High-throughput screening of xanthine oxidase inhibitory properties of drug analogs using photodiode array microchip

We have developed a high-throughput chip-based assay that uses a photodiode array (PDA) microchip system to explore the inhibitory effects of drug analogs on Xanthine oxidase (XO). Inhibitory effects of dithranol (anthracene derivative), aminoglutethimide (anti-steroid), cyclosporine A (immunosuppressant) and naringenin (flavonoid) on XO were elucidated using the chip-based assay in the presence or absence of a free radical scavenging enzyme (SOD, superoxide dismutase). Drug analogs were assessed for their ability to inhibit XO, which loads to a reduction in the conversion of nitroblue tetrazolium (NBT) to NBT diformazan. The reduction of NBT to NBT formazan in the presence of XO and drug analog can be seen. The PDA microchip system employed in this study consists of an array of red light-emitting diodes (LEDs) focused precisely onto the photodetectors of the PDA chip. The ability of drugs to inhibit XO was assessed based on NBT reduction. Free radicals produced due to the oxidation of xanthine by XO resulted in the reduction of NBT to insoluble NBT formazan. We report a new high-throughput chip-based xanthine assay to explore the XO inhibitory properties of drug analogs, along with their modes of action. The work presented here has important implications with regard to rapid and automated drug discovery screening processes in the pharmaceutical industry.