title: An investigation into the effects of residual water on the glass transition temperature of polylactide microspheres using modulated temperature DSC.
abstract: The objective of the study was to ascertain residual water levels in polylactide and polylactide-co-glycolide microspheres prepared using the solvent evaporation technique and to investigate the effects of that water on the glass transitional behaviour of the microspheres. Microspheres were prepared from polylactic acid (PLA) and polylactide-co-glycolide (PLGA) 50:50 and 75:25 using a standard solvent evaporation technique. The glass transition was measured as a function of drying conditions using modulated temperature DSC. The microspheres were found to contain very low levels of dichloromethane, while residual water levels of up to circa 3% w/w were noted after freeze or oven drying, these levels being higher for microspheres containing higher glycolic acid levels. The residual water was found to lower the T(g) following the Gordon-Taylor relationship. The data indicate that the microparticles may retain significant water levels following standard preparation and drying protocols and that this drying may markedly lower the T(g) of the spheres.
authors.affiliation: The School of Pharmacy, The Queen's University of Belfast, Biomedical Centre, 97 Lisburn Road, BT9 7BL, Belfast, UK.
authors.forename: N
authors.initials: N
authors.lastname: Passerini
authors.forename: D Q
authors.initials: DQ
authors.lastname: Craig
mesh_terms: D002152:Calorimetry, Differential Scanning; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D003890:Desiccation; D004337:Drug Carriers / Q000737:chemistry*; D005612:Freeze Drying; D019344:Lactic Acid / Q000737:chemistry*; D008863:Microspheres; D011091:Polyesters / Q000737:chemistry*; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D014867:Water / Q000737:chemistry
chemical_list: D004337:Drug Carriers; D011091:Polyesters; D011108:Polymers; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; C033616:poly(lactide)