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L. Muya, M. F. Mowrey-Mckee, G. Minno, F. Meadows; Determination of Binding of PHMB to Mucin. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4869. doi: https://doi.org/.
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© ARVO (1962-2015); The Authors (2016-present)
Polyhexamethylene biguanide (PHMB), an antimicrobial agent used in various contact lens care formulations, has been hypothesized to bind to ocular mucin found on the surface of conjuctival and corneal epithelial cells. The objective of these studies was to show whether or not PHMB binds to mucin.
The mucin and PHMB solutions were diluted with 0.1 M borate buffer, pH 7.21 to 0.5mg/mL and 40ppm respectively. All control samples were prepared using same borate buffer in place of the mucin solution. The solutions were incubated for 24 hours at 37°C. The mucin was separated from a 3 mL sample of each solution using a Centricon filter (10K molecular weight (MW) cutoff) by centrifugation. The mucin (MW > 10K) should be excluded by the membrane and should not appear in the filtrate whereas PHMB (MW < 10K) should pass freely into the filtrate. The filtrates were analyzed for PHMB spectrophotometrically at A220 - A290 (max PHMB = 237 nm). The amount of PHMB in the mucin-containing vs non-mucin containing filtrates was compared.
Mucin containing samples had greatly reduced amount of free (filterable) PHMB. Significant differences in PHMB concentration were observed between filtrates of the mucin-containing samples and the respective PHMB controls (no mucin) with the PHMB controls being consistently higher than the mucin-PHMB samples. A 20% reduction in absorbance was observed in the filtrate sample containing 5 mL of mucin (0.5 mg/mL) and 10 mL of PHMB (40 ppm) compared to the control filtrate (p= 0.0009).
Overall, the filtrates from all samples containing both PHMB and mucin had reduced PHMB levels compared to the PHMB controls without mucin which suggests complexation of the PHMB with mucin. These findings may have implications for studies such as those involving corneal staining.
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