Erythrocyte-like BiVO₄ and bifunctional-nanozyme based dual-signal output electrochemical immunosensor: Enabling the...

Carbohydrate antigen 19-9 (CA19-9) serves as a valuable biomarker for pancreatic cancer (PC), offering the possibility for the early screening and diagnosis. Herein we developed a dual-signal output electrochemical immunosensor fabricated by PPy-BiVO₄ and Cu₂S-PtPd for the quantitative detection of CA19-9. Erythrocyte-like BiVO₄ was prepared by one pot hydrothermal method and functionalized by APTES. By utilizing BiVO₄ with specific surface area as substrate, massive polypyrrole nanotubes (PPy NTs) can be anchored on the sensor thus amplifying the signal effectively. Snowflake-like Cu₂S and spherical PtPd nanoparticles were synthesized by hydrothermal method. In addition, PtPd nanoparticles functionalized Cu₂S nanozyme (Cu₂S-PtPd nanozyme) is exploited as the catalytic active material and utilized to achieve the enrichment of target molecules in this study. Experimental results demonstrated that the immunosensor realized high sensitivity with the detection range of differential pulse voltammetry (DPV) is 0.001-100 U/mL and that of chronoamperometry (i-t) is 0.001-150 U/mL. The detection limit is 0.00017 U/mL for DPV and 0.00011 U/mL for i-t, along with superior selectivity, reproducibility and storage stability. At the same time, the immunosensor exhibits a high recovery rate for the analysis of human serum samples. The results indicate that the fabricated immunosensor will be promising in the early diagnosis and prognosis monitoring of cancer biomarkers.