Investigating the Effects of Commercial Antimicrobial Agents on Human Corneal Epithelial Cell Membranes

Multi-purpose solutions (MPS) are a single solution that functions to simultaneously rinse, disinfect, clean and store soft contact lenses. Several commercial MPS products contain polyhexamethylene biguanide (PHMB) and/or polyquaternium-1 (PQ-1) as antimicrobial agents. In this proster we report the effects of PHMB and PQ-1 on small unilamellar vesicles (SUV) that we have designed to mimic the average human corneal epithelial cell membrane. Specifically, we assessed the interactions of PHMB and PQ-1 on the biomembrane by using fluorescence spectroscopy, dynamic light scattering (DLS), and liquid chromatography/mass spectrometry (LC-MS). Fluorescence assessed the membrane surface polarity and stability through the temperature-dependent generalized polarization (GP), the gel-to-liquid transition temperature (Tm) and the associated van’t Hoff enthalpy (ΔHVH) as a function of PHMB and PQ-1 concentration. DLS evaluated SUV aggregation as a function of PHMB and PQ-1 concentration and SUV composition. LC-MS determined the composition of any precipitates that formed. PHMB association with the mimic SUV bilayer leads to: (i) a decrease in surface polarity, (ii) an increase in (Tm), (iii) an increase in phospholipid-phospholipid cooperativity, and (iv) an increase in SUV size on a nanometer scale. PQ-1 association with the mimic SUV bilayer leads to: (i) an increase in surface polarity (ii) no change in (Tm), (iii) no change in phospholipid-phospholipid cooperativity, and (iv) an increase in SUV size on a micron scale due to SUV aggregate formation. The aggregates exhibited a phospholipid composition equivalent to the SUV prior to the addition of PQ-1. These results are consistent with PHMB adsorbing onto and PQ-1 intercalating into the mimic SUV bilayer structures.