Protein nano Dots conjugated AuNP, poly-Lysine biointerface for the selective voltammetric estimation of Melatonin in pharmaceutical and food samples

Attributed to the compromised charge transfer of Protein-derived nanomaterials, their beneficial traits as an extraordinarily selective and specific biorecognition element for the electrochemical sensors haven't been fully exploited. Here in this work, we report a facile approach to electrochemically fabricate a Protein Nanodots (PNDs) conjugated AuNP, poly-Lysine biointerface for the voltammetric estimation of Melatonin. Using bovine serum albumin, PNDs decorated with active functional groups were derived and further tailored with AuNP-poly Lysine to achieve the facilitated charge-transfer and specific interactions with Melatonin. After detailed topographical and chemical characterization of the fabricated surface, its ability to estimate Melatonin was probed in a linear concentration range of 0.1–200 µM. The fabricated biointerface manifested a ∼3-fold magnification in Mel peak current with a potential shift of ∼60 mV compared to the unmodified electrode. The potential shift was attributed to the synergistic effect of PNDs and Au-poly-Lysine layer leading to the electro-catalytic behavior and facilitated charge-transfer due to specific interactions between Melatonin/AuNP-PLL/PND. Consequently, sensor demonstrated a LOD of 31.6 nM without any substantial interference of Uric acid, Ascorbic acid, and Hypoxanthine. The estimation of Melatonin in commercial pharmaceutical formulation as well as food sample (Mung Beans) was carried out to investigate the practical application.