Hyaluronic acid containing hydrogels for the reduction of protein adsorption

Recently, new contact lens materials have been introduced which are reported to improve comfort by incorporating wetting agents either in a releasable or nonreleasable form. In the present work, model lens materials based on poly(2-hydroxyethyl methacrylate) (pHEMA) were developed which incorporate releasable or crosslinked and therefore physically entrapped hyaluronic acid (HA) of various molecular weights as a wetting agent. Crosslinked HA, despite being only present in very small amounts, resulted in consistently lower water contact angles over 4 h in comparison to controls, indicating that HA is present at the interface and was not being released over time. The presence of HA in the material was further confirmed by increases in the glass transition temperature measured by differential scanning calorimetry (DSC), and small increases in the stiffness as measured by Instron testing. This crosslinking procedure appeared to have no effect on optical transparency using 35 kDa HA, whereas small decreases in optical transparency at higher wavelengths were noted for the 169 kDa HA crosslinked material, as measured by UV spectrophotometry. Most importantly, protein adsorption results indicated that the adsorption of all proteins studied was considerably decreased by the presence of the small amount of crosslinked HA. The results provide insight into the mechanisms of comfort improvement with commercially available lens materials and suggest that HA containing materials may have significant potential for use in contact lens applications.