Ultrasensitive detection of adrenocorticotropin hormone (ACTH) using disposable phenylboronic-modified electrochemical immunosensors

This work reports for the first time an electrochemical immunosensor for the determination of adrenocorticotropin hormone (ACTH). The immunoelectrode design involves the use of amino phenylboronic acid for the oriented immobilization of anti-ACTH antibodies onto screen-printed carbon modified electrode surfaces. A competitive immunoassay between the antigen and the biotinylated hormone for the binding sites of the immobilized antibody was performed. The electroanalytical response was generated by using alkaline phosphatase-labelled streptavidin and 1-naphtyl phosphate as the enzyme substrate. The electrochemical oxidation of the enzyme reaction product, 1-naphtol, measured by differential pulse voltammetry was employed to monitor the affinity reaction. Under the optimized working conditions, an extremely low detection limit of 18 pg/L was obtained. Cross-reactivity was evaluated against other hormones (cortisol, estradiol, testosterone, progesterone, hGH and prolactin) and the obtained results demonstrated an excellent selectivity. The developed immunosensor was applied to a human serum sample containing a certified amount of ACTH with good results.

► The development of an electrochemical immunosensor for ACTH is reported for the first time.
► The immunosensing approach involves the oriented immobilization of anti-ACTH onto phenylboronic acid-modified screen-printed carbon electrodes.
► The developed design exhibits an excellent analytical performance in terms of sensitivity, limit of detection (18 pg/L), selectivity, wide range of quantifiable antigen concentrations (0.025–1.0 pg/mL), and inter-assay reproducibility.
► This immunosensor can be envisaged as a useful and affordable analytical tool for the rapid determination of ACTH in clinical applications, as it has been outlined with the results obtained for the analysis of certified human serum samples.