Purchase this article with an account.
Frances Lasowski, Heather Sheardown; Silicone Hydrogels as Drug Delivery Devices for Various Ocular Therapeutics. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):6072.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Contact lenses are an attractive, minimally-invasive alternative to eye drops for various ocular therapeutics, such as roscovitine, atropine and timolol maleate for use in retinoblastoma, myopia and glaucoma conditions respectively. However, the uptake and release characteristics of these drugs vary greatly depending on the properties of the silicone hydrogel. Therefore, model lenses containing various drug loadings have been developed to determine the effect of material composition on subsequent drug release.
The model lenses contained various combinations of dimethylacrylamide (DMA), methacryloxypropyltris(trimethylsiloxy)silane (TRIS) and a hydroxyl-modified TRIS (modified TRIS). Drugs were loaded into the materials either directly during synthesis or by subsequent swelling in a drug solution. Release studies were performed into PBS solutions using UV- spectroscopy and HPLC to quantify release of each drug. Swelling, extraction, uptake and contact angle studies were also completed to characterize the materials.
Most materials showed an appropriate water content (greater than 20%). The incorporation of the modified TRIS resulted in a quicker drug release for materials where the drug was directly loaded into the materials, though many showed sustained release greater than two weeks. As anticipated, materials containing both regular and modified TRIS (such as 80:10:10 DMA:TRIS:modified TRIS) showed drug release levels in between that of the single-silicone materials, though the release was more similar to the regular TRIS (such as 80:20 DMA:TRIS); this is seen in Figure 1 for one of the drugs studied. Similarly materials with greater DMA content tended to release the drugs faster than those with lower DMA contents. These results demonstrate that the drug release is highly correlated to the swelling of the material, though the amount of drug loading and method of loading is also important.
Alterations to the amount and method of drug loading, as well as the material compositions, alter the drug release kinetics. It is possible to sustain drug release for two weeks, the normal wear time of a contact lens, while maintaining appropriate contact lens material properties. This shows contact lenses are feasible for drug delivery to various ocular tissues.
This PDF is available to Subscribers Only