Influence of polymer concentration on the properties of nano-emulsions and nanoparticles obtained by a low-energy method

Abstract

This study concerns the effect of polymer content on the properties of nano-emulsions formulated by the PIC low-energy method and on the nanoparticles prepared from nano-emulsions by solvent evaporation. The region of nano-emulsion formation, droplet size and stability as a function of polymer content were investigated. Nano-emulsions were formed in a wide range of oil-to-surfactant weight ratios (Ros) and water contents higher than 45%. For nanoparticles, droplet size, stability, encapsulation efficiency, pH, drug release and cytotoxicity effect were evaluated as a function of polymer content. Nano-emulsion droplet size (Rh=8–75nm) and nanoparticle size (Rh=8–55nm) increase with the polymer content. No desestabilization process such as creaming or sedimentation was observed by light transmittance/backscattering neither in nano-emulsions nor in nanoparticle dispersions. The morphology and size of nano-emulsions and nanoparticles were comfirmed by Cryo-TEM and TEM techniques, respectively. The pH of nanoparticle dispersions was in the range of 5–6.5 during the studied experimental time (7days), an indication of no polymer degradation. Moreover, Dexamethasone (DXM) encapsulated in the polymeric nanoparticles (0.18wt% DXM in the oil phase of the template nano-emulsion) did not modify the nanoparticle size. No effect of polymer concentration was found in the encapsulation efficiency (close to 90%) of DXM. In vitro drug release studies indicated Fick’s diffusion as the main drug release mechanism from the nanoparticle to the receptor solution. DXM loaded and non-loaded nanoparticles showed cell viability higher than 70%. This study reports a promising system to be used as template for polymeric nanoparticle preparation suitable for biomedical applications.