Electrochemical impedance analysis of the CYFRA 21-1 antigen based on doxorubicin-initiated ROP signal amplification

Abstract

The cytokeratin-19-fragment antigen (CYFRA 21-1), a soluble cell fragment, which is liberated into the blood during the metaphase of apoptosis, is one of the characteristic biomarkers of non-small cell lung cancer (NSCLC). In this paper, the copolymer poly(ε-caprolactone)-b-poly(ethylene oxide) (Dox–PCL–PEO) produced by ring-opening polymerization (ROP) is applied to a label-free electrochemical immunoassay for CYFRA 21-1. First, under the catalysis of tetrabutylammonium fluoride (TBAF), 4-(2-trimethylsilylethynyl) benzoic acid (TEB) was removed from the trimethylsilyl group and fixed on the surface of the electrode through Au–C. Then, the initial antibody (Ab1) was attached to the TEB to specifically recognize CYFRA 21-1. After that, the copolymer Dox–PCL–PEO was connected to the secondary antibody (Ab2) as a signal amplifying unit. Finally, Ab2–Dox–PCL–PEO specifically recognized CYFRA 21-1 to form an antibody–antigen–antibody sandwich structure. Therefore, we finally developed a complete electrochemical impedance immunoassay for the detection of CYFRA 21-1. Under the optimum experimental conditions, the detection method had a high sensitivity, and a wide linear range (100 fg mL⁻¹–500 ng mL⁻¹) with a lower limit of detection (LOD) of 0.021 pg mL⁻¹, which is approximately 5.83 × 10⁻¹⁶ M What's more, it also showed high sensitivity, good selectivity and anti-interference in actual samples. Thus, there will be a good chance of early diagnosis of other tumor markers and biomolecules.