A label-free impedimetric immunosensor based on nitrogen-doped graphene acid for sensitive detection of vitamin D3

Abstract

Vitamin D deficiency is a major global health concern, affecting over one billion people worldwide, particularly those with limited sun exposure. Current detection methods provide reliable results but suffer from limitations, including high costs, complex sample preparation, and the need for specialized equipment. In this study, we present a simple metal-free electrochemical immunosensor based on nitrogen-doped graphene acid (NGA) for the detection of 25-hydroxy vitamin D3 (25-OH D3). The use of NGA, with its well-defined chemical composition, high density of carboxyl functional groups, and excellent biocompatibility, provided a stable and efficient platform for biomolecule immobilization without the need for complex surface modifications. The proposed immunosensor demonstrated high sensitivity (1.97 k ng1 mL cm2) and a working range of 3.96 to 48.83 ng mL1, aligning with clinically relevant vitamin D levels. Moreover, the developed immunosensor exhibited excellent specificity, with minimal cross-reactivity and strong resistance to non-specific adsorption. Furthermore, it maintained stable electrochemical performance for up to 30 days, demonstrating its suitability for practical applications. Compared to existing vitamin D sensors, our platform introduces a streamlined fabrication process that avoids heavy metals, improves reproducibility, and enhances accessibility for point-of-care diagnostics