Electrochemical Immuno-Biosensor for the Rapid Determination of Nuclear Matrix Protein 22 (NMP22) antigen in Urine Samples by Co(III) Phthlocyanine/Fe3O4/Au Collide Coimmobilized Electrode

A novel immunosensor is proposed for the rapid separation-free determination of nuclear matrix protein 22 (NMP22) antigen in human urine. The immunosensor is prepared by co-immobilizing HRP-NMP22 antibody, Co(III) phthalocyanine (CoPc), on a Fe3O4/Au colloid -modified gold electrode (HRP-Ab-NMP22/Fe3O4/Au/CoPc CME) using the self-assembly technique in which CoPc was as the electron transfer medium. The modified electrode shows an excellent electrocatalytic activity for NMP22 antigen in phosphate buffer solution (pH 7.0). After the immunosensor is incubated with NMP22 antigen solution at 37 °C for 20 min, the access of activity center of the HRP to electrode is partly inhibited, which leads to a linear decrease in the catalytic efficiency of HRP in the reduction of immobilized CoPc by H2O2 at –50 mV at NMP22 antigen concentration of 1.2–200 ng ml–1. The detection limit was 0.5 ng ml–1. The immunosensor was successfully utilized for the determination of NMP22 antigen from the urine samples of bladder cancer patients, which shows good repeatability, stability, and anti-interference. This method decreases the detection cost and shortens the analytical time, thus would be valuable in clinical immunoassay for the identification of bladder cancer.