Recent advances in the preparation of drug delivery systems using supercritical fluid technologies

The most significant challenge that the pharmaceutical field is currently facing is the low bioavailability of the drugs, mostly due to their poor aqueous solubility and dissolution rates. The supercritical fluid (SCF) technology is an environmentally-friendly alternative to conventional techniques for preparing drug delivery systems, which can tremendously improve the bioavailability of the drugs and protect them from hard conditions such as temperature, oxygen and pH, so enhancing their stability. The tunable properties of the supercritical fluids allow the SCF technologies to produce modified final products, based on the desired application. The supercritical CO2 is the most used SCF, due to its mild supercritical conditions, inexpensiveness, chemical stability, non-flammability, and non-toxicity. The aim of this work is to provide a general overview of the main drug delivery systems prepared by SCF technology, with a special focus on those prepared in the last five years. The drug delivery systems here discussed are polymer micro- and nanoparticles, aerogels, microporous foams, liposomes, solid lipid nanoparticles, as well as those prepared with the supercritical impregnation technique. By analyzing the recent advances of the above-mentioned drug delivery systems, some conclusions are reported, and some future perspectives are proposed.