title: Recombinant human bone morphogenetic protein-2 binding and incorporation in PLGA microsphere delivery systems.
abstract: The objective of this research was to determine the binding capacity and kinetics, and total incorporation of recombinant human bone morphogenetic protein-2 (rhBMP-2) in microspheres made from hydrophilic and hydrophobic poly(lactide-co-glycolide) (PLGA). Polymers were characterized by molecular weight, polydispersity, and acid number. Microspheres were produced via a water-in-oil-in-water double emulsion system and characterized for bulk density, size, specific surface area, and porosity. Protein concentrations were determined by reversed phase HPLC. Protein was loaded by soaking microspheres in a buffered solution, pH 4.5, of rhBMP-2, decanting excess liquid, and vacuum drying the wetted particles. Total loading and binding were determined by comparing protein concentration remaining to non-microsphere containing samples. Polymer acid number was the dominant polymer feature affecting the binding. Higher acid values correlated with increased rhBMP-2 binding. The amount of non-bound incorporated rhBMP-2 linearly correlated with the concentration of protein used in binding. High rhBMP-2 concentrations inhibit binding to PLGA microspheres. Binding was also inhibited by increased lactide content in the PLGA polymer. The polymer characteristics controlling rhBMP-2 binding to PLGA microspheres are acid value foremost followed by molecular weight and lactide/glycolide ratio. The total amount of rhBMP-2 incorporated depends on the bound amount and on the amount of free protein present.
authors.affiliation: Cabrillo Laboratories, San Diego, California 92126, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Schrier
authors.forename: P P
authors.initials: PP
authors.lastname: DeLuca
mesh_terms: D000327:Adsorption; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000008:administration & dosage / Q000737:chemistry*; D002850:Chromatography, Gel; D016503:Drug Delivery Systems; D005079:Excipients / Q000737:chemistry*; D005612:Freeze Drying; D006801:Humans; D007700:Kinetics; D019344:Lactic Acid / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D016062:Porosity; D011485:Protein Binding; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000737:chemistry; D016212:Transforming Growth Factor beta / Q000737:chemistry*
chemical_list: C525718:BMP2 protein, human; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D005079:Excipients; D011108:Polymers; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid