Self-organized drug-interpolyelectrolyte nanocomplexes loaded with anionic drugs. Characterization and in vitro release evaluation

The current study is focused on physicochemical characterization and in vitro drug delivery evaluation of self-organized nanoparticles based on drug-interpolyelectrolyte complexes (DIPEC). The interaction between two oppositely charged polymethacrylates, Eudragit® EPO and L100, and four non-steroidal anti-inflammatory drugs, Salicylic Acid, Benzoic Acid, Ketoprofen and Naproxen was studied.DIPEC nanoparticles produce translucent and stable aqueous dispersions where a remarkably high proportion of drug (between 57 and 95%) is condensed with polyelectrolyte (PE) under the form of ionic pairs. They exhibited particle size in the range of 120–198 nm and high positive zeta potential, contributing to physical stability. The sign of zeta potential shifted from positive to negative by changes in composition of DIPEC. Thermal analysis and X-ray diffraction patterns of freeze dried DIPEC showed the amorphous state of products and the complete interaction of PE and drug. Solid complexes were easily redispersed in water yielding nearly the same parameters of fresh dispersions. In vitro release experiments showed that DIPEC nanodispersions behave as drug reservoirs, exhibiting a slow drug release rate in water, which significantly increased in simulating physiological fluids, promoted by ionic exchange. They also exhibited a remarkable robustness towards simulated physiological media of different pH.

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