Colorimetric Assay Using Unmodified Gold Nanoparticles for Label-Free Detection of COVID-19
by Nagomi Gopinath
Abstract – In February 2020, the World Health Organization announced the ‘outbreak’ of severe acute respiratory syndrome coronavirus, which causes the respiratory disease, ‘COVID-19’. The present condition is unlike previous situations that occurred with other Coronaviruses, COVID-19 is spreading faster with relatively higher infection- and death- rates, resulting in unusual problems from the lack of proper medicine. Currently, there are two tests in vogue, namely the rapid antibody test and real-time polymerase chain reaction. The former shows a false positive while the latter is expensive and consumes several hours to complete. Researchers are working towards developing a highly sensitive and cheaper diagnosing system for COVID-19. This research was focused on developing a sensitive gold nanoparticle-aptamer mediated colorimetric assay to identify the SARS CoV-2 spike protein S2 (CoV-S2) and the sensing system detects as low as ~109 copies/mL of CoV-S2. The negative control with CoV-S1 and nucleocapsid protein did not show any color changes, indicating the specific detection of CoV-S2. This colorimetric assay helps to identify the lower level of CoV-S2, and discriminates other related proteins, which helps to diagnose COVID-19 at the initial stages of infection.