The preparation of dextran microspheres in an all-aqueous system: Effect of the formulation parameters on particle characteristics

Purpose. 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 mu m. 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.