A Coat of Many Layers

Abstract

DRUG DELIVERY Several particle-coating methods have been developed for time-released drug delivery, but few have been tested under in vivo conditions. Recently, two groups have subjected their delivery systems to some of these conditions. Qui et al. encapsulated micrometer-sized ibuprofen crystals through repeated adsorption of oppositely charged biocompatible polysaccharides. The polymer coating delayed ibuprofen release at pH 1.4 (representative of gastric fluid) but did not significantly affect release at pH 7.4 (similar to intestinal pH). Marinakos et al. used gold colloidal particles to support small molecules or enzymes. Conductive polymer coatings were formed in situ without altering the biomolecules, and then the colloidal core was dissolved away. The addition of counterions was shown to influence the diffusion rate of the encapsulated small molecules, and coated enzymes showed greater resistance to harsh solvents. When generated in this fashion, poly(pyrrole) capsules 25 to 100 nm in diameter were absorbed by mouse fibroblasts without compromising cell viability. — MSL Langmuir , 10.1021/la010201w; J. Phys. Chem. B . 10.1021/jp010820d.