FUNCTIONALIZING GOLD NANOPARTICLES WITH A DNA APTAMER FOR BIOSENSING 25-HYDROXYVITAMIN D3

Abstract

Vitamin D influences over 400 processes in the human body and its deficiency is associated with several diseases such as uterine fibroids. Accessible point-of-need tools are required to detect 25-hydroxyvitamin D3 (25(OH)D3), a Vitamin D biomarker. This thesis investigated conjugation methods for the specific, yet structurally complex 25(OH)D3 aptamer, VDBA14, to gold nanoparticles (AuNPs), common biosensor transducers. Initial approaches using salt-aging, low pH, and freeze conjugation, evaluated with UV-Vis, fluorescence, and salt stability assays, were ineffective due to poor aptamer conjugation and the resulting AuNP aggregation. A promising development was the inclusion of an 18atom hexa-ethyleneglycol spacer between the aptamer and disulphide linker. Freeze conjugation of the modified aptamer improved AuNP stability, with conjugation confirmed by UV-Vis redshift and DNA FT-IR bands. Future experiments are required to demonstrate conjugation without destabilizing AuNPs. This work represents a foundation for functionalizing AuNPs with VDBA14, and the first step towards point-of-need 25(OH)D3 biosensors.