title: The preparation of dextran microspheres in an all-aqueous system: effect of the formulation parameters on particle characteristics.
abstract: OBJECTIVE
  The purpose of this study was to investigate the effect of the formulation parameters on the characteristics of dextran-based microspheres, prepared in an all-aqueous system.
  
  
  METHODS
  Dextran microspheres were formed by polymerization of methacryloyl groups attached to dextran (dexMA), emulsified in an aqueous poly(ethylene glycol) (PEG) solution. DexMA/PEG/water phase diagrams were established.
  
  
  RESULTS
  The binodals in the phase diagrams shifted to higher concentrations of dextran and PEG with decreasing molecular weight of both polymers, and with increasing degree of MA substitution. The volume-number mean diameter of the microspheres, varied between 2.5 and 20 microns. For a given formulation, the particle size was independent of the PEG/dexMA volume ratio > 40 and increased for volume ratios < 40. Furthermore, larger particles were obtained with decreasing viscosity of the continuous phase and increasing viscosity of the discontinuous phase.
  
  
  CONCLUSIONS
  Particle characteristics of dextran microspheres prepared in an all-aqueous system, among which the size and initial water content, can be tailored by adjusting the formulation parameters.
authors.affiliation: Department of Pharmaceutics, Utrecht Institute for Pharmaceutical Sciences (UIPS), The Netherlands. R.J.H.Stenekes@far.ruu.nl
authors.forename: R J
authors.initials: RJ
authors.lastname: Stenekes
authors.forename: O
authors.initials: O
authors.lastname: Franssen
authors.forename: E M
authors.initials: EM
authors.lastname: van Bommel
authors.forename: D J
authors.initials: DJ
authors.lastname: Crommelin
authors.forename: W E
authors.initials: WE
authors.lastname: Hennink
mesh_terms: D003911:Dextrans / Q000737:chemistry*; D004337:Drug Carriers; D008863:Microspheres; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry; D013499:Surface Properties; D013816:Thermodynamics; D014783:Viscosity; D014867:Water / Q000737:chemistry*
chemical_list: D003911:Dextrans; D004337:Drug Carriers; D014867:Water; D011092:Polyethylene Glycols