Controlled‐release of IGF‐I and TGF‐β1 in a photopolymerizing hydrogel for cartilage tissue engineering

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Abstract
Photopolymerizing hydrogel systems provide a method to encapsulate cells and implant materials in a minimally invasive manner. Controlled release of growth factors in the hydrogels may enhance the ability to engineer tissues. IGF-I and TGF-β were loaded in PLGA microspheres using a double emulsion technique. 125 ng and 200 pg of active IGF-I and TGF-β, respectively, as measured by ELISA, were released over 15 days. The growth factor containing microspheres were photoencapsulated with bovine articular chondrocytes in PEO-based hydrogels and incubated in vitro for two weeks. Statistically significant changes in glycosaminoglycan (GAG) production compared to control gels either without microspheres or with blank spheres were observed after a 14 day incubation with IGF-I and IGF-I/TGF-β microspheres combined, with a maximum density of 8.41 ± 2.5% wet weight GAG. Total collagen density was low and decreased with the IGF-I/TGF-β microspheres after two weeks incubation, but otherwise remained unchanged in all other experimental groups. Cell content increased 10-fold to 0.18 ± 0.056 × 106 cells/mg wet weight and extracellular matrix (ECM) staining by H&E increased in hydrogels with IGF-I/TGF-β microspheres. In conclusion, photoencapsulation of microspheres in PEO-based hydrogels provides a method to deliver molecules such as growth factors in porous hydrogel systems. © 2001 Orthopaedic Research Society. Published by Elsevier Science Ltd. All rights reserved.