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Negar Babaei Omali, Lakshman N Subbaraman, Chantal Coles-Brennan, Zohra Fadli, Lyndon William Jones; Selective uptake of lysozyme by various hydrogel contact lens materials . Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6109.
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Contact lenses have been shown to deposit tear film components within hours of wear which may be a contributing factor to clinical performance. Lysozyme is a beneficial protein in the tear film and is part of the eye’s innate defense mechanism. The goal of this work was to evaluate the selective uptake of lysozyme compared to other tear proteins by hydrogel contact lens materials after exposure to an artificial tear solution (ATS).
Six hydrogel CL materials (etafilcon A with polyvinylpyrrolidone (PVP), polymacon, nelfilcon A, omafilcon A, ocufilcon B and nesofilcon A) were evaluated, wherein one set of lenses was soaked in an ATS to determine total protein uptake and another set was soaked in an ATS containing 125I-labeled lysozyme, lactoferrin or albumin to specifically measure the individual three proteins. Both sets of lenses were incubated for 16 h at 37°C. Lenses incubated in ATS were extracted using a solution containing 0.2% trifluroacetic acid in 50/50 water: acetonitrile solution and total protein uptake was determined using a standard Bradford assay. Lenses soaked in radiolabeled proteins were rinsed in phosphate buffered saline and radioactive counts were measured directly on lenses using a Gamma Counter. Individual protein uptake on lenses was measured using calibration curve plotting radioactive counts versus protein concentration.
Etafilcon A deposited the highest amount of total protein (568.3±45.4 µg/lens) with the majority represented by lysozyme (94%) (p<0.0001). The amount of total protein deposited on ocufilcon B was of 206.6±42.2 µg/lens with 96% of the uptake represented by lysozyme. The amount of lysozyme deposited on omafilcon A, nesofilcon A, nelfilcon A and polymacon was less than 20 μg/lens. When compared to lactoferrin and albumin, significantly higher levels of lysozyme deposited on etafilcon A, ocufilcon B, nesofilcon A and omafilcon A materials (all p=0.0001).
The quantity and nature of proteins deposited on CLs varies depending upon the chemical composition of the lens material. Among the various lenses tested, etafilcon A deposited the highest amount of total protein, most of it represented by lysozyme, a beneficial protein present in the tear film. Further investigation is needed to understand whether this is a contributing factor to clinical performance.
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