title: The influence of surfactant on PLGA microsphere glass transition and water sorption: remodeling the surface morphology to attenuate the burst release.
abstract: OBJECTIVE
  The stability of protein unloaded and loaded poly(lactic-co-glycolic acid) (PLGA) microspheres fabricated with surfactant was challenged through exposure to environmental conditions of different relative humidity.
  
  
  METHODS
  Polyvinyl alcohol (PVA) or Triton X-100 was added to the primary emulsion of the double-emulsion solvent evaporation technique. After storage at ambient humidity and 75% relative humidity, the mechanical stability of the polymer was tested to reveal PLGA chain mobility using differential scanning calorimetry. Subsequent surface modifications were examined by atomic force microscopy (AFM), and protein release profiles were collected.
  
  
  RESULTS
  Residual amounts of PVA and particularly Triton X-100 raised the hydrophilicity of the microspheres. When exposed to ambient humidity or 75% relative humidity, PVA and Triton X-100 had, respectively, an antiplasticizing and a plasticizing effect upon PLGA, and both led to physical aging. The high-resolution AFM imaging of microspheres containing model protein and Triton X-100 showed that the depth of the surface pores was reduced when exposed to 75% relative humidity, and the initial burst release subsequently decreased.
  
  
  CONCLUSIONS
  These studies suggested that the mechanical stability of PLGA was influenced by the addition of surfactants, which, depending on the formulation, led to surface pore remodeling under high humidity, reducing the initial burst release while maintaining the spherical integrity of the microsphere.
authors.affiliation: Department of Pharmacy, University of Bath, Bath, BA2 7AY, UK.
authors.forename: C
authors.initials: C
authors.lastname: Bouissou
authors.forename: J J
authors.initials: JJ
authors.lastname: Rouse
authors.forename: R
authors.initials: R
authors.lastname: Price
authors.forename: C F
authors.initials: CF
authors.lastname: van der Walle
mesh_terms: D003692:Delayed-Action Preparations; D004337:Drug Carriers; D004339:Drug Compounding; D005353:Fibronectins / Q000737:chemistry*; D006813:Humidity; D019344:Lactic Acid / Q000737:chemistry*; D008863:Microspheres; D017830:Octoxynol / Q000737:chemistry; D010316:Particle Size; D011100:Polyglycolic Acid / Q000737:chemistry*; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D011142:Polyvinyl Alcohol / Q000737:chemistry; D016062:Porosity; D012995:Solubility; D013499:Surface Properties; D013501:Surface-Active Agents / Q000737:chemistry*; D013997:Time Factors; D044366:Transition Temperature; D014867:Water / Q000737:chemistry*
chemical_list: D003692:Delayed-Action Preparations; D004337:Drug Carriers; D005353:Fibronectins; D011108:Polymers; D013501:Surface-Active Agents; D014867:Water; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D011142:Polyvinyl Alcohol; D017830:Octoxynol