Improvement of the surface wettability of silicone hydrogel contact lenses via layer-by-layer self-assembly technique

The surface wettability and anti-protein adsorption of a silicone-based hydrogel that was synthesized by a block copolymer of polydimethylsiloxane (PDMS) and poly (ethylene glycol) methacrylate (PEGMA) was improved via polyelectrolyte multilayer (PEM) immobilization. Polysaccharide PEMs of chitosan (CS, as a positive-charged agent) and hyaluronic acid (HA, as a negative-charged and anti-adhesive agent) were successfully assembled on the PDMS-PU-PEGMA silicone hydrogel in a layer-by-layer (LBL) self-assembly manner. Atomic force microscopy (AFM) and dyeing data verified the progressive buildup of the PEM silicone hydrogel. The results showed that the contact angle of the silicone hydrogel decreased with an increase in the number of PEM grafting layers. Furthermore, after immobilizing five layers of CS/HA, the protein adsorption decreased from 78 ± 11 to 26 ± 4 μg/cm(2) for HSA and from 55 ± 10 to 20 ± 4 μg/cm(2) for lysozymes. This indicates that CS/HA PEM-immobilized silicone hydrogels can resist protein adsorption. Furthermore, these hydrogels were non-cytotoxic according to an in vitro L929 fibroblast assay. Overall, the results demonstrated that the modified silicone hydrogels exhibited hydrophilicity and anti-protein adsorption, as well as relatively high oxygen permeability and optical transparency. Therefore, they would be applicable as a contact lens material.