Abstract
Purpose: :
To investigate the effects of the addition of crosslinked hyaluronic acid (HA) on model contact lens materials.
Methods: :
pHEMA and pHEMA/TRIS (silicone) hydrogels were synthesized using a UV chamber. HA of varying molecular weights was loaded into these materials and then crosslinked using EDC. Advancing water contact angle analysis and XPS analysis were performed on pHEMA and pHEMA/TRIS hydrogels (n ≥ 3). Equilibrium water content was determined for pHEMA/TRIS hydrogels (n=3). In vitro lysozyme activity and total lysozyme adsorption assays were also performed.
Results: :
The mean advancing water contact (AWC) angles (in o) for pHEMA hydrogels were 72.8 ± 3.1, 55.9 ± 6.6, 55.8 ± 5.0 and 47.9 ± 4.4 for control, 6.3 kDa HA, 35 kDa HA and 169 kDa HA, respectively. Mean AWC angles for 90% pHEMA 10% TRIS hydrogels were 85.8 ± 5.0, 69.1 ± 3.2, 65.2 ± 4.0 and 64.5 ± 2.5 degrees for control, 6.3 kDa HA, 35 kDa HA and 169 kDa HA, respectively. In all cases, the addition of crosslinked HA to these materials resulted in a significant reduction in contact angles (p<0.01). XPS revealed changes in the surface for pHEMA, 90% pHEMA 10% TRIS and 95% pHEMA 5% TRIS hydrogels with the addition of 35 and 169 kDa HA. The mean equilibrium water content (EWC) of 95% pHEMA 10% TRIS hydrogels at 24 hrs was 34.9 ± 0.3, 40.8 ± 0.2, 47.6 ± 0.2 and 37.2 ± 1.6 percent for control, 6.3 kDa HA, 35 kDa HA and 169 kDa, respectively. The addition of 6.3 and 35 kDa HA significantly increased the EWC of all materials (p<.0001). HA significantly reduced lysozyme adsorption of pHEMA hydrogels (p<.0001). The mean percentage of active lysozyme adsorbed on pHEMA hydrogels was 29.4 ± 10.8, 38.9 ± 9.5, 48.5 ± 30.3 and 57.9 ± 16.2 for control, 4.7 kDa HA, 35 kDa HA and 169 kDa HA, respectively. The addition of crosslinked HA significantly increased the percentage of active lysozyme (p<0.05).
Conclusions: :
Crosslinked HA increased the hydrophilicity of pHEMA and pHEMA/TRIS hydrogel materials, reduced lysozyme deposition and reduced the degree of lysozyme denaturation.
Keywords: contact lens • cornea: tears/tear film/dry eye