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 hydrophilic aminoglycoside 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 antibiotic. PEG was combined with the macromer TRIS to create the model silicone hydrogel materials. The optical and physical properties of the novel TRIS-<i>co</i>-PEG silicone hydrogels 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. Drug release could be influenced through PEG content and was found to fit Higuchi-like 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 structure and properties of PEG, which alter the types of water found in each formulation and the water content.

通过隐形眼镜材料递送药物具备诸多显著优势。然而，高含水率材料（如水凝胶（hydrogel））易伴随药物突释现象，亲水性药物的控释往往难以达成。有机硅水凝胶（silicone hydrogel）凭借更强的疏水性与曲折的孔隙结构，可克服传统水凝胶材料的部分局限，在药物递送领域拥有可观应用潜力。本研究旨在探究含模型聚乙二醇（polyethylene glycol, PEG）的有机硅水凝胶用于递送亲水性氨基糖苷类抗生素（aminoglycoside antibiotics）的应用潜力。研究假设：作为在生物医学领域已得到广泛应用的聚合物，聚乙二醇除可赋予材料亲水性与抗蛋白吸附性能外，还可作为调控该亲水性抗生素递送的有效机制。研究中将聚乙二醇与大分子单体（macromer）TRIS复配，制备得到模型有机硅水凝胶材料。新型TRIS-共聚PEG（TRIS-co-PEG）有机硅水凝胶的光学与物理性能表现优异：具备极佳透光性、适宜的折射率与高透光率，表明材料仅存在极轻微的相分离现象。在广泛的配方范围内，材料均可保持优异的润湿性与抗蛋白吸附性能。研究发现，材料含水率与环氧乙烷含量呈高度正相关。药物释放行为可通过聚乙二醇含量进行调控，且其释放动力学符合类Higuchi动力学（Higuchi kinetics）特征。整体而言，本研究证实，将聚乙二醇引入模型有机硅水凝胶中，可实现亲水性化合物的控释。相关数据表明，该效果与聚乙二醇的独特结构与性能密切相关——聚乙二醇可改变各配方体系内水的存在形式与材料含水率。