The effect of the poly(ethylene glycol) chain on surface exchange of rigid gas-permeable contact lenses.

Purpose: The SEED Company, Ltd. developed the novel SEED S-1, a rigid gas-permeable contact lens (RGPCL) with a hydrophilic monomer grafted onto its surface by polymerization. This article describes the use of the polymerized graft material poly(ethylene glycol) (PEG) used as a biomaterial, and characterizes the surface of the RGPCL.

Methods: The grafting of PEG onto a RGPCL was carried out by plasma treatment and polymerization, and the characteristics of the RGPCL surface were obtained by measuring the water equilibrium contact angle and the surface zeta potential. The zeta potential was measured using an electrophoretic light-scattering photometer. Furthermore, the characteristics of the interaction between the polymer surface and protein was obtained by observing the relationship of adsorption between the protein and lipids and the polymer surfaces.

Results: The RGPCL became hydrophilic with increasing ethylene glycol units when the graft was polymerized onto the otherwise hydrophobic surface. After the graft polymerization of PEG onto the RGPCL, the surface zeta potentials increased to a negative static surface with the increased addition of ethylene glycol units. Additionally, the amount of adsorption of protein and lipids were decreased, respectively, as the ethylene glycol chain increased in length.

Conclusions: The hydrophobic surface of the RGPCL was changed to a hydrophilic surface by graft polymerization of PEG. This suggests that novel RGPCL surfaces can be designed by graft polymerization, using such ethylene glycol groups.