Electrochemical ultrasensitive detection of CYFRA21-1 using Ti3C2Tx-MXene as enhancer and covalent organic frameworks as labels

The concentration level of cytokeratin fragment antigen 21-1 (CYFRA21-1) can be used as an important indicator for predicting non–small cell lung cancer (NSCLC). Here, a sandwich-type electrochemical immunosensor for ultrasensitive detection of CYFRA21-1 is developed. The sensor based on a combination of gold nanoparticle (AuNPs) decorated Ti3C2Tx-MXene (Au-Ti3C2Tx) as the substrate enhancer, and toluidine blue (TB) modified AuNPs doped covalent organic framework (COF) polymer as the signal tag (TB-Au-COF). The Au-Ti3C2Tx is used to capture numerous primary antibodies and accelerate the electron transfer rate of the substrate, while the TB-Au-COF can be applied to provide a large number of signal units TB and secondary antibodies. These features of composites endow the proposed immunosensor with high sensitivity and current response to CYFRA21-1. Under optimum conditions, the immunosensor offers a wide current response for CYFRA21-1 from 0.5–1.0 × 104 pg·mL−1 with a detection limit of 0.1 pg·mL−1. Furthermore, the biosensing platform can be applied for CYFRA21-1 detection to analyze real serum samples, providing an effective and useful avenue for the applicability of Au-Ti3C2Tx and TB-Au-COF composite materials in biosensing field.