Electrochemical immunosensor based on chitosan-gold nanoparticle/carbon nanotube as a platform and lactate oxidase as a label for detection of CA125 oncomarker.

In this work, a novel simple and sensitive electrochemical immunosensor was developed based on lactate oxidase as a single electrochemical probe for the detection of carcinoma antigen 125 (CA125). Chitosan-gold nanoparticle/multiwall carbon nanotube/graphene oxide (CS-AuNP/MWCNT/GO) was used as the electrode substrate to increase the electrode specific surface area and improve the protein immobilization and the electrochemical performance of the electrode in terms of oxidation of H2O2. Due to the peroxidase-like function of CS-AuNP, the oxidation peak of H2O2 was observed at a very low potential (0.034 V). The lactate oxidase is used, for the first time, as the single-enzyme label in a sandwich type immunosensor. In the optimum condition, the designed immunosensor exhibited two linear ranges (0.01-0.5 U/mL and 0.5-100 U/mL) by chronoamperometry (CHA). The limit of detection (LOD) was estimated to be 0.002 U/mL. The immunosensor displayed excellent reproducibility and stability with remarkable selectivity in terms of the detection of CA125 even in the human serum samples as compared to the ELISA. In conclusion, the engineered immunosensor is proposed as an ultra-sensitive tool for the detection and monitoring of CA125 in the human serum.