Lactoferrin Uptake Kinetics on SiH and Conventional Hydrogel Contact Lens Materials

Lakshman N Subbaraman¹ ,BSOptom, MSc, FAAO, Lisa M Chow¹, BSc, Heather Sheardown², PhD, Lyndon Jones¹, PhD, FCOptom, FAAO

¹ Centre for Contact Lens Research, University of Waterloo, Waterloo, ON, Canada.
² Department of Chemical Engineering, McMaster University, Hamilton, ON, Canada.

PURPOSE: To compare the kinetics of lactoferrin deposition on silicone hydrogel (SH) and FDA group II (GpII) and group IV (GpIV) conventional hydrogel contact lens materials by artificially doping lenses with ¹²⁵I labeled lactoferrin solution.

METHODS: Seven different contact lens materials - two conventional (etafilcon A - GpIV and omafilcon A - GpII) and five SH (lotrafilcon A, lotrafilcon B, balafilcon A, galyfilcon A and senofilcon A) were incubated in 1 ml of simple lactoferrin solution containing 125I labeled lactoferrin. The lenses were incubated for time periods ranging from 1 hour to 28 days at 37 °C with constant shaking. Following the specified incubation period, the lenses were rinsed briefly with phosphate buffered saline to remove unbound protein and were then placed in polypropylene tubes. The radioactive counts on the lens materials were determined using an Automatic Gamma Counter.

RESULTS: There was a gradual increase in lactoferrin deposition on all the lenses across all time points. At the end of 28 days the amount of lactoferrin/lens in µg was 11.3±1.9 for etafilcon A, 6.8±2.0 for omafilcon A, 2.1±0.9 for lotrafilcon A, 3.1±1.0 for lotrafilcon B, 11.8±2.9 for balafilcon A, 5.4±1.1 for galyfilcon A and 5.6±0.6 for senofilcon A. After 28 days, etafilcon A and balafilcon A deposited lactoferrin to the greatest degree (p<0.05), but these were not different from each other (p=0.48), while lotrafilcon A and B deposited the least (p<0.05 vs other lenses; p=0.57 with each other). Galyfilcon A, senofilcon A and omafilcon A lens materials deposited intermediate levels of lactoferrin (p<0.05 compared with other lenses; p>0.05 with each other).

CONCLUSIONS: Radiochemical analysis is a sensitive and effective technique to determine the small quantities of lactoferrin deposited on SH lenses. Kinetics of lactoferrin deposition on contact lens materials varies depending on the chemical structure of the lens material under consideration.