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Myrto Korogiannaki, Heather Sheardown; Surface Modified Contact Lenses with a Wetting Agent for Improved Comfort. Invest. Ophthalmol. Vis. Sci. 2014;55(13):4658.
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© ARVO (1962-2015); The Authors (2016-present)
Ocular dryness and discomfort are two of the main reasons of contact lens (CL) discontinuation, mainly attributed to increased friction between the lens and the ocular surface that causes reduced vision or even inflammation; and poorly hydrated CL surfaces. Re-wetting eye drops that contain hydrophilic polymers, such as hyaluronic acid (HA), are applied to counteract dryness. However, their efficiency is limited due to short residence time. Hence, the design of a comfortable CL is desirable. This work aims to generate innovative CL materials with improved interfacial properties by coating the surface of poly(2-hydroxyethyl methacrylate) (pHEMA) CL with a biocompatible layer of HA.
Model pHEMA hydrogels were synthesized by UV-induced free radical polymerization. The conjugation of HA on the lens’ surface was accomplished by thermal crosslinking of thiolated HA (SH-HA) (MW 5 kDa) with the acrylated pHEMA surfaces during autoclaving. SH-HA was verified by NMR spectroscopy. ATR-FTIR spectra were used to evaluate the reaction of acryloyl chloride with the hydroxyl groups (-OH) of the surfaces and the chemistry of the grafted surfaces. Water contact angles, protein sorption, surface lubricity and morphology were also assessed.
SH-HA of 90% yield was obtained through the covalent attachment of cysteamine hydrochloride onto the carboxyl groups of HA (38% degree of substitution) and confirmed with a resonance at 2.9 ppm according to NMR spectra. ATR-FTIR graphs showed successful esterification reaction as a new peak at 1650 cm-1 attributed to the carbon-carbon double bonds (-C=C) and a significant decrease in the broad peak of the -OH groups (3000- 3500 cm-1) of the pHEMA surfaces were observed. Upon thermal conjugation, the peak of the -OH functional groups was reinforced suggesting the contribution of the -OH groups from HA and a new small peak found at 1040 cm-1 was assigned to the ether groups of HA. A decrease in water contact angles and protein sorption on the grafted surfaces suggested increased surface wettability and hydrophilicity (p<0.05) when compared to the unmodified discs.
Surface coating of pHEMA gels with a HA boundary layer may offer improved surface characteristics. Hence, these novel pHEMA CL might have the potential to alleviate CL induced dryness and discomfort, ameliorating the visual health of millions of people around the world.
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