Applications of gold nanoparticles in virus detection

Draz, Mohamed Shehata; Shafiee, Hadi

AuNP-based assays have been developed for the molecular detection of HPV through different photoelectric, fluorometric, electric and colorimetric schemes [89, 98] . The photoelectric assay essentially leverages AuNPs to enhance the deposition of silver metal on their surfaces, as previously described for several other assays. However, the enhanced precipitation of silver metal in this assay is used to block the light generated from a photodiode array (PDA), and the target DNA concentration is measured in proportion to the decrease in light intensity as electrically detected using a bipolar integrated circuit PDA chip [89] . Specifically, PCR-amplified biotinylated target DNA is captured on the surface of the PDA chip, and then labeled with AuNP-biotin antibody conjugates; subsequently, a silver enhancement step decreases the light intensity, which is quantitatively translated into an electrical signal depending on the amount of target DNA (Fig. 13A) . On the other hand, a fluorometric assay integrating AuNPs and a microfluidic bead-based array has been developed as a rapid and controlled HPV DNA detection system [98] . In this assay, AuNPs dually functionalized with HRP enzyme and capture DNA strands are applied to label the target DNA captured on the surface of microbeads (Fig. 4A) , causing HRP to be in proximity to biotin-tyramine loaded on the surface of the microbeads and catalyze their oxidation by hydrogen peroxide. This process eventually increases the deposition of biotin moieties on the surface of the beads, subsequently increasing the labeling efficiency with QD-streptavidin conjugates and yielding an enhanced fluorescence signal that varies significantly based on the target DNA concentration (Fig. 13B) .