Antibody-functionalized MXene-based electrochemical biosensor for point-of-care detection of vitamin D deficiency

Clinical studies routinely show that individuals suffer from vitamin D deficiency, which can result in health complications that include cardiovascular disease, autoimmune disorders, neurodegenerative diseases, and different skeletal deformities. Given its integral role in homeostasis and connection to many pathologies, early diagnosis of vitamin D deficiency is crucial. However, monitoring vitamin D levels is challenging, particularly in remote regions, due to the cost, time, and complexity of existing methods. Here, we develop an electrochemical biosensor for vitamin D based on antibody-functionalized MXenes, offering clinically relevant sensitivity, specificity, and amenability for point-of-care testing. Ti₃C₂T_x MXene nanosheets are amine-functionalized by electrostatically-driven modification with polyethylenimine, whose functionalities are then used for covalent conjugation of anti-vitamin D antibodies via glutaraldehyde chemistry. This platform achieves a detection limit of 1 pg mL⁻¹ with a dynamic range (0.1–500 ng mL⁻¹) that covers clinically relevant deficiency, insufficiency, sufficiency, and toxicity.