Dual-Mode Electrochemical Assay of Prostate-Specific Antigen Based on Antifouling Peptides Functionalized with Electrochemical Probes and Internal References

Sensitive and selective detection of target analytes in complex biological samples is currently a major challenge. Herein we constructed a dual-mode antifouling electrochemical sensing platform for the detection of prostate-specific antigen (PSA) based on two kinds of antifouling peptides functionalized with a graphene oxide–Fe3O4–thionine (GO-Fe3O4-Thi) probe and internal reference ferrocene (Fc), respectively. The longer peptide (Pep1) modified with the GO-Fe3O4-Thi probe was designed to contain a peptide sequence (HSSKLQK) capable of being recognized and cut by PSA. The GO-Fe3O4-Thi probe functions not only as a peroxidase mimick (GO-Fe3O4) but also works as an electrochemical probe due to the presence of thionine (Thi). The concentration of PSA can be measured through both the increase of differential pulse voltammetry (DPV) signal change of Thi and the decrease of chronoamperometry (CA) signal of the reduction of H2O2 electrocatalyzed by GO-Fe3O4. The shorter peptide (Pep2) was tagged with Fc, whose DPV signal remained constant and was independent of the presence of PSA, and it was used as an internal reference to ensure the reliability and accuracy of the measurement. The dual-mode PSA sensor exhibits a wide linear range from 5 pg/mL to 10 ng/mL, with low detection limits of 0.76 and 0.42 pg/mL through DPV and CA modes, respectively. More importantly, owing to the antifouling capability of the designed peptides, the biosensor performances remained operable even in human serum, indicating feasibility of the electrochemical biosensor for practical PSA quantification in complex samples.