Early detection of SARS-CoV-2 with functionalized gold and molecularly imprinted polymeric nanoparticles: a mini review

The novel coronavirus COVID-19 was first reported in Wuhan, China, in December 2019 and rapidly spread to the rest of the world, with the WHO declaring a global pandemic in March 2020. Rapid mutations of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have challenged its diagnosis and treatments. Reverse transcription-polymerase chain reaction (RT-PCR) tests are widely used for the diagnosis of COVID-19; however, they present several drawbacks including high cost, long turnaround time, and need for sophisticated lab infrastructure and trained technical personnel. Lateral flow tests based on antigen sensing are an interesting alternative since they offer rapid (15-30 min) and low-cost analysis, although their low sensitivity has led to several adopted tests being withdrawn from the market. Henceforth, the development of detection methods which are fast, robust, reliable, cost-effective, easy to use and portable is indispensable to prevent community transmission of COVID-19. We have reviewed two different emerging colloidal-based methodologies, (a) functionalized gold nanoparticles (functionalized AuNPs) and (b) molecularly imprinted polymers (MIPs), for fast, highly specific, and reliable identification of SARS-CoV-2. Different modifications of AuNPs with antibodies, antigens and nucleoproteins and their various assays including colorimetric, electrochemical, localized surface plasmon resonance (LSPR) and lateral flow immunoassays are discussed. In contrast, with MIP-based sensors, various antigen proteins and virus particles can be imprinted within the polymeric nanoplatform and hence can be detected with various readout techniques. The operating characteristics of these two emerging diagnostic platforms were critically reviewed and compared against each other.