Applications of gold nanoparticles in virus detection

Draz, Mohamed Shehata; Shafiee, Hadi

Several AuNP-based electrochemical assays have been developed for the detection of HBV antigens and DNA. Two enzyme-amplified electrochemical assays have been reported for the detection HBV surface antigen (HBsAg) using conjugates of AuNPs and horseradish peroxidase (HRP)-labeled antibodies against HBV surface antigen (HBsAbs) [76, 77] . The target HBsAg is captured and labeled with AuNP-HBsAb/HRP as secondary antibody conjugates. Then the reduction of H2O2 catalyzed by the bound HRP is measured either by using an AuNP/thionin/DNA-modified Au electrode coupled with a cyclic voltammeter [76] or through using a nanoporous Au electrode coupled with differential pulse voltammeter [77] (Fig. 9A) . Alizadeh et al. reported AuNPs modified with horseradish peroxidase mimicking DNAzyme to label HBsAg magnetically captured and concentrated on the surface of a Au sheet-like electrode. Due to the efficient catalytic activity of HRP-mimicking DNAzyme, the proposed immunoassay allowed quantitative detection of HBsAg with a linear concentration range of 0.3-1000 pg/mL and detection limit of 0.19 pg/mL [15] . Other studies described the electrochemical detection of HBV based on AuNP-metal enhancement amplification, including copper and silver metal enhancement [74, 75] . Using copper metal enhancement, HBsAg is sandwiched by MNP-HBsAb conjugates and AuNP-HBsAb probes to form a 3-component immunocomplex, which is magnetically separated and stained through a copper enhancement step (Fig. 9B ). After copper acidic dissolution, the resulting ions are measured by anodic stripping voltammetry (ASV) [75] . Using silver enhancement, HBV DNA is detected using probes prepared of streptavidin-modified AuNPs. Biotinylated HBsAg gene sequences are magnetically pre-separated and concentrated using magnetic bead-DNA conjugates. The deposited silver ions are then analyzed by an electrochemical stripping technique to detect the target HBV DNA quantitatively [74] .