Modulating size and surface charge of ethylcellulose nanoparticles through the use of cationic nano-emulsion templates.

Ethylcellulose nano-emulsions have been obtained by the low-energy phase inversion composition method in the Water / [Alkylamidoammonium: Cremophor WO7] / [6% ethylcellulose in ethyl acetate] system at 25 °C. It is shown that nano-emlulsions' composition variables (oil-to-surfactant ratio, cationic: nonionic surfactant ratio and polymer and water content) produce changes in their droplet diameter, surface charge and colloidal stability following defined trends. Nano-emulsions with good stability, droplet diameters between about 120 and 200 nm and surface charge from about 10 to 50 mV have been obtained. Nano-emulsions are further used as templates for nanoparticle dispersions preparation, which show sizes and surface charges typically smaller and similar respectively to their nano-emulsion templates. Cationic: nonionic surfactant ratio has the highest influence on both, size and surface charge, followed by oil-to-surfactant ratio and water content. Interestingly, the positive charge of the nanoparticles can be depleted under diluting conditions in a time-dependent manner.