A new ratiometric electrochemical immunoassay for reliable detection of nuclear matrix protein 22

Ratiometric signal transducing strategies can improve the precision of immunoassay , which possess the unique merits of spatial-resolved signal readout and self-correcting towards possible false positive results. In this work, a new ratiometric electrochemical immunosensor has been developed for reliable detection of Nuclear matrix protein 22 (NMP22). Bioinspired synthetic melanin nanospheres (SMNPs) were elaborately chosen for the following considerations: 1) SMNPs can supply good biocompatible biorecognition interface for antibody anchoring; 2) SMNPs can chelate a large amount of lead ions (Pb 2+ ) and copper ions (Cu 2+ ) to fabricate two spatial-resolved electrochemical signals with different response manners towards NMP22. SMNPs chelated with Pb 2+ were used for the immobilization of captured primary anti -NMP22. And SMNPs chelated Cu 2+ were employed to prepare signal labels after anchored with anti -NMP22 antibody. After sandwich-type immunoreaction, with the increasing concentration of NMP22, the stripping peak current of Pb 2+ decreases while the stripping peak current of Cu 2+ increases. Thus, ratiometric electrochemical signals could be provided for NMP22 detection. The immunosensor presented a linear concentration range from 0.013 U mL −1 to 6.7 U mL −1 with a limit of detection of 0.005 U mL −1 towards NMP22. Meanwhile, satisfactory reproducibility, stability and selectivity of the immunosensor were demonstrated.