25-Hydroxy vitamin D3 electrochemical biosensor mediated by a truncated aptamer and CuCo2O4/N-CNTs

Abstract

The measurement of serum 25-hydroxyvitamin D3 (25(OH)D3) levels at the clinic is essential because of its significant role in immune function and bone metabolism as well as the relationship between its deficiency and diseases such as neurodegenerative, depression, cancer, diabetes, and cardiovascular diseases. This study describes a novel electrochemical aptasensor based on a rationally truncated aptamer for sensitive, selective and low-cost quantification of 25(OH)D3. The aptasensor contains a glassy carbon electrode modified with CuCo2O4/N-CNTs nanocomposite and an engineered aptamer. Three newaptamers(VDBA14-23, VDBA14-27, and VDBA14-35) were designed via truncation of the previously selected DNA aptamer (VDBA14, 56-mer). The sensitivity and selectivity of VDBA14 and new truncated aptamers toward 25(OH)D3 were studied through the differential pulse voltammetry technique. Introducing 25(OH)D3 changes the flexibility and conformation of the aptemers and the detection strategy is done based on the peak current intensity of the redox marker [Fe(CN)6]3−/4−. In the DPV tests, the sensors built with the probable G-quadruplex VDBA14-35 aptamer showed improved sensitivity and specificity toward 25(OH)D3 than the parent VDBA14. Under optimized experimental conditions, the aptasensor response decreases with increasing the concentration of 25(OH)D3 and is linear with the logarithm of 25(OH)D3 concentration in the range from 1 × 10−13 to 1 × 10−6 M. The detection limit of the VDBA14-35/CuCo2O4/N-CNTs/GCE sensing is 0.063 pM (based on 3Sb/m). The fabricated aptasensor is simple, low-cost, selective, and sensitive. This sensor would be of great benefit for the clinical diagnosis of 25(OH)D3.