title: POE/PLGA composite microspheres: formation and in vitro behavior of double walled microspheres.
abstract: The poly(ortho ester) (POE) and poly(D,L-lactide-co-glycolide) 50:50 (PLGA) composite microspheres were fabricated by a water-in-oil-in-water (w/o/w) double emulsion process. The morphology of the composite microspheres varied depending on POE content. When the POE content was 50, 60 or 70% in weight, the double walled microspheres with a dense core of POE and a porous shell of PLGA were formed. The formation of the double walled POE/PLGA microspheres was analysed. Their in vitro degradation behavior was characterized by scanning electron microscopy, gel permeation chromatography, Fourier-transform infrared microscopy and nuclear magnetic resonance spectroscopy (NMR). It was found that compared to the neat POE or PLGA microspheres, distinct degradation mechanism was achieved in the double walled POE/PLGA microspheres system. The degradation of the POE core was accelerated due to the acidic microenvironment produced by the hydrolysis of the outer PLGA layer. The formation of hollow microspheres became pronounced after the first week in vitro. 1H NMR spectra showed that the POE core was completely degraded after 4 weeks. On the other hand, the outer PLGA layer experienced slightly retarded degradation after the POE core disappeared. PLGA in the double walled microspheres kept more than 32% of its initial molecular weight over a period of 7 weeks.
authors.affiliation: Institute of Materials Research and Engineering, No. 3 Research Link, Singapore 117602, Singapore. yy-yang@imre.org.sg
authors.forename: Yi-Yan
authors.initials: YY
authors.lastname: Yang
authors.forename: Meng
authors.initials: M
authors.lastname: Shi
authors.forename: Suat-Hong
authors.initials: SH
authors.lastname: Goh
authors.forename: Shabbir M
authors.initials: SM
authors.lastname: Moochhala
authors.forename: Steve
authors.initials: S
authors.lastname: Ng
authors.forename: Jorge
authors.initials: J
authors.lastname: Heller
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004339:Drug Compounding; D019344:Lactic Acid / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008855:Microscopy, Electron, Scanning; D008863:Microspheres; D008970:Molecular Weight; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D011108:Polymers; C401107:poly(ortho ester); D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid