A Sensitive Sandwich-Type Electrochemical Immunosensor for Carbohydrate Antigen 19-9 Based on Covalent Organic Frameworks

Since carbohydrate antigen 19-9 (CA 19-9) is a significant biomarker for the clinical diagnosis and treatment of pancreatic cancer, a sensitive sandwich-type immunosensor was proposed with an epoxy functionalized covalent organic framework (EP-COFTTA-DHTA) as the antibody carrier and an electroactive COFTTA-2,6-NA(OH)2 as the signal amplification probe for the sensitive detection of CA 19-9. The flexible covalent linkage between the epoxy-functionalized EP-COFTTA-DHTA and the antibodies was employed to improve the dynamics of the antigen–antibody interaction significantly. Meanwhile, AuNPs@COFTTA-2,6-NA(OH)2 with abundant electroactive sites enhanced the current response of the immunoreaction significantly. After optimizing the incubation time and concentration of the antibody, CA 19-9 was quantitatively detected by differential pulse voltammetry (DPV) based on the sensitive sandwich-type immunosensor with a low detection limit of 0.0003 U/mL and a wide linear range of 0.0009–100 U/mL. The electrochemical immunosensor exhibits high specificity, stability and repeatability, and it provides a feasible and efficient method for the pathologic analysis and treatment of tumor markers.