Ferrocene tagged primary antibody generates electrochemical signal: An electrochemical immunosensing platform for the monitoring of vitamin D deficiency in clinical samples

In this paper, a new kind of ultrasensitive and low-cost electrochemical immunosensing probe was designed to monitor vitamin D deficiency using 25(OH)D3 as a clinical biomarker. Ferrocene carbaldehyde conjugated on Ab-25(OH)D3 antibodies was used as an electrochemical probe for generating signals. The graphene nanoribbon-modified electrode (GNRs) was used to immobilize the (Ab-25(OH)D3-Fc) conjugate. The high electron transferability, greater surface area, and effective biocompatibility of GNRs enabled the capture of the greater number of primary antibodies (Ab-25(OH)D3). The developed probe was structurally and morphologically characterized. The step-wise modification was investigated by electrochemical techniques. The direct electrochemistry of ferrocene enabled 25(OH)D3 biomarker detection with excellent sensitivity. The reduction in peak current was proportional to the concentrations of 25(OH)D3 in the range of 1–100 ng mL−1 with a 0.1 ng mL−1 limit of detection. The probe was tested in terms of reproducibility, repeatability, and stability. Finally, the developed immunosensing probe was applied in serum samples for 25(OH)D3 quantification, and no significant difference was noticed in the assay results when compared with the standard chemiluminescent immunoassay (CLIA) method. The developed detection strategy has a wider scope for future potential clinical diagnostics applications.