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A. K. Weeks, L. Jones, H. Sheardown; Incorporating HA as an Internal Wetting Agent. Invest. Ophthalmol. Vis. Sci. 2009;50(13):5651.
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© ARVO (1962-2015); The Authors (2016-present)
Internal wetting agents have been widely shown to decrease protein uptake and increase comfort of contact lens materials. It was of interest in this study to investigate the effects of hyaluronic acid (HA) as a wetting agent on lysozyme sorption and denaturation on one conventional and two silicone hydrogel model contact lens materials.
Model conventional and silicone hydrogels comprised of pHEMA, pHEMA/TRIS and DMAA/TRIS hydrogels were synthesized using UV polymerization. HA of varying molecular weights (ranging from 4.7 to 910 kDa) was covalently incorporated into these materials using previously developed methods. Photocrosslinkable HA was also incorporated into pHEMA hydrogels during the synthesis phase. Lysozyme adsorption and in vitro lysozyme activity were measured to determine the effect of the incorporated HA on the adsorption since protein interactions with lens materials are known to impact comfort.
The presence of HA significantly reduced lysozyme sorption (p<0.05) in pHEMA hydrogels with the modified hydrogels sorbing only 10-16% of that taken up by the control. The mean percentage of active lysozyme sorbed varied between 37.3 ± 2.1 and 85.2 ± 11.0%, depending on the molecular weight of HA incorporated, with all molecular weights decreasing lysozyme denaturation (p<0.05). Similarly, the amount of protein associated with the pHEMA/TRIS hydrogels decreased significantly (p<0.001) with the modified hydrogels sorbing 16% of that of the control. The percentage of active lysozyme varied between 50.7 ± 1.4 and 51.2 ± 21.0% for the HA-containing hydrogels, which was significantly higher than the control where only a small fraction of lysozyme was active. The more relevant DMAA/TRIS hydrogels sorbed only 20% of the controls (p<0.001). pHEMA hydrogels containing photocrosslinkable 132 kDa HA sorb less lysozyme than pHEMA controls (p<0.05).
The presence of HA as an internal wetting agent significantly reduces lysozyme sorption and leads to lower denaturation of the sorbed protein. Therefore, the incorporation of HA may lead to improved contact lens comfort.
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