Dual-Mode Electrochemical Competitive Immunosensor Based on Cd 2+ /Au/Polydopamine/Ti 3 C 2 Composite and Copper-Based Metal-Organic Framework for 17β-Estradiol Detection.

Herein, a dual-mode electrochemical competitive immunosensor was constructed for the detection of 17β-estradiol (E2) based on differential pulse voltammetry (DPV) and chronoamperometry ( i - t ). During the immune recognition process, the E2 antibody (E2-Ab) was immobilized on the Cd 2+ /Au/polydopamine/Ti 3 C 2 (Cd 2+ /Au/pDA/Ti 3 C 2 ) composite-modified electrode; then, the E2-conjugated bovine serum albumin (E2-BSA) was labeled with a copper-based metal-organic framework (Cu-MOF) and competed with E2 in combining the E2-Ab. The Cu-MOF was not only an electroactive species but also possessed good electrocatalytic activity toward H 2 O 2 . Thus, E2 could be quantified according to the peak current change of the Cu-MOF in DPV curve or the variation of H 2 O 2 reduction current. For DPV quantification, Cd 2+ was introduced as an internal reference in this case, and a highly reproducible ratio readout was obtained. The as-prepared dual-mode E2 electrochemical immunosensor showed good linear relationship in the ranges of 1 pg mL -1 -10 ng mL -1 (DPV) and 10 pg mL -1 -10 ng mL -1 ( i - t ), and the detection limits were 0.47 and 5.4 pg mL -1 (S/N = 3), respectively. Furthermore, the dual-mode electrochemical immunosensor exhibited good practicability in real sample analysis.