An electrochemical immunosensor for carbohydrate antigen CA125 based on electroactive COFs as a signal probe

Levels of CA125 are strongly associated with cervical, pancreatic, bowel and breast cancer. However, the common CA125 detection method has the disadvantages of poor repeatability, high cost, easy to be disturbed and poor stability. In this work, a COF based electrochemical immunosensor was developed for the rapid, sensitive and stable detection of CA125. The COF_Dha-Tab synthesized by 2,5-dihydroxyp-phenyldiformaldehyde (Dha) and 1,3,5-tris(4-aminophenyl)benzene (Tab) can better absorb primary antibody (Ab₁) of CA125 after epoxidation, and the COF_DAAQ-TFP synthesized by 2,6-diaminoanthraquinone (DAAQ) and 2,4,6-triformylphloroglucinol (TFP) was modified with AuNPs, which can not only improve the electrochemical performance but also provide a platform for loading secondary antibody (Ab₂). CA125 can be specifically recognized and captured by EP-COF_Dha-Tab adsorbed to Ab₁, which can further bind the signal probe AuNPs@COF_DAAQ-TFP/Ab₂. The signal response of the electroactive molecule COF_DAAQ-TFP is positively correlated with the concentration of CA125 to achieve the quantitative detection of CA125.The sensor exhibited a low detection limit of 0.0067 U/mL and a linear range from 0.01 to 100 U/mL. This work presents a novel approach utilizing electroactive COFs as signal probes for the sensitive and quantitative detection of carbohydrate antigens.