Nanoparticle formation of organic compounds with retained biological activity.

Many pharmaceuticals are formulated as powders to aid drug delivery. A major problem is how to produce powders having high purity, controlled morphology, and retained bioactivity. We demonstrate the use of supercritical carbon dioxide as an antisolvent for meeting this need for two model drug systems, quercetin, a sparingly soluble antioxidant, and short interfering RNA (siRNA), which can silence genes. In both cases we achieve retention of bioactivity as well as a narrow particle size distribution in which the particles are free of impurities.