title: Evaluation of the degradation of clonidine-loaded PLGA microspheres.
abstract: BACKGROUND
  The release of an encapsulated drug is dependent on diffusion and/or degradation/erosion processes.
  
  
  OBJECTIVE
  This work aimed to better understand the degradation mechanism of clonidine-loaded microparticles.
  
  
  METHODS
  Gel permeation chromatography was used to evaluate the degradation of the polymer. The water-uptake and the weight loss were determined gravimetrically. The swelling behaviour and the morphological changes of the formulations were observed by microscopy. The glass transition temperature and the crystallinity were also determined by differential scanning calorimetry and X-ray diffraction, respectively. The pH of the medium and inside the microspheres was assessed.
  
  
  RESULTS
  The microspheres captured a large amount of water, allowing a decrease in the molecular weight of the polymer. The pH of the medium decreased after release of the degradation products and the pH inside the microparticles remained constant due to the neutralization of these acidic products.
  
  
  CONCLUSIONS
  Clonidine and buffers both had an action on the degradation.
authors.affiliation: Laboratory of Pharmaceutics and Biopharmaceutics, Université Libre de Bruxelles , City of Brussels , Belgium.
authors.forename: Amélie
authors.initials: A
authors.lastname: Gaignaux
authors.forename: Jonathan
authors.initials: J
authors.lastname: Réeff
authors.forename: Carine
authors.initials: C
authors.lastname: De Vriese
authors.forename: Jonathan
authors.initials: J
authors.lastname: Goole
authors.forename: Karim
authors.initials: K
authors.lastname: Amighi
mesh_terms: D000700:Analgesics / Q000008:administration & dosage*; D002021:Buffers; D003000:Clonidine / Q000008:administration & dosage*; D004337:Drug Carriers / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000737:chemistry*; D008863:Microspheres; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D044366:Transition Temperature; D014961:X-Ray Diffraction
chemical_list: D000700:Analgesics; D002021:Buffers; D004337:Drug Carriers; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D003000:Clonidine