Electrochemical immuno-biosensor for nuclear matrix protein 22 in urine samples by Co(III) phthlocyanine/Fe3O4/Au collide coimmobilized electrode

A novel immunosensor was proposed for the rapid determination without separation of nuclear matrix protein 22 (NMP22) antigen in human urine. The immunosensor was prepared by co-immobilizing hoseradish peroxidase (HRP) -NMP22 antibody, Co(III) phthalocyanine (CoPc) on a Fe3O4/Au collide -modified gold electrode (HRP-Ab-NMP22/ Fe3O4/Au colloid/CoPc CME) using the self-assembly technique in which CoPc was as electron immediate. 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 degrees C for 20 min, the access of activity center of the HRP to electrode is partly inhibited, which leads to a linear decrease of the catalytic efficiency of the HRP to the reduction of immobilized CoPc by H2O2 at - 50 mV in NMP22 antigen concentration ranges from 1.2 to 200 mu g/L. The detection limit was 0.5 mu g/L. The immunosensor was successfully utilized for the determination of NMP22 antigen in urine samples of bladder patients, which shows a good accuracy, precision and reproducibility. This method decreases the detection cost and shortens the analytical time, thus would be valuable for clinical immunoassay for bladder cancer.