On Single Step Assembly of Uniform Core-Shell Microparticles with Tunable Controlled Release Functionalities

Core/shell microparticles are of interest for various applications including pharmaceutical engineering, due to the possibility of fine-tuning individual functionalities of the different parts. Here we report a new approach for continuous and scalable production of core/shell microparticles, using acrylic nanoparticles (Eudragit¨ RS) as the shell, and hydrolized tetraethyl orthosilicate (TEOS) forming the silica core upon the single-step assembly. The method is capable of forming monodisperse microparticles from homogeneous precursors without the use of any organic solvents. Precise control of particle uniformity is realized via the use of a micro-fluidic spray drying technique, which has been previously demonstrated to generate monodisperse chitosan microparticles of specific sizes [1] and polymeric microparticles for controlled drug release applications [2]. Evaporation induced self-assembly during spray drying is utilized to manipulate the spatial configuration of the particles, including shell thickness. Control over the shell thickness can be directly achieved from the ratio of ingredients in the precursors. A fluorescent compound, Rhodamine B, is used as a highly water-soluble model drug to investigate the controlled release properties of these microparticles, with the release behaviors shown to be significantly dependent on the microstructural properties.

A schematic diagram of particle formation due to evaporation induced self-assembly during spray drying, with FESEM images of (A) monodisperse spray dried microparticles with average diameter of 55 mm, with (B) cross-section displaying core-shell configuration (inset scale bar: 1µm).

References:

1.    Liu, W., Wu, W., Selomulya, C., Chen, X. D., 2011, Uniform Chitosan Microparticles Prepared by a Novel Spray-Drying Technique, International Journal of Chemical Engineering, doi:10.1155/2011/267218

2.    Liu, W., Wu, W., Selomulya, C., Chen, X. D., 2011, A single step assembly of uniform microparticles for controlled release applications, Soft Matter, DOI:10.1039/C0SM01371D.