title: Hydrophilic polyester microspheres: effect of molecular weight and copolymer composition on release of BSA.
abstract: OBJECTIVE
  To study the release of a model protein, bovine serum albumin (BSA), from microspheres of an hydroxylated aliphatic polyester, poly(lactic-co-hydroxymethyl glycolic acid) (PLHMGA).
  
  
  METHODS
  BSA-loaded microspheres were prepared by a double emulsion solvent evaporation method. The effect of copolymer composition and the molecular weight of the copolymer on in vitro release and degradation were studied. The integrity of the released BSA was studied by fluorescence spectroscopy and size exclusion chromatography (SEC).
  
  
  RESULTS
  Microspheres prepared from PLHMGA with 50% hydroxymethyl glycolic acid (HMG) showed a burst release followed by a sustained release in 5-10 days. PLHMGA microspheres prepared from a copolymer with 35% and 25% HMG showed a sustained release of BSA up to 80% for 30 and 60 days, respectively. The release of BSA was hardly affected by the molecular weight of the polymer. Fluorescence spectroscopy and SEC showed that the released BSA preserved its structural integrity. Microspheres were fully degradable, and the degradation time increased from approximately 20 days to 60 days when the HMG content decreased from 50% to 25%.
  
  
  CONCLUSIONS
  Taking the degradation and release data together, it can be concluded that the release of BSA from PLHMGA microspheres is governed by degradation of the microspheres.
authors.affiliation: Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), Utrecht University, P.O. Box 80082, Sorbonnelaan 16, 3508 TB, Utrecht, The Netherlands.
authors.forename: Amir H
authors.initials: AH
authors.lastname: Ghassemi
authors.forename: Mies J
authors.initials: MJ
authors.lastname: van Steenbergen
authors.forename: Herre
authors.initials: H
authors.lastname: Talsma
authors.forename: Cornelus F
authors.initials: CF
authors.lastname: van Nostrum
authors.forename: Daan J A
authors.initials: DJ
authors.lastname: Crommelin
authors.forename: Wim E
authors.initials: WE
authors.lastname: Hennink
mesh_terms: D002850:Chromatography, Gel; D004337:Drug Carriers / Q000737:chemistry*; D004339:Drug Compounding; D006900:Hydroxylation; D008863:Microspheres; D015394:Molecular Structure; D008970:Molecular Weight; D010316:Particle Size; D011091:Polyesters / Q000737:chemistry*; D055550:Protein Stability; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012995:Solubility; D013050:Spectrometry, Fluorescence
chemical_list: D004337:Drug Carriers; D011091:Polyesters; C544675:poly(lactic-co-hydroxymethyl glycolic acid); D012710:Serum Albumin, Bovine