title: New strategy for chemical modification of hyaluronic acid: preparation of functionalized derivatives and their use in the formation of novel biocompatible hydrogels.
abstract: Biodegradable materials for spatially and temporally controlled delivery of bioactive agents such as drugs, growth factors, or cytokines are key to facilitating tissue repair. We have developed a versatile method for chemical crosslinking high-molecular-weight hyaluronic acid under physiological conditions yielding biocompatible and biodegradable hydrogels. The method is based on the introduction of functional groups onto hyaluronic acid by formation of an active ester at the carboxylate of the glucuronic acid moiety and subsequent substitution with a side chain containing a nucleophilic group on one end and a (protected) functional group on the other. We have formed hyaluronic acid with amino or aldehyde functionality, and subsequently hydrogels with these hyaluronic acid derivatives and bifunctional crosslinkers or mixtures of the hyaluronic acid derivatives carrying different functionalities using active ester- or aldehyde-mediated reactions. Size analysis of the hyaluronic acid derivatives showed that the chemical modification did not lead to fragmentation of the polysaccharide. Hydrogels formed with hyaluronic acid derivatized to a varying degree and crosslinked with low- or high-molecular-weight crosslinkers were evaluated for biodegradability by digestion with hyaluronidase and for biocompatibility and ectopic bone formation by subcutaneous implantation in rats. Several hydrogel formulations showed excellent cell infiltration and chondro-osseous differentiation when loaded with bone morphogenetic protein-2 (BMP-2). Synergistic action of insulin-like growth factor-1 with BMP-2 promoted cartilage formation in this model, while addition of transforming growth factor-beta and BMP-2 led to rapid replacement of the matrix by bone.
authors.affiliation: Division of Orthopedic Surgery, University of Wisconsin, H5/301 Clinical Science Center, 600 Highland Avenue, Madison, Wisconsin 53792, USA.
authors.forename: P
authors.initials: P
authors.lastname: Bulpitt
authors.forename: D
authors.initials: D
authors.lastname: Aeschlimann
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects; D019902:Chondrocytes / Q000187:drug effects / Q000473:pathology; D003432:Cross-Linking Reagents; D004357:Drug Synergism; D006820:Hyaluronic Acid / Q000737:chemistry / Q000494:pharmacology; D051381:Rats; D016212:Transforming Growth Factor beta
chemical_list: D001672:Biocompatible Materials; C525720:Bmp2 protein, rat; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D003432:Cross-Linking Reagents; D016212:Transforming Growth Factor beta; D006820:Hyaluronic Acid