Ibuprofen-loaded nanoparticles prepared by a co-precipitation method and their release properties.

A co-precipitation method was established to fabricate nano-scale core-shell particles, by which poor water-soluble drugs can be effectively dispersed with rather good stability during storage. Exemplified with formation of ibuprofen (Ib) nanoparticles stabilized by DEAE dextran (Ddex), the process includes precipitation of Ib in a supersaturated solution and deposition of Ddex onto the precipitated Ib particles through electrostatic interaction. Characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), dynamic light scattering (DLS) and zeta potential, the core-shell structure of the particles formed at pH 6.0 with a Ddex/Ib weight ratio of 5:1 was identified with Ib being the core and Ddex being the shell. As a comparison, particles formed at other pH values and other Ddex/Ib ratios were also studied. Along with increase of the Ddex/Ib ratio or pH value of the final aqueous solution, the particle size was decreased, demonstrating that the particle sizes could be readily tuned by variation of the fabrication parameters. At conditions that the Ib concentration was lower than its supersaturated value, for example at higher pH value, instead of co-precipitation mechanism, forces such as electrostatic complexation dominate the formation of Ddex-Ib particles. Moreover, drug entrapment was mainly dependent on the Ib solubility regardless of the ratio between Ddex and Ib, while the drug content was decreased as a function of Ddex/Ib ratio. In vitro release studies showed that the loaded Ib could be again released in a burst manner during the initial stage, followed with a slow rate. The final released amount of Ib showed a positive correlation with the bulk pH value, e.g. approximately 60, 80 and 90% of the loaded Ib were released in pH 1.0, 5.8 and 7.4 buffered solutions after incubation for 40 h, respectively.