The synthesis, characterization and modification of gold nanoparticles for use in SERS-based COVID-19 antibody testing

Abstract

The current COVID-19 pandemic has highlighted a need for rapid, point-of-care (POC) antibody testing. Antibody testing would allow for a determination of which members of the population have already been infected with the SARS-CoV-2 virus, and also which members have built up sufficient immunity after vaccination. Current POC diagnostic platforms which screen for antibodies in bodily fluids are typically either lateral flow or vertical flow based, and make use of labelled colloidal gold, which exhibits a red colour, as the visual interpretation for the test. In this thesis work, we are seeking to use the colloidal gold in these platforms as the enhancing element in surface-enhanced Raman spectroscopy (SERS) which would make such tests not only qualitative but also quantitative. For SARS-CoV-2 infections, this means that antibody levels could be monitored over time, which would be very useful. In this work, colloidal gold nanoparticles (AuNP) were synthesized, characterized and modified for use in such rapid test platforms. The AuNPs of varying diameters were characterized using UV-Vis and scanning electron microscopy. The SERS performance of the AuNPs was ascertained using a probe molecule as a tag. The AuNPs were modified with a capture agent and the SERS tag components, and were explored for use in a flow assay prototype. These results indicate that modified AuNPs in conjunction with SERS may be useful for quantitative readouts for COVID-19 antibody testing platforms.