A sensitive sandwich-type electrochemical immunosensor using nitrogen-doped graphene/metal-organic framework-derived CuMnCoO_x and Au/MXene for the detection of breast cancer biomarker

In terms of cancer-related deaths among women, breast cancer (BC) is the most common. Clinically, human epidermal growth receptor 2 (HER2) is one of the most commonly used diagnostic biomarkers for facilitating BC cell proliferation and malignant growth. In this study, a disposable gold electrode (DGE) modified with gold nanoparticle-decorated Ti₃C₂T_x (Au/MXene) was utilized as a sensing platform to immobilize the capturing antibody (Ab₁/Au/MXene). Subsequently, nitrogen-doped graphene (NG) with a metal-organic framework (MOF)-derived copper-manganese-cobalt oxide, tagged as NG/CuMnCoO_x, was used as a probe to label the detection antibody (Ab₂). A sandwich-type immunosensor (NG/CuMnCoO_x/Ab₂/HER2-ECD /Ab₁/Au/MXene/DGE) was developed to quantify HER2-ECD. NG/CuMnCoO_x enhances the conductivity, electrocatalytic active sites, and surface area to immobilize Ab₂. In addition, Au/MXene facilitates electron transport and captures more Ab₁ on its surface. Under optimal conditions, the resultant immunosensor displayed an excellent linear range of 0.0001 to 50.0 ng. mL⁻¹. The detection limit was 0.757 pg·mL⁻¹ with excellent selectivity, appreciable reproducibility, and high stability. Moreover, the applicability for determining HER2-ECD in human serum samples indicates its ability to monitor tumor markers clinically.