Biochemical assay for serum creatinine detection through a 1-methylhydantoin and cobalt complex

Creatinine is a reliable indicator of renal function and degradation of muscular metabolism. Current analytical techniques for its measurement are limited by their cost and requirement of sophisticated instruments. In this work, we report a highly sensitive amperometric biosensor for creatinine by utilizing the one-step selective conversion of creatinine by creatinine deiminase. The novelty of the proposed sensor relies on the measurement of N-methylhydantoin produced in the reaction. The sensing chemistry comprises of creatinine deiminase as the receptor for creatinine, cobalt chloride as the electrochemically active recognition element, and methylene blue as the redox mediator. The sensing chemistry is immobilized on the glassy carbon electrode surface by physisorption. We have been able to provide a standalone device that reliably quantifies creatinine in serum and even whole blood, without any sample pre-processing. It is possible to measure creatinine in the clinically relevant range from 0.8 to 4 mg dL^-1 with this approach.