Disposable impedimetric nano-immunochips for the early and rapid diagnosis of Vitamin-D deficiency

Abstract

Deficiency of Vitamin D is often misdiagnosed as its symptoms may not be manifested for several years. Long-standing of this deficiency is associated with cancer, osteoporosis, diabetes, blood clotting disorders, and recently it was involved in the progression of coronavirus 2019 infection. Therefore, the development of a point-of-care test for Vitamin D is extremely necessary to achieve early, faster, and personal diagnosis. Serum 25-hydroxyvitamin-D3 (25(OH)D3) is clinically considered as one of the remarkable biomarkers for the direct determination of vitamin D level.Herein, nanostructured-immunosensors were designed for the label-free impedimetric determination of 25(OH)D biomarker in human serum. To fabricate the sensing probe, the targeting antibody (anti-25(OH)D3) was chemically conjugated on the nanocomposite surface (AuNPs/RGO-SeO2) using 4-aminothiophenol (4-ATP) and glutaraldehyde (GA) as cross-linking agents. Through the assay optimization, screening of nanomaterials, determining the best ratio of the nanocomposite, adjusting the time of SAM-formation, and identifying the degree of cross-reactivity with other non-targeting molecules were studied and optimized. Eventually, a linear dynamic range of 0.05–200 ng/mL, and the lower limit of detection of 0.01 ng/mL was achieved. Furthermore, the proposed immunosensor was tested for the detection of 25(OH)D3 in human serum samples, and the results were in a good agreement with the result obtained by the ELISA test. Providing high selectivity, reproducibility, and stability, this designed sensor is recommended for clinical diagnosis of Vitamin D.

Keywords

• Label-free impedimetric immunosensor
• 25-Hydroxy vitamin D3
• Vitamin D deficiency
• Nanocomposites
• Disposable sensor chips