Amine Functionalized Noble Metal: Metal Oxide Nanohybrid for Efficient Electrochemical Determination of 25-Hydroxy Vitamin-D 3 in Human Serum

Quantification of 25-hydroxy vitamin-D 3 (25-OHVD 3 ) is important because its deficiency is related to numerous diseases, including osteoporosis, depression, diabetes, heart disease, certain autoimmune conditions, and even Covid-19. In the present study, noble metal-metal oxide nanohybrid based on L-cysteine functionalized gold decorated zirconia nanoparticles (Cys-Au@ZrO 2 NPs) were synthesized with the objective of enhanced electrochemical behavior, stability, availability of functional group to covalently bind with biomolecules, and developing an efficient immunosensor for 25-OHVD 3 detection. The formation of Au@ZrO 2 NPs and further Cys functionalization was validated by various characterizations. Cys-Au@ZrO 2 NPs were electrodeposited onto ITO substrate and further modified with antibodies specific to 25-OHVD 3 (ab-25VD 3 ) and bovine serum albumin (BSA) to build an immunosensing platform for 25-OHVD 3 detection. The fabricated BSA/ab-25VD 3 /Cys-Au@ZrO 2 /ITO immunosensor demonstrated an improved sensitivity of 2.01 μ A ng −1 ml cm −2 , LOD of 3.54 ng ml −1 for the linear detection range of 1–50 ng ml −1 with regression constant of 0.98. Moreover, the analytical performance of the BSA/ab-25VD 3 /Cys-Au@ZrO 2 /ITO immunosensor in determining 25-OHVD 3 in human serum samples collected from four healthy people yielded satisfactory results that were highly correlated with the conventional enzyme-linked immunosorbent assay (ELISA).