A sandwich electrochemical immunosensor based on MXene@dual MOFs for detection of tumor marker CA125

The detection signal of carbohydrate antigen 125 (CA125) can be quantitatively amplified via the dual metal-organic framework (MOF) sandwich strategy. We propose a versatile method for synthesizing uniform MXene and MIL-101(Fe)-NH₂ composites that combine the advantages of both materials to build a base layer with superb performance. MXene exhibits excellent electrical conductivity and high surface area. The mesoporous MIL-101(Fe)-NH₂ not only increases the loading capacity of the primary antibody but also possesses the catalytic activity of the metal center (Fe). UiO66 loaded with methylene blue (MB) was fabricated as an electrochemical immunosensor signal tag to enable the detection of CA125. The mixture of MXene and MIL-101(Fe)-NH₂ prepared as the substrate was fixed by chitosan rich in amino groups. As the signal amplification sector, UiO66@MB enhanced secondary antibody loading capacity and generated a redox signal enabling the detection of antigenic substances. The proposed electrochemical immunosensor demonstrated high sensitivity with a low limit of detection (LOD) of 0.006 U/mL. Therefore, the dual MOF sandwich-based immunosensor provides a novel method for the early diagnosis of CA125.