A novel ratiometric electrochemical immunosensor for the detection of cancer antigen 125 based on three-dimensional carbon nanomaterial and MOFs

Accurate and sensitive detection of cancer antigen 125 (CA125) is important in early ovarian cancer diagnosis and monitoring. In the present work, a novel electrochemical ratiometric immunosensor for the determination of CA125 based on three-dimensional reduced graphene oxide/multi-walled carbon nanotube carboxylic acid- thionine (3DrGO/MWCNTs-Thi) and UIO-66-NH 2 /ferrocenecarboxylic acid (UiO-66-Fc) was constructed. 3DrGO/MWCNTs-Thi of immobilized primary antibody (Ab 1 ) and UiO-66-Fc of labeled second antibody (Ab 2 ) were used as capture probes and signaling probes for CA125, respectively. As the concentration of CA125 increases, the oxidation peak currents (I Thi and I Fc ) generated by the two materials were changed in opposite directions, and therefore the ratio of the currents (I Thi /I Fc ) was negatively correlated with the concentration of CA125. Thanks to the amplification of high loading of signaling molecules by the framework nanocomposites and the ratiometric strategy, the constructed electrochemical immunosensor exhibits outstanding accuracy, stability, and sensitivity. Under optimal conditions, the detection range spanned from 0.01 U mL −1 to 80 U mL −1 , with a calculated limit of detection (LOD) of 0.0089 U mL −1 . The immunosensor was successfully applied to real serum sample tests, indicating its potential for clinical detection applications.