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Frances Lasowski, Genevieve Conant, Heather Sheardown; Exploring Silicone Hydrogel Material Properties to Deliver Various Ocular Therapeutics. Invest. Ophthalmol. Vis. Sci. 2014;55(13):6044.
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A minimally invasive device is ideal for the delivery of therapeutics to treat ocular conditions, such as roscovitine to prevent retinoblastoma, atropine to retard myopia progression and timolol maleate to treat glaucoma. Contact lenses represent an attractive option as an alternative vehicle to eye drops for these therapeutics, and model lenses have been developed with different drug loadings to examine the effect of material composition on this drug release.
Model lens materials were based on combinations of dimethylacrylamide (DMA), methacryloxypropyltris(trimethylsiloxy)silane (TRIS) or a hydroxyl-modified TRIS (TRIS-OH) in 70:30 and 80:20 DMA:TRIS (regular) or DMA:TRIS-OH (modified) mole ratios. The materials for direct loading were prepared with and without roscovitine (0.5 wt%), timolol maleate (0.5 wt%) and atropine (0.5 wt% and 2 wt%). Release studies were performed into PBS solutions using UV- spectroscopy and HPLC to quantify release of each drug. Swelling, extraction, TEM, DSC and contact angle studies were done to characterize the materials.
All materials showed water contents above 20% except for the 70/30 regular materials, which only had 15.8% water content. For all materials with direct loading, the incorporation of TRIS-OH resulted in faster drug release from the materials over the regular combination. The 80/20 materials released the drug faster than the 70/30, with the exception of roscovitine, where the modified 70/30 materials showed the fastest release. A sample release is shown in Figure 1. These results demonstrate that the drug release is highly correlated to the swelling of the material, though the amount of drug loading is also important. It is possible to achieve sustained drug release for all three drugs for 2 weeks with these materials.
Contact lenses provide a feasible method to deliver a variety of drugs to various ocular tissues. By adjusting the drug loading and material compositions, it is possible to prolong drug release while maintaining appropriate contact lens material properties.
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