title: Development of biodegradable poly(propylene fumarate)/poly(lactic-co-glycolic acid) blend microspheres. II. Controlled drug release and microsphere degradation.
abstract: This article describes the effects of six processing parameters on the release kinetics of a model drug Texas red dextran (TRD) from poly(propylene fumarate)/poly(lactic-co-glycolic acid) (PPF/PLGA) blend microspheres as well as the degradation of these microspheres. The microspheres were fabricated using a double emulsion-solvent extraction technique in which the following six parameters were varied: PPF/PLGA ratio, polymer viscosity, vortex speed during emulsification, amount of internal aqueous phase, use of poly(vinyl alcohol) in the internal aqueous phase, and poly(vinyl alcohol) concentration in the external aqueous phase. We have previously characterized these microspheres in terms of microsphere morphology, size distribution, and TRD entrapment efficiency. In this work, the TRD release profiles in phosphate-buffered saline were determined and all formulations showed an initial burst release in the first 2 days followed by a decreased sustained release over a 38-day period. The initial burst release varied from 5.1 (+/-1.1) to 67.7 (+/-3.4)% of the entrapped TRD, and was affected most by the viscosity of the polymer solution used for microsphere fabrication. The sustained release between day 2 and day 38 ranged from 7.9 (+/-0.8) to 27.2 (+/-3.1)% of the entrapped TRD. During 11 weeks of in vitro degradation, the mass of the microspheres remained relatively constant for the first 3 weeks after which it decreased dramatically, whereas the molecular weight of the polymers decreased immediately upon placement in phosphate-buffered saline. Increasing the PPF content in the PPF/PLGA blend resulted in slower microsphere degradation. Overall, this study provides further understanding of the effects of various processing parameters on the release kinetics from PPF/PLGA blend microspheres thus allowing modulation of drug release to achieve a wide spectrum of release profiles.
authors.affiliation: Tissue Engineering & Polymeric Biomaterials Laboratory, Department of Orthopedic Surgery, Mayo Clinic, 200 First Street SW, Rochester, Minnesota 55905.
authors.forename: Diederik H R
authors.initials: DH
authors.lastname: Kempen
authors.forename: Lichun
authors.initials: L
authors.lastname: Lu
authors.forename: Xun
authors.initials: X
authors.lastname: Zhu
authors.forename: Choll
authors.initials: C
authors.lastname: Kim
authors.forename: Esmaiel
authors.initials: E
authors.lastname: Jabbari
authors.forename: Wouter J A
authors.initials: WJ
authors.lastname: Dhert
authors.forename: Bradford L
authors.initials: BL
authors.lastname: Currier
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Yaszemski
mesh_terms: D001672:Biocompatible Materials / Q000302:isolation & purification*; D001673:Biodegradation, Environmental; D003692:Delayed-Action Preparations; D003911:Dextrans / Q000008:administration & dosage / Q000493:pharmacokinetics; D016503:Drug Delivery Systems; D004655:Emulsions; D005650:Fumarates / Q000302:isolation & purification*; D006016:Glycolates / Q000302:isolation & purification*; D066298:In Vitro Techniques; D019344:Lactic Acid; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D010316:Particle Size; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011126:Polypropylenes / Q000302:isolation & purification*; D013499:Surface Properties; D014783:Viscosity; D014867:Water; D014966:Xanthenes / Q000008:administration & dosage / Q000493:pharmacokinetics
chemical_list: D001672:Biocompatible Materials; D003692:Delayed-Action Preparations; D003911:Dextrans; D004655:Emulsions; D005650:Fumarates; D006016:Glycolates; D011126:Polypropylenes; D014966:Xanthenes; C097850:poly(propylene fumarate); D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C034657:Texas red