Gelatin nanoparticle preparation by nanoprecipitation.

This study focuses on the novel preparation of gelatin nanoparticles by nanoprecipitation. The principal parameters studied for its optimum conditions were the concentration of emulsifier, the time of emulsifier addition, the concentration of gelatin in solvent phase and the non-solvent volume. In addition, the effect of type of non-solvent (ethanol, n-propanol, methanol) was also studied. It was notable that emulsifier should exist in the non-solvent phase to prevent aggregation of gelatin nanoparticles prepared by nanoprecipitation. The emulsifier to gelatin mass ratio of 32:1 was found to be appropriate to fabricate stable nanoparticles without inter-particle aggregation caused by charge neutralization, during the course of cross-linking. The yield of gelatin nanoparticles was calculated gravimetrically after freeze drying. The freeze-dried nanoparticles were characterized for size and morphology by scanning electron microscopy. The division between nanoparticles was found most clear and vivid in the freeze-drying-induced matrix, owing to the least inter-particle aggregation during the process of cross-linking, for the case of 2% (w/v) emulsifier. The morphology of the freeze-dried nanoparticles turned out to be a spherical or hexagonal regular shape with a smooth surface in the freeze-drying-induced matrix. Their number-mean size is barely 115 nm and their unimodal size-mean is 215 nm with an unimodal polydispersity of 0.1547, the former of which is much smaller and the latter belongs to the lower limit of the gelatin nanoparticle size of 200-500 nm prepared by the coacervation method. Thus, as far as the morphology and the size of prepared gelatin nanoparticles are concerned, the optimum conditions may be derived from those of the above-mentioned morphology. The comparative experiments performed using the coacervation method turned out to require stirring and the nanoparticles still exhibited stability problems, even in the presence of emulsifier. Therefore, the results presented in this study show the optimum conditions and reflect the unexploited potential of the nanoprecipitation method for the preparation of nanoparticles from hydrophilic polymers like gelatin.