title: In situ apatite forming injectable hydrogel.
abstract: Injectable polymers are attractive materials for tissue augmentation or replacement. Thermosensitive hydrogels, especially poly(N-isopropylacryamide), have been investigated for these applications to exploit the lower critical solution temperature (LCST) which falls between room and body temperatures. Some practical limitations to the material are the load-bearing capabilities and the ability to bond to the host tissue. In this work, we evaluated a novel, injectable apatite-forming material system: poly(N-isopropylacryamide)-co-poly(ethyleneglycol) dimethacrylate, with the addition of tri-methacryloxypropyltrimethoxysilane (MPS). We have previously reported that MPS concentration permits the material system to be tuned to different compressive moduli ranging from 50-700 kPa without altering the LCST of the material. Here, we explore the apatite formation of this material system in protein-free and protein-containing SBF. The MPS-containing hydrogel system exhibited apatite formation throughout the gel thickness. The apatite formation was inhibited by the presence of proteins. This mechanism is likely controlled by the silanol groups (Si-OH) in MPS, which provided attachment sites for calcium and initiated mineral dissolution from the simulated biological environments. The challenge of this material system is to balance the network-forming and modulus-enhancing MPS while maintaining an injectable hydrogel for potential tissue regeneration.
authors.affiliation: Department of Materials Science and Engineering, College of Engineering, Drexel University,3201 Chestnut Street, Philadelphia, Pennsylvania 19104,USA.
authors.forename: Emily
authors.initials: E
authors.lastname: Ho
authors.forename: Anthony
authors.initials: A
authors.lastname: Lowman
authors.forename: Michele
authors.initials: M
authors.lastname: Marcolongo
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D001031:Apatites / Q000737:chemistry*; D001826:Body Fluids; D004548:Elasticity; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate / Q000737:chemistry*; D007267:Injections; D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D011092:Polyethylene Glycols / Q000737:chemistry; D012821:Silanes / Q000737:chemistry; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D000180:Acrylic Resins; D001031:Apatites; D008689:Methacrylates; D012821:Silanes; C421283:poly(ethylene glycol)-dimethacrylate; C052970:poly-N-isopropylacrylamide; C017492:methacryloxypropyltrimethoxysilane; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D011092:Polyethylene Glycols