Polymeric-nanoparticle systems such as nanocapsules and nanospheres have a great potential in applications for nanoencapsulation of corticosteroids which show low solubility in water. The physicochemical characteristics of nanoparticle suspensions are important pre-requisites for the successful development of new dosage form. In this study, hydrocortisone-loaded poly-ε-caprolactone nanoparticles have been prepared by the interfacial deposition method. A 3-factor 2-level factorial design was used to study and optimize nanoparticles formulation. This factorial design was used to study the contrasts and effects of independent variables on particle size distribution, morphology, surface charge, drug content, entrapment efficiency and in vitro drug release profiles. The screened independent variables were: the concentration of hydrocortisone, poly-ε-caprolactone and isodecyl oleate. A High Performance Liquid Chromatography method was developed and validated for hydrocortisone quantification. Special attention was given to both absolute recovery and entrapment efficiency. The results of optimized formulations showed a narrow size distribution with a polydispersity index near to 0.200. The particle sizes were on average 109.2 and 236.5nm to nanospheres and nanocapsules, respectively. In the best formulations the zeta potential was higher than 30 mV (in module) and the absolute recovery and entrapment efficiency were higher 82% and nearly 60%, respectively. The main variables were the quantity of the polymer and of the oil. Nanoparticles observed by the Scanning Electron Microscope depicted extremely spherical shape. In vitro release studies were performed through dialysis with continuous stream. Nanocapsules and nanospheres showed a similar pure diffusion release mechanism according to Korsmeyer-Peppas’s model.
