Magneto-controlled electrochemical immunosensor for direct detection of squamous cell carcinoma antigen by using serum as supporting electrolyte

A new magneto-controlled microfluidic device for direct electrochemical determination of squamous cell carcinoma antigen (SCC-Ag) in serum was designed by using anti-SCC antibody (SCC-Ab)-functionalized magnetic mesoporous nanogold/thionine/NiCo2O4 hybrid nanostructures as immunosensing probes (P1-Ab) and horseradish peroxidase-SCC-Ab conjugates-labeled nanogold/graphene nanosheets as signal tags (P2-Ab). In the presence of the analyte SCC-Ag, the sandwich immunocomplex was formed between the immunosensing probes and the signal tags. With the aid of an external magnet, the formed immunocomplex was attached to the microfluidic device. The assay was implemented in newborn calf serum (NBCS) containing 2.5 mM H2O2 based on the labeled peroxidase on the P2-Ab toward the catalytic reduction of H2O2. Under optimal conditions, the increase in the current was proportional to the concentration of SCC-Ag from 2.5 pg/mL to 15 ng/mL. The detection limit (LOD) was 1.0 pg/mL SCC-Ag at 3sB. The electrochemical immunoassay displayed an acceptable precision, selectivity and stability. Clinical serum specimens were assayed with the method, and the results were in acceptable agreement with those obtained from the referenced electrochemiluminescent method. Importantly, the method can be suitable for on-line use in the mass production of miniaturized lab-on-a-chip devices and open a new opportunity for protein diagnostics and biosecurity.