(145f) Evaluating the Cytotoxicity of Conjugated Polyelectrolyte Biocides

An estimated 19,000 deaths and $3-4 billion in health care costs per year in the U.S. are attributed to methicillin-resistant Staphylococcus aureus (MRSA) infections. Infected individuals inevitably touch a wide variety of surfaces. Therefore, making these surfaces antimicrobial would reduce or prevent the spread of potentially untreatable strains of bacteria. Current sterilization and disinfection techniques tend to be temporary and surface-specific, and require constant vigilance on the part of medical and support staff. Certain conjugated polyelectrolytes (CPEs) with arylene ethynylene repeat unit structure have been demonstrated to exhibit dark and light-activated antimicrobial activity. Both in solution and anchored to a support, these polymers have been effective at killing Gram-negative bacteria, specifically Pseudomonas aeruginosa strain PAO1 and Cobetia marina. This light-activated antimicrobial activity enables their use in a wide range of potential applications. However, until recently, it was unknown if the CPEs would exhibit similar biocidal activity toward mammalian cells. In this study, bovine aortic endothelial cells were exposed to two different CPEs for increasing periods of time, from 10 minutes to 24 hours, in both light and dark conditions. The relative cytotixicity was then assessed using a live/dead fluorescence assay, and imaged via epi-fluorescence microscopy. While CPEs demonstrate biocidal activity toward P. aeruginosa strain PAO1 and C. marina, these polymers do not appear to be toxic toward mammalian cells when the cells are exposed to the polymers in both light and dark conditions. Further work is underway to evaluate cytotoxicity at concentrations above the micromolar concentrations tested to date, to correlate mammalian test conditions to bacterial test conditions, and to include an epithelial cell line. Because membrane disruption is a common mechanism of action for antimicrobial agents, molecular dynamic simulations will also be performed to model polymer insertion into a hydrated zwitterionic phospholipid bilayer. These combined data are important to determine how to best incorporate CPEs into antibacterial household and health care products.