| Objective: To assess molecular level interactions of polyhexamethylene biguanide (PHMB) and human corneal epithelium membranes using an in vitro model.
Method: We developed an in vitro liposome model that mimics the human corneal epithelial cell surface. The liposome membrane integrity after being exposed to free fluorescein, PHMB, and PHMB tagged with fluorescein isothiocyanate (FTIC) was determined by changes of the melting temperature and steady-state fluorescence anisotropy.
Results: Liposomes showed no statistically significant interaction with free fluorescein. However, PHMB tagged with FTIC demonstrated a considerable association with the liposomes (p < 0.0002). Liposome integrity measurements demonstrated no statistically significant change in the melting temperature, Tm, relative to body temperature (37oC) when exposed to PHMB (P > 0.05) between 0 and 100 ppm.
Conclusions: The newly developed in vitro model study demonstrates that PHMB has a non-destructive interaction with the surface of liposomes derived from the known phospholipid profile of human corneal epithelial cells, even at concentrations 100-times higher than in commercially available multi-purpose contact lens care solutions. Based on the molecular evidence presented, transient hyperfluorescence appears substantially different from corneal staining that results from pathological injury. Transient hyperfluorescence may be an inappropriate tool for evaluating biocompatibility of contact lens and lens care products. |
