Ratiometric electrochemical immunosensor triggered by an advanced oxidation process for the ultrasensitive detection of carcinoembryonic antigen

Conventional electrochemical immunosensors often achieve detection purposes through a single signal output, but its electrical signal is susceptible to external environmental interference, which seriously interferes with the sensitivity and repeatability of the sensors. In this work, a novel ratiometric electrochemical immunosensor triggered by an advanced oxidation process (AOP) was developed for the ultrasensitive detection of carcinoembryonic antigen (CEA). The sensor uses gold nanoparticle-reduced graphene oxide/methylene blue adsorbed by sodium alginate (Au-rGO/MB-SA) as matrix to immobilize primary antibody (Ab 1 ) and Ag nanoparticles-functionalized egg yolk structure Co 3 O 4 @SiO 2 (Co 3 O 4 -Ag@SiO 2 ) as a marker to label secondary antibody (Ab 2 ). When the detection solution contains peroxymonosulfate (PMS), the signal probe Co 3 O 4 -Ag@SiO 2 activates PMS to produce SO 4 •− /•OH radicals to degrade MB, thus generating two independent electrochemical signals with opposite directional changes (I Ag and I MB ). The sensitivity of the sensor is improved due to an enhanced response magnitude on account of the processing of the dual selective responsive signals to yield a response magnitude greater than that of the signal from a single sensor. Square wave voltammetry (SWV) analysis shows that the dual signal ratio (I = I Ag /I MB ) has a linear relationship with the logarithm of the CEA concentration in the range of 0.01 pg/mL to 40 ng/mL, and the detection limit is as low as 3.42 fg/mL. In addition, the sensor has good selectivity and reproducibility, showing great promise for applications in bioanalysis and disease diagnosis. • The ratiometric electrochemical immunosensor triggered by AOP has better sensitivity. • The good activation ability of Co 3 O 4 -Ag@SiO 2 for PMS accelerates the degradation of MB. • Au-rGO improves the conductivity of the sensor and increases the load of the Ab 1 . • Lower LOD (3.42 fg/mL) and better repeatability compared to single signal sensors.