Voltammetric detection of vitamin D employing Au-MoS(2) hybrid as immunosensing platform

A voltammetric immunosensor based on molybdenum sulphide (MoS(2)) and gold nanoparticles (Au NPs) for the determination of 25-hydroxy vitamin D(3) (25(OH)D(3)) is reported. Anti-vit D (Ab-25(OH)D(3)) was immobilized onto the cysteamine-modified MoS(2) and Au NPs which were deposited onto a fluoride tin oxide (FTO) electrode (Ab/Cys/Au/MoS(2)/FTO). The MoS(2) sheets were prepared by hydrothermal method followed by an in situ growth of Au film onto the MoS(2)/FTO surface. Self-assembled monolayer (SAM) of cysteamine was synthesized onto the Au/MoS(2)/FTO which acts as a linker to covalently bind Ab-25(OH)D(3). The Ab-25(OH)D(3)-immobilized Cys/Au/MoS(2)/FTO was used to detect 25(OH)D(3) using differential pulse voltammetry. The electrochemical system provided an anodic peak current at a potential of +0.21 V vs. Ag/AgCl (satd. KCl) of ferricyanide/ferrocyanide redox couple. The detection principle relies on the inhibition of electron transfer at the electrode surface owing to the hindrance caused by the formation of immune complex between Ab-25(OH)D(3) and 25(OH)D(3). The immunosensor shows linear response from 1 pg mL(−1) to 100 ng mL(−1) 25(OH)D(3) and a sensitivity of 189 μA [log (pg mL(−1))](−1) cm(−2) along with a low limit of detection (LOD) of 0.38 pg mL(−1). The immunosensor is highly selective towards 25(OH)D(3) and presented a long shelf life of 28 days. Also, the immunosensor exhibits satisfactory performance towards spiked human serum samples with recovery between 95.1 and 102% (RSD 1.15–3.22%). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00604-021-04862-6.