Detection of serum uric acid using the optical polymeric enzyme biochip system

An optical polymeric biochip system based on the complementary metal oxide semiconductor (CMOS) photo array sensor and polymeric enzyme biochip for rapidly quantitating uric acid in a one-step procedure was developed. The CMOS sensor was designed with N⁺/P-well structure and manufactured using a standard 0.5 μm CMOS process. The polymeric enzyme biochip was immobilized with uricase-peroxidase and used to fill the reacting medium with the sample. This study encompasses the cloning of the Bacillus subtilis uricase gene and expression in Escherichia coli, as well as the purification of uricase and measurement of its activity. The cloned uricase gene included an open reading frame of 1491 nucleotides that encodes a protein of approximately 55 kDa. The expression of the putative MBP-fusion protein involved approximately 98 kDa of the protein. The CMOS sensor response was stronger at a higher temperature range of 20-40°C, with optimal pH at 8.5. The calibration curve of purified uric acid was linear in the concentration range from 2.5 to 12.5 mg/dL. The results obtained for serum uric acid correlated quite closely with those obtained using the Beckman Synchron method.