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M.A. Princz, H. Sheardown; Heparin and Growth Factor Modified Materials for Artificial Cornea Applications . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2751.
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As an alternative to cornea tissue transplants, artificial corneal devices are being explored. Proper integration of the device with host tissue and epithelial overgrowth can be manipulated by cytokine incorporation. Here, we investigate the delivery of growth factors in a soluble form, by using tethered heparin as the delivery vehicle, from the scaffold materials and surfaces.
Poly(dimethyl siloxane) (PDMS) was modified with heparin tethered via a polyethylene oxide (PEO) spacer. For comparison, novel crosslinked collagen scaffolds with covalently incorporated heparin were prepared. Stability of the heparin inside the collagen matrix was assessed. Materials were characterized various techniques including infrared spectroscopy, contact angles, X–ray photoelectron spectroscopy. Heparin density was determined via the toluidine blue assay. HeparinThe modified materials were exposed to varying concentrations of basic fibroblast growth factor (bFGF). The release of the growth factor was measured under physiologically relelvant conditions. Factors affecting growth factor release, including loading pH, loading concentration and the nature of the heparin was examined, as well the interactions of various growth factors with the modified materials.
Surface characterization results indicate PEO and heparin conjugation to the PDMS surfaces. Heparin has been incorporated into collagen gels, both physically and chemically through crosslinking with dendrimers. The collagen materials with a greater degree of chemical crosslinking were found to have significantly more heparin incorporated. Heparin release was observed from the physically crosslinked gels; significantly less heparin spontaneously released when it was chemically immobilized suggesting that physical interactions between the heparin and the collagen were not sufficient to maintain the heparin in the gel. Release of FGF from the various materials has been measured. Initial release results suggest that small amounts of growth factor were released, but more sensitive assay methods are needed to confirm release rates.
PDMS surfaces and collagen materials have been created with immobilized heparin. These materials are able to act as delivery vehicles for soluble growth factors and have potential for improving native host integration with an artificial cornea.
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