Surface Self-assembly Coating And Properties Of PHEMA Hydrogel For Corneal Contact Lens

The hydrophilicity of the corneal contact lens is crucial to protein deposition;the better the hydrophilicity of the material,the less protein deposition will occur.Traditional PHEMA hydrogel corneal contact lenses have poor hydrophilicity and weak resistance to protein adsorption,and prolonged wear will lead to deposition of tear proteins on the surface of corneal contact lenses,which in turn will easily breed bacteria and lead to a series of problems such as corneal inflammation.To address these problems,a highly hydrophilic PHEMA corneal contact lens hydrogel material was constructed using layer-by-layer self-assembly technology.The hydrophilic PHEMA-MEC hydrogel was constructed by layer-by-layer self-assembly of positively charged polyallylamine hydrochloride（PAH）and negatively charged nano-Si O₂ on the surface of PHEMA hydrogel after oxygen plasma treatment to improve the surface hydrophilicity,anti-protein adsorption and anti-bacterial adhesion of PHEMA hydrogel.The properties of PHEMA-MEC hydrogels were investigated by characterization of infrared spectroscopy（FT-IR）,elemental energy spectroscopy（EDS）,scanning electron microscopy（SEM）,atomic force microscopy（AFM）,water contact angle,equilibrium water content,mechanical properties,light and oxygen permeability,tear protein adsorption,bacterial adhesion,drug loading and release,and cytotoxicity.（1）Exploration of modification conditions for self-assembled coatings of PHEMA hydrogels.The conditions of coating time,number of PAH/Si O₂ layers,PAH concentration,concentration of nano-Si O₂ dispersion,PAH/PAA pre-coating,and oxygen plasma treatment were explored.The parameters of the self-assembly coating process were optimized as follows:the single-layer coating time was 10 min,the number of PAH/Si O₂ layers was 6,the concentration of PAH solution was 0.1 mol/L,the mass fraction of nano-Si O₂ dispersion was 0.3%,the concentration of PAA solution was 0.01mol/L,the number of pre-coated PAH/PAA layers was 2,and the oxygen plasma treatment time was 15 min.（2）Performance of self-assembled coating modified PHEMA hydrogelsThe water contact angle test showed that the water contact angles of PHEMA,PHEMA-MEC₇,PHEMA-MEC₁₂ and PHEMA-MEC₂₂ hydrogels were 82.3°,17.0°,15.2°and 12.9°,respectively.FT-IR and EDS analysis showed that Si O₂ was successfully coated on the PHEMA hydrogel surface.SEM and AFM results showed that the surface of PHEMA hydrogel became rougher after constructing a multilayer electrostatic coating on the PHEMA-MEC₇ and PHEMA-MEC₂₂ hydrogels.PHEMA-MEC₁₂ was a little flatter than PHEMA-MEC₇ and PHEMA-MEC₂₂ hydrogel surfaces.The results of tear protein adsorption experiments showed that PHEMA-MEC₁₂hydrogel had the best anti-protein adsorption performance,with 49.5%and 49.2%less lysozyme and BSA adsorption compared to PHEMA hydrogel.The results of anti-bacterial adhesion experiments showed that the adhesion of S.aureus and E.coli on the surface of PHEMA-MEC₁₂ hydrogel was reduced by 62.5%and 41.8%,respectively,compared with PHEMA hydrogel.PHEMA and PHEMA-MEC₁₂ hydrogels had 10.52μg/mg and 12.68μg/mg of levofloxacin hydrochloride loading,respectively.PHEMA hydrogel completely released the loaded drug within 48 h,while PHEMA-MEC₁₂hydrogel could extend the drug release to 72 h,indicating that PHEMA-MEC₁₂hydrogel has a drug sustained release function.In conclusion,PHEMA-MEC₁₂hydrogel can not only significantly improve the surface hydrophilicity of PHEMA hydrogel,effectively reduce tear protein adsorption and bacterial adhesion,but also endow PHEMA hydrogel with a better drug sustained release.Thus,PHEMA-MEC hydrogel is a promising material for corneal contact lenses for the treatment of ocular diseases.