Drug dissolution chip (DDC): a microfluidic approach for drug release.

DOI: 10.1002/smll.201100520 The effectiveness of drug delivery relies on the drug being released from its pharmaceutical dosage form, such as a tablet or capsule, and dissolving in body fl uids prior to absorption, and transport to the therapeutic target. [ 1 ] The analytical investigation of drug release from its dosage form is called dissolution testing and is essential in development as well as in manufacturing and quality control of pharmaceutical dosage forms. [ 2 ] The fundamental methodology of dissolution testing entails a defi ned amount of the dosage form immersed in a predetermined volume of dissolution medium. The concentration of the released drug in the medium is measured in distinct time intervals, yielding time-dependant dissolution profi les. The compartment containing the dosage form is typically a vessel or chamber equipped with mechanical barriers, such as fi lters or a bed of glass beads, which retain the solid sample. The dissolution medium is pumped through this compartment at a constant fl ow rate, and the drug concentration in the dissolution medium is determined with highperformance liquid chromatography or UV–vis spectroscopy. Unfortunately, the drug can undergo changes in its solid state which can have marked effects on its dissolution rate. [ 3 , 4 ]