Anal Chim Acta 2019 Dec 13;1086:103-109. Epub 2019 Aug 13.
School of Chemistry and Chemical Engineering, Institute of Surface Analysis and Chemical Biology, University of Jinan, Jinan, 250022, China; College of Optoelectronics Technology, Chengdu University of Information Technology, Chengdu, 610225, China. Electronic address:
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) and copper ions (Cu) to fabricate two spatial-resolved electrochemical signals with different response manners towards NMP22. SMNPs chelated with Pb were used for the immobilization of captured primary anti-NMP22. And SMNPs chelated Cu 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 decreases while the stripping peak current of Cu increases. Thus, ratiometric electrochemical signals could be provided for NMP22 detection. The immunosensor presented a linear concentration range from 0.013 U mL to 6.7 U mL with a limit of detection of 0.005 U mL towards NMP22. Meanwhile, satisfactory reproducibility, stability and selectivity of the immunosensor were demonstrated.