Novel Ratiometric Electrochemical Biosensor for Determination of Cytokeratin 19 Fragment Antigen 21-1 (Cyfra-21-1) as a Lung Cancer Biomarker

Previous studies confirm that aberrant expression of cytokeratin 19 fragment antigen 21-1 (cyfra-21-1) is highly correlated with non-small cell lung cancer (NSCLC). Herein, a proportional electrochemical immunosensor based upon a methylene blue/cadmium telluride/molybdic sulfide (MB/CdTe/MoS2) nanocomposite was successfully fabricated for detecting tumor marker cyfra-21-1. The result indicates that MB/CdTe/MoS2 modified on the surface of a glassy carbon electrode (GCE) supplies a large surface area for immobilizing primary antibodies (Ab1), ensuring high selectivity and sensitivity. To further amplify the sensitivity of the biosensor, ferrocenecarboxylic acid (Fc-COOH) linked with amino-functionalized secondary antibodies through amido bond (Ab2-Fc) as the “signal-on” probe and MB-modified with MoS2 with a large specific surface area as the “signal-off” probe increase the number of active sites for integration of Ab2-Fc/Ag/BSA/Ab1/MB/CdTe/MoS2/GCE electrode with the linker cyfra-21-1 (Ag). Meanwhile, CdTe accelerates the electron transfer and enhances the MB current, improving the sensitivity and detection limit. The presence of cyfra-21-1 led to both the decreasing response of MB and increasing current responses of Fc upon the electrode. Based upon this strategy, the determination of cyfra-21-1 was achieved in a linear range from 10 pg/mL to 10,000 ng/mL with the lowest detectable concentration of 10 pg/mL (signal-to-noise ratio of 3). The electrochemical immunosensor performs a sensitive determination of cyfra-21-1, possibly providing a practical strategy for the clinical analysis of lung cancer.