Dual-Labeled Octahedral Gold and Magnetic Microsphere Electrochemical Immunosensor for Ultrasensitive Determination of Carbohydrate Antigen-199 (CA199) by Differential Pulse Voltammetry (DPV)

To precisely detect CA199 antigen, a novel electrochemical immunosensor based on horseradish peroxidase (HRP) and glucose oxidase (GOD) double enzyme system was prepared. Thiol was adsorbed on the surface of nano-octahedral gold through Au-S self-assembly; the second antibody was labeled by glutaraldehyde ligase as a signal amplification reagent. Amino magnetic microspheres were used to connect GOD and bovine serum albumin (BSA) through glutaraldehyde. The biosensor displayed low detection limits of 0.2 U/mL and wide linear range (0.5–200 U/mL). This novel immunosensor improves the sensitivity of current detection, showing promising application prospects in the clinical immunoassay detection of CA199.