A supercritical fluid-based coating technology 1: process considerations

A novel solvent-free particle coating process, based on the solvent properties of supercritical fluids (SCF) is described. It consists of dissolving one or more coating materials in supercritical CO(2) and then adjusting T/P conditions in the autoclave so that the coating material becomes insoluble in the CO(2). This insolubilization step causes a coating to deposit on the surface of suspended particles. This process has been applied to bovine serum albumin and sugar granules. Coating was effective, but different morphologies were obtained depending on the coating material used. A discontinuous coating has been made using trimyristin, since this material precipitates as micro-needles. Conversely, a smooth, regular coating has been obtained with a commercially available mixture of glycerides and glyceride esters of PEG (Gelucire 50/02) acting like a film-forming agent.