-functionalized oligo(pphenylene ethynylene) oligomer. Antifungal activities of the CPs and oligomer were examined against C. albicans under three different modalities. Among them, the linear imidazolium polymers effectively controlled the growth of planktonic cells (MIC90 similar to 1 mu M) and biofilms (MIC90 similar to 8 mu M) and as well as eradicated the preformed biofilms (MBEC90 similar to 128 mu M) under a low dose (0.4-4.7 J/cm(2)) of visible light with low toxicity against mammalian cells. It is found that the structure and aggregation state of the CPs influence the antifungal property and cytotoxicity to human hepatocellular carcinoma (HepG2) cells.