Low-energy nano-emulsification approach as a simple strategy to prepare positively charged ethylcellulose nanoparticles

Abstract

Positively charged ethylcelulose nanoparticles have been obtained from alkylamidoammonium/Span 80 based nano-emulsion templates. Oil-in-water polymeric nano-emulsions form in a broad range of oil-to-surfactant ratios and water contents above 75 wt% by a low-energy method at 25 °C. Nano-emulsions with a water content of 90 wt% showed droplet sizes typically below 300 nm and high positive zeta potential values (∼55 mV). If oleylamine is added to the system, smaller droplet sizes and higher zeta potential values (∼66 mV) are obtained, but the stability of the nano-emulsions decreases. Although these nano-emulsions are destabilized by creaming, the period of stability is large enough to allow nanoparticle preparation by solvent evaporation. Polymeric nanoparticles obtained show a globular core-shell-like morphology, with mean diameters of around 250 nm. The surface charge of the nanoparticles is similar to that of the nano-emulsion template and remains positive after 24 h dialysis, suggesting slow desorption kinetics of the alkylamidoammonium from the nanoparticle surface. These results indicate that the proposed nano-emulsion approach is a good strategy for the preparation of positively charged nanoparticles from nonionic ethylcellulose polymers.