The Effects of Concentration, pH, and Ionic Strength on Lysozyme Adsorption onto AA and HEMA Contact

Due to the presence of polar monomers acrylic acid (AA) and 2-hydroxyethyl methacrylate (HEMA) in the conventional hydrogel contact lenses, the major protein component of the human tear, lysozyme is extensively adsorbed onto their surfaces. The adsorption of lysozyme onto the surface of contact lenses leads to limitations in their applications. The presence of electrolytes in the human tear, in particular NaCl, affects the adsorption of lysozyme. The present study measures the concentration of lysozyme adsorbed from solutions with similar concentrations of artificial tear onto the surfaces of AA and HEMA hydrogels by UV spectroscopy. The adsorption results are treated by the Langmuir adsorption isotherm and the constants of this isotherm are evaluated. The effect of various factors such as protein concentration, ionic strength, pH and temperature on the adsorption of lysozyme are examined and discussed in the light of theobtained results.