A sandwich-type electrochemical immunoassay for ultrasensitive detection of non-small cell lung cancer biomarker CYFRA21-1

Many studies confirm that the aberrant expression of Cytokeratin 19 fragment 21-1 (CYFRA21-1) is highly correlated with non-small cell lung cancer (NSCLC), especially for squamous cell carcinoma. Herein, we report a sandwich-type electrochemical immunosensor based on signal amplification strategy of multiple nanocomposites to test CYFRA21-1 selectively and sensitively. The proposed immunosensor fabricated by three-dimensional graphene (3D-G), chitosan (CS) and glutaraldehyde (GA) composite on the glass carbon electrode (GCE) with a large surface area is prepared to immobilize primary antibodies (Ab1) and provide excellent conductivity. To further amplify the electrochemical signal, the trace tag on the foundation of gold nanoparticles (AuNPs) is coated with amino-functionalized carbon nanotube (MWCNT-NH2) nanocomposite through thionine linking, which provides more amino groups to capture more horseradish peroxidase-labeled antibodies (HPR-Ab2) and enhances the conductivity. Under optimal conditions, the developed immunosensor exhibits excellent analytical performance for the determination of CYFRA21-1 with a wide linear range from 0.1 to 150 ng·mL− 1 and a low detection limit (LOD) of 43 pg·mL− 1. Furthermore, satisfactory results are obtained for the determination of CYFRA21-1 in real clinical serum samples, indicating the potential of the immunoassay to be applied in clinical analysis.