PLGA particle production for water soluble drug encapsulation: degradation and release behaviour

Particles for subcutaneous depot use encapsulating a model water soluble drug have been produced from poly(lactic-glycolic acid) (PLGA) using a membrane emulsification – solvent evaporation technique. The release behaviour, mainly the change in size and inner morphology are reported. During release, the particles initially swelled in size, then reduced. A diffusion based model, taking in to account the change in particle size, is presented. Surface erosion is evident from the particle size and image evidence, and the diffusion model provides a fit to the data even during the surface erosion period, suggesting that the model drug diffuses before the particle degrades.