Influence of process parameters of high-pressure emulsification method on the properties of pilocarpine-loaded nanoparticles.

Poly(lactide-co-glycolide) nanoparticles loaded with pilocarpine hydrochloride were prepared by the high-pressure emulsification-solvent evaporation method. The nanoparticles were produced using polyvinylalcohol (PVA), carbomer (Carbopol 980) or poloxamer (Lutrol F-68) as stabilizers during emulsification. The influence of pressure and number of cycles on the nanoparticle properties was investigated. For comparison, nanoparicles without high-pressure treatment of the emulsion were made. The nanoparticle size, drug loading and release properties depended strongly on the homogenization pressure and number of cycles applied. Nanoparticles obtained without high pressure homogenization showed larger size and high values of polydispersity index, especially when carbopol and poloxamer were used as emulsifiers. Drug loading and encapsulation efficiency of all samples also decreased with pressure. The low drug loading could be due to two reasons. First, the high pressure promoted drug diffusion out of protoparticles during emulsification either by size reduction or shear forces. Secondly, the characteristics of the outer water phase of the emulsion also influenced the nanoparticle drug loading. This was proven by the different drug loadings measured when nanoparticles were made with PVA, carbopol or poloxamer at equal pressures applied. The main factor influencing the release properties of nanoparticles was the pressure used during emulsification. Faster drug release was observed from nanoparticles obtained after high-pressure emulsification compared to those prepared without homogenization of the emulsion.