Ti3C2 MXene nanosheet-based capacitance immunoassay with tyramine-enzyme repeats to detect prostate-specific antigen on interdigitated micro-comb electrode

Abstract An interdigitated capacitance immunosensing system based enzymatic biocatalytic precipitation on micro-comb electrode was designed for the sensitive detection of prostate-specific antigen (PSA) by coupling Ti 3 C 2 MXenes with tyramine signal amplification strategy. The immunosensor was prepared by immobilizing anti-PSA capture antibody on MXenes-coated interdigitated electrode, whereas gold nanoparticles heavily functionalized with horseradish peroxidase (HRP) and detection antibody were utilized as the signal-transducer tags. Introduction of interdigitated electrode was expected to enhance the sensitivity of capacitance immunosensor. This system mainly consisted of the sandwich-type immunoreaction, formation of tyramine-HRP repeats on gold nanoparticle and enzymatic biocatalytic precipitation. The concatenated HRP through the tyramine oxidized numerous 4-chloro-1-naphthol molecules into insoluble benzo-4-chlorohexadienone with the help of H 2 O 2 , and coated the modified immunosensor to keep free ions away from the electrode, thus causing the local alteration in the capacitance. Under optimum conditions, the change of the immunosensor in the capacitance increased with the increasing target PSA concentrations from 0.1 ng mL -1 to 50 ng mL -1 at a detection limit of 0.031 ng mL -1 . Moreover, the interdigitated capacitance immunosensor showed good reproducibility, high specificity and acceptable accuracy for the analysis of human serum specimens in comparison with those obtained from commercial human PSA ELISA kit. Importantly, Ti 3 C 2 MXenes-based interdigitated capacitance transducer open new opportunities for protein diagnostics and biosecurity.