Applications of gold nanoparticles in virus detection

Draz, Mohamed Shehata; Shafiee, Hadi

Currently, AuNPs have been extensively tested for the immunological and molecular detection of HIV through various scanometric, colorimetric, electrochemical, IPCR, and AFM assays ( Table 1) . The scanometric assays target the detection of the HIV p24 antigen and HIV nucleic acid using the silver metal enhancement protocol. For HIV p24, the target antigen is precaptured by magnetic particles [81] or isolated in a microplate [84] , followed by a silver enhancement step for the quantitative visual immunological detection of HIV (Fig. 4A, B and Fig. 6 ). For HIV nucleic acid detection, AuNP-DNA probes specific to the HIV pol gene are applied to detect HIV nucleic acids precaptured and isolated by magnetic particles, followed by a silver metal enhancement step (Fig. 14A) . The deposition of silver on the AuNP surface increases the NP size and scattering efficiency and additionally allows the target detection via DLS [90] . In AuNP-based colorimetric detection of HIV, the large surface area of AuNPs was exploited to amplify the detection signal by enhancing the gold metal staining on their surfaces, allowing naked-eye detection of HIV nucleic acids (HIV gag gene) in a lateral-flow format, similar to the scheme presented in Fig. 11A [91] . On the other hand, the ability of AuNPs to enhance electron transfer has been applied to develop an electrochemical assay for HIV detection (Fig. 14B) . In this electrochemical assay, the target HIV genome is detected in correlation with the change in electrical impedance of graphene sheets decorated with spherical AuNP-DNA probes specific to the HIV pol gene [73] . The developed AuNP-based RNA detection of HIV using the AuNP-LFA technique has a sensitivity limit of ~11 log10 copies/mL, while the best DNA detection can be achieved through the light-scattering scheme with a sensitivity limit of 10 fM. Furthermore, AFM coupled with AuNPs as nanoparticulate labels has been applied for the detection of HIV p24 as follows: the target antigen is precaptured on the surface of a nanoarray specifically coated with anti-p24 and labeled with AuNP-antibody conjugates that significantly changes the surface topography of the array, allowing the detection of p24 (Fig. 14C) [95] .