Improvement of the surface wettability of silicone hydrogel films by self-assembled hydroxypropyltrimethyl ammonium chloride chitosan mixed colloids

A novel kind of hydroxypropyltrimethyl ammonium chloride chitosan (HACC) mixed colloid was developed to improve the hydrophilicity of silicone hydrogel films (SHFs) via self-assembly. The contact angle of the modified SHF decreased from 33.24 degrees to 12.98 degrees, whereas the atomic force microscopy image verified that the roughness of the modified films decreased and indicated that the HACC mixed colloids filled in the interstices on the surface of the SHF. A new method of capacitance was developed to characterize the electric charge value, the groups, and the microscopic conditions of the self-assembled SHF surface for the first time. Cyclic voltammetry and chronopotentiometry exhibited that the capacitance of the SHF increased to 0.0196 F/g, which indicated the enhanced positively charged surface and increased the number of hydrophilic quaternary ammonium groups on the surface. Lipid adsorption analysis also revealed that the modified SHF possessed a weaker lipid adhesion ability and stronger lipid removal ability than those of the original SHF and hence showed promising features for application in ophthalmological products.