GQD-Decorated Dual Electrochemical Biosensor for the Simultaneous Detection of Ferritin and Vitamin D3 in Serum Samples

Ferritin facilitates the transportation of iron molecules, plays crucial roles in metabolic, circulatory, and immune-regulatory functions, serving as a pivotal biomarker for assessing the risk of anaemia due to iron deficiency. In this study, graphene quantum dots (GQDs), zero-dimensional nanomaterials renowned for their exceptional optical and electrical properties, were employed as a matrix for the development of an electrochemical sensor. The synthesized GQDs were analysed via FT-IR, UV‒Vis spectroscopy, XRD, FE-SEM, HR-TEM and EDX. Additionally, surface modifications were investigated via electrochemical impedance spectroscopy (EIS), FE-SEM and FT-IR spectroscopy. Specificity and interference studies were also conducted using Vitamin B 12 , Folic acid (VB 9 ), Vitamin C, Interleukin-6, Interleukin- β . The biosensor exhibited excellent repeatability, with a % RSD of 4.04%, and the reproducibility of the sensor yielded a % RSD of 0.52%. Electrochemical analyses, including cyclic voltammetry (CV) and differential pulse voltammetry (DPV), revealed a sensitivity of 7381.2 μA mm −2 ng −1 , with a limit of detection (LOD) of 2.0 fg ml −1 Furthermore, simultaneous detection of vitamin D 3 and ferritin was achieved via a single electrode equipped with two working areas. Through the CV technique, the sensor chip demonstrated successful concurrent detection of both analytes. Stability of the sensor was checked for 6 months with an overall decrease of 9.7% current and in-house synthesis of SPPE was also done. Once developed, the sensor was validated with patient serum samples of known concentrations and revealed that the current‒concentration relationship was analogous in both clinical and standard samples, suggesting potential clinical applications.