Applications of gold nanoparticles in virus detection

Draz, Mohamed Shehata; Shafiee, Hadi

AuNPs have made a tremendous impact in the detection of viruses, as demonstrated by the numerous assays for most of the clinically relevant groups of human viruses (Fig. 3) . Coupled with different biomolecules, AuNPs have enabled the development of a completely new class of probes that are specifically composed of a AuNP core (spherical or rod-like in shape) for signal readout and a surface layer of one or multiple types of biomolecules for target recognition and interaction. These probes have mostly been incorporated as a new set of functional and highly interactive components in different traditional techniques (e.g., EIAs and PCR) and have derived substantial improvements in design, detection performance, sensitivity, specificity and stability. This created a new trend in applying AuNPs to overcome the limitations of traditional techniques. AuNP-based immunological and serological detection methods are the most common and have been accomplished through multiple scanometric, colorimetric, DLS, immuno-PCR, electrochemical, electrical, SERS, LSPR, fluorometric, and AFM-based approaches (Table 1) . AuNP-based DLS and LSPR assays are especially novel, simple and among the most sensitive reported assays for the immunodetection of viruses with a detection limit that is hundreds of times lower than that of the standard ELISA technique [51, 52] . In contrast, the developed AuNP-based molecular assays are not as sensitive as the conventional PCR technique or other PCR-based molecular techniques. However, the addition of AuNPs greatly simplifies the detection procedures of viral nucleic acids, and largely eliminates the need for complex procedures and expensive thermal cycling machines, which greatly reduces the detection time and total cost. In particular, colorimetric assays based on the intense red color of AuNPs represent an interesting qualitative shift in nucleic acid detection due to the complete elimination Magnetic NP (MNP)-DNA probes scavenge target HIV sequences, which are then magnetically collected and labeled with AuNP-DNA probes. After repetitive washing, AuNPs are released into solution by a dehybridization step and subjected to silver metal enhancement, resulting in particle growth and increased scattering [90] . (B) Electrochemical impedance assay of HIV RNA. Graphene oxide sheets decorated with AuNPs are applied for the immobilization of DNA detection probes. Hybridization with specific DNA sequence results in increased impedance [73] . (C) Atomic force microscopy (AFM)-based immunoassay of HIV. AuNP-antibody probes form a three-component sandwich immunocomplex with the target virus antigen captured on the surface of a specific antibody nanoarray; eventually, the increase in the surface height of the array is detected by AFM [95] .