Gold‑platinum bimetallic nanoparticles coated 3-(aminopropyl)triethoxysilane (APTES) based electrochemical immunosensor for vitamin D estimation

We have developed a gold-platinum nanoparticles (Au-Pt NPs) supported on 3-(aminopropyl)triethoxysilane (APTES) modified fluorine tin oxide (FTO) glass electrode as a biosensing platform for the detection of 25-hydroxy vitamin D3 (25(OH)D3). The Au-Pt NPs were electro-deposited onto the APTES modified FTO electrode using chronoamperometry at a constant potential of -0.2 V for 350 s. The antibody against vitamin D3 (Ab-25(OH)D3) was immobilized covalently via glutaraldehyde cross linking chemistry. The successful immobilization of the matrix was confirmed through characterization techniques like FE-SEM, FT-IR, XRD, XPS, contact angle measurement, electrochemical characterizations such as cyclic voltammetry (CV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS). The DPV technique was employed for the detection of 25(OH)D3 using ferricyanide/ferrocyanide solution [Fe(CN)6]3-/4- as a redox mediator. The immunosensor presented a detection limit of 0.49 pg/mL with a quick response time of 12 min and an acceptable stability of 10 days, if stored at 4 °C. The proposed immunosenor is highly selective and sensitive for 25(OH)D3 and could be employed for the real-time quantification of vitamin D.