An AuNPs-based electrochemical aptasensor for the detection of 25-hydroxy vitamin D₃

Vitamin D₃ (VD₃) is the main form of vitamin D and an essential nutrient for maintaining human life. Currently, traditional methods for detecting 25-hydroxyvitamin D3(25(OH)D₃) are complex and expensive. In this study, we constructed an accurate, sensitive, simple, and cost-effective label-free biosensor based on an aptamer for the detection of 25(OH)D₃. The aptamer-modified sulfhydryl adopted self-assembly as a way to stably immobilize at the glassy carbon electrode (GCE) surface modified by gold nanoparticles (AuNPs). Upon 25(OH)D₃ binding to the aptamer, the complexes inhibit electron transfer at the electrode surface, leading to reduced [Fe(CN)₆]^3-/4- redox peak current. Consequently, the quantity of 25(OH)D₃ that interacts with the electrode-bound aptamer correlates with the observed electric current response values. The Aptamer/AuNPs/GCE aptasensor achieved direct and highly sensitive detection of 25(OH)D₃ over a wide concentration range (1.0-1000 nM), with a limit of detection of 1.0 nM. At the same time, other molecules with a similar structure, such as 25(OH)D₂, Vitamin D₃, and Vitamin D₂, had lower response interference than 25(OH)D₃. Therefore, this biosensor has great potential to become a portable diagnostic device for 25(OH)D₃.