Investigation of Copper and Manganese Ion Diffusion through Hydrogel Contact Lens Materials Using ESR Technique

Diffusion of tear film components through a hydrogel contact lens is significantly influenced by its interactions with material. In our study Cu and Mn ions were used to describe transport properties of the membranes which were hydrogel contact lens materials. Ion concentrations were measured by an electron spin resonance (ESR) spectrometer, and differential scanning calorimetry (DSC) was used as a complementary technique. The materials investigated were nelfilcon A and etafilcon A. Diffusion D and permeation P coefficients were calculated. In both materials transport dynamics can be described by two stages (except for CuSO4 in etafilcon A), where the first is shorter and characterized by higher diffusion D and permeation P coefficients than the second one. The results obtained allowed us to make conclusions about the interactions between the ions and polymer chains that may happen inside the hydrogel matrix during diffusion, affecting transport