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H. So, M. A. Brook, H. Sheardown; PEG-Silicone Foams for Ophthalmic Drug Delivery. Invest. Ophthalmol. Vis. Sci. 2010;51(13):5309.
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Silicones are widely used in ophthalmic biomaterials for their exceptional properties. However, their hydrophobic nature often leads to adverse biological interactions. In order to ameliorate these effects, a hydrophilic polymer such as poly(ethylene) glycol (PEG) can be introduced into silicone elastomer formulations. Different end group functionalities of PEG can be exploited which gives rise to foamed structures that can act as drug delivery vehicles. Their porous nature gives these foamed materials enhanced surface area which can prove advantageous for sustained release.
The foams were prepared using the commercially available Sylgard 184 Silicone Elastomer Kit; additional Si-H groups were introduced by adding poly(hydromethylsiloxane). Different end-group functionalities (dihydroxy, monoallyl-, and diallyl-) of PEG were mechanically blended with the elastomer formulation separately and allowed to cure. Surface and bulk morphologic properties were examined using SEM. Interactions of the different functionalized PEG-silicone foams with immortalized human corneal epithelial cells were examined. Release of human serum albumin (HSA) as a model biomolecule was assessed to determine the ability of the foamed materials to provide sustained release.
Surface and bulk incorporation of the functionalized PEGs were confirmed using the energy dispersive X-ray tool on the SEM. Droplet structures were found within the material with varying sizes depending on the functionality; grafted PEG-silicone polymers are believed to stabilize the interface with the continuous medium, while PEG comprised the droplet core. The PEG-silicone foam materials showed low adherence with ophthalmic cell lines. In addition, release of HSA demonstrated that the foam material can act as an effective material to release this model protein.
Different end-group functionalized PEGs were successfully incorporated with commercial silicone elastomers creating foamed structures. The resulting PEG-silicone foams were capable of releasing the model biomolecule HSA. The use of the highly reactive allyl end group permits the tethering of different molecules, expanding the range of bioactive materials that can be released.
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