Convenient and highly sensitive electrochemical biosensor for monitoring acid phosphatase activity

Abstract Acid phosphatase (ACP) is a potential biomarker for different diseases. Using the DNA extension-based biological signal amplification and redox recycling of electrochemical species on reduced graphene oxide (rGO)-modified electrode, we established here a highly sensitive, label-free and electrode immobilization-free electrochemical assay for ACP in diluted human serum samples. Target analyte of ACP catalyzes the de-phosphorylation of the 3′-PO4 termini of a ssDNA into 3′−OH on the magnetic beads, which subsequently initiates strand extension into long guanine-rich ssDNAs by the terminal deoxynucleotidyl transferase with pre-defined ratio of dGTP to dATP. The magnetic accumulation of the beads on the rGO-modified electrode thus yield largely enhanced current signals, due to redox recycling oxidation of the many guanine bases in the extended DNAs mediated by [Ru(bpy)3]2+. Such significant current amplification can therefore lead to sensitive electrochemical detection of ACP in the range from 5 to 100 U/L with a low detection limit of 0.52 U/L. High selectivity of the sensing method can also be obtained and the monitoring of ACP in diluted serum samples is demonstrated. With the significant advantages of simplicity and sensitivity, this assay approach holds great potential for convenient detection of other biomolecules such as alkaline phosphatase at low levels.