Rapid point-of-care detection of vitamin D deficiency using disposable electrochemical immunosensors based on a La2O3-WO3@CNT Bi-metal oxide nanocomposite.

Vitamin D deficiency represents a significant global health challenge closely associated with numerous chronic diseases, highlighting the need for early, reliable, and accessible detection methods. In this study, a disposable impedimetric immunosensor was developed based on a hybrid nanocomposite comprising lanthanum oxide (La2O3) and tungsten trioxide (WO3) integrated with carbon nanotubes (CNTs). The anti-vitamin D antibody was chemically immobilized onto La2O3-WO3@CNT-modified disposable printed electrodes via a self-assembled monolayer of 4-aminothiophenol, providing an efficient and stable bio-functional interface for antigen recognition. Consequently, comprehensive optimization was performed, including nanomaterial selection, self-assembled monolayer formation time, and assessment of cross-reactivity with non-target biomolecules. The resulting immunosensor exhibited superior electrochemical performance, demonstrating a wide linear detection range from 300 pg mL-1 to 180 ng mL-1. The incorporation of the La2O3-WO3@CNTs nanocomposite significantly enhanced the signal transduction efficiency, enabling sensitive and rapid determination of vitamin D levels in serum samples. This work presents a novel, label-free, and portable electrochemical immune-sensing platform utilizing printed disposable electrodes. By coupling advanced nanomaterial engineering with point-of-care technology, the proposed biosensor offers a robust, cost-effective, and user-friendly diagnostic tool for early detection and effective clinical monitoring of vitamin D deficiency.