Novel 2D CuFe-MOF-based immunoprobe: Addressing antifouling electrochemical immunosensing inadequate sensitivity challenge

Rational design of antifouling interfaces in electrochemical immunosensor was an efficient approach to resist nonspecific adsorption in complex sample. Nonetheless, it remained a challenge, namely, most antifouling materials had poor electrical conductivity and their introduction resulted in high impedance at the sensing interface, greatly reducing the sensitivity of the detection. Herein, a novel immunoprobe was fabricated by utilizing 2D CuFe-MOF composed by Cu and Fe as metal nodes and 1,4-benzenedicarboxylic acid (H2BDC) as an organic ligand. Due to the planar conjugated structure of the ligand, electronic transition can be greatly promoted. This property of the ligand was applied to improve the conductivity of the antifouling sensing interface. Therefore, the sensitivity of the sensor was greatly enhanced. Because of the synergistic catalysis of Fe-Cu bimetallic sites, in presence of H2O2, abundant hydroxyl radicals were generated for further cascade amplification of electrochemical signals. The hyaluronic acid (HA) and 5-serotonin hydrochloride (ST) were cross-linked on electrode to form a hydrogel substrate to resist fouling from serum sample. Given the integration of the novel probe and the antifouling substrate, the method achieved remarkably low limit of detection (2.6 fg mL-1) for squamous cell carcinoma antigen (SCCA) in human serum samples over a wide linear range from 100 fg mL-1 to 100 ng mL-1. The method provided a pervasive route for designing sensitive antifouling interfaces.