title: Protein release kinetics of a biodegradable implant for fracture non-unions.
abstract: Non-union of long bone fractures is often a serious complication of fracture healing. It is estimated that 100 000 non-unions occur in the united States annually and result in the loss of function of the involved limb. The present study was performed to develop a microporous polylactic acid-polyglycolic acid (PLA-PGA) implant for the delivery of bone morphogenetic protein (BMP) to sites of fracture non-unions, and to characterize the protein release kinetics of such an implant in vitro. A 50:50 copolymer of PLA-PGA was used to fabricate the implants using a gel formation technique. The implants were subjected to hydrolytic degradation in phosphate-buffered saline at 37 degrees C for up to 72 d. The protein release and the polymer degradation were monitored during this time period. The release kinetics of these implants were studied using a model protein, soybean trypsin inhibitor (TI), as well as BMP. The results indicate that there is a burst release of the proteins in the initial 48 h followed by a lower elution rate. The release of both the proteins followed similar trends. The molecular weight of the polymer decreased at a faster rate compared to its mass.
authors.affiliation: Department of Orthopaedics, University of Texas Health Science Center at San Antonio 78284, USA.
authors.forename: C M
authors.initials: CM
authors.lastname: Agrawal
authors.forename: J
authors.initials: J
authors.lastname: Best
authors.forename: J D
authors.initials: JD
authors.lastname: Heckman
authors.forename: B D
authors.initials: BD
authors.lastname: Boyan
mesh_terms: D000818:Animals; D001672:Biocompatible Materials; D001673:Biodegradation, Environmental; D019485:Bone Morphogenetic Proteins; D005599:Fractures, Ununited / Q000188:drug therapy*; D066298:In Vitro Techniques; D015918:Infusion Pumps, Implantable; D007700:Kinetics; D019344:Lactic Acid; D008422:Materials Testing; D051379:Mice; D008819:Mice, Nude; D008855:Microscopy, Electron, Scanning; D010012:Osteogenesis / Q000187:drug effects; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers; D011506:Proteins / Q000008:administration & dosage* / Q000493:pharmacokinetics*
chemical_list: D001672:Biocompatible Materials; D019485:Bone Morphogenetic Proteins; D011108:Polymers; D011506:Proteins; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid