Fabrication of stable hydrophilic coating on poly(2-hydroxyethyl methacrylate) hydrogel contact lens for tear protein deposition resistance based on oxygen plasma treatment and layer-by-layer self-assembly

Abstract Hydrophobicity is a main cause of tear protein deposition on poly(2-hydroxyethyl methacrylate) (pHEMA) hydrogel contact lenses. Surface coating is the simplest approach for hydrophilicity improvement, but its stability is still challenging. This study developed a combined technique based on oxygen plasma treatment and layer-by-layer (LBL) self-assembly of poly(allylamine hydrochloride) (PAH) and nano-silica (n-SiO2) to enhance the stability of hydrophilic coating on pHEMA hydrogel contact lenses. The coating conditions and stability were systematically investigated, and it was found that under an optimal condition, the water contact angle of pHEMA hydrogel significantly decreased from 83° to 16°; moreover, the coating exhibited an excellent stability in a 28-day immersion test, effectively resisting tear protein deposition (lysozyme and bovine serum albumin) and bacterial adhesion (Staphylococcus aureus and Escherichia coli). The modified pHEMA hydrogel was nontoxic to both L929 mouse fibroblasts and human immortalized keratinocytes. Additionally, it performed comparably or superiorly to the unmodified pHEMA hydrogel in terms of light transmittance, tensile properties, equilibrium water content, and oxygen permeability, while also slowing the outward diffusion of loaded drugs. These findings demonstrate that a coordination of oxygen plasma treatment and LBL self-assembly is a promising approach for enhanced stability of hydrophilic coating on hydrogel contact lenses.