Altering the release of tobramycin by incorporating poly(ethylene glycol) into model silicone hydrogel contact lens materials.

Delivery of drugs from contact lens materials is attractive for a number of reasons. However, the controlled delivery of hydrophilic drugs can be difficult to achieve due to the burst release of drug that is associated with materials of high water content, such as hydrogels. Silicone hydrogels have significant potential for drug delivery due to their increased hydrophobicity and the tortuous nature of the pores, overcoming some of the limitations associated with conventional hydrogel materials. The aim of this study was to examine the potential of model poly(ethylene glycol) (PEG) containing silicone hydrogels for delivery of the hydrophilicaminoglycoside antibiotics. It was hypothesized that PEG, a polymer that has seen extensive use in biomedical applications, will provide, in addition to hydrophilicity and protein repulsion, a mechanism for controlling the delivery of this hydrophilic drug. PEG was combined with the macromer TRIS to create the model silicone hydrogel materials. The optical and physical properties of the novel TRIS-co-PEG silicone hydrogels demonstrated that the materials exhibited excellent transparency, appropriate refractive index and high transmittance indicating minimal phase separation. Desirable properties such as wettability and protein repulsion were maintained across a wide range of formulations. The water content was found to be highly correlated with the ethylene oxide content. Tobramycin release could be altered and was found to fit Higuchi kinetics. Overall, the study demonstrates that incorporation of PEG into a model silicone hydrogel could be used to control the release of a hydrophilic compound. Data suggests this is related to the unique hydrogen-bonding activity of PEG, which alters the types of water found in each formulation and the EWC.