Gold nanoparticle-modified screen-printed carbon electrodes for label-free detection of SARS-CoV-2 RNA using drop casting and spray coating methods.

BACKGROUND AND PURPOSE

This study aimed to explore the modification of screen-printed carbon electrode (SPCE) to produce an extensive conductive surface with gold nanoparticles (AuNPs) for the detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ribonucleic acid (RNA).

EXPERIMENTAL APPROACH

The experiment was carried out using drop casting (DC) and spray coating (SC) methods. Au-S covalent interactions were formed between thiolated single-stranded DNA (ssDNA) and Au surface, which further hybridized with the target RNA to be detected using differential pulse voltammetry (DPV). Optimization of experimental conditions was performed using Box-Behnken design (BBD) on probe ssDNA concentration, probe ssDNA immobilization time, and target hybridization time. The morphology of the modified electrode was characterized using a scanning electron microscope, while the electrochemical behaviour was determined with DPV and electron impedance spectroscopy.

KEY RESULTS

The results showed that SPCE modification with AuNPs by DC produced a higher peak current height of 12.267 μA with an value of 2.534 kΩ, while SC improved the distribution of AuNPs in the electrode surface. The optimum experimental conditions obtained using BBD were 0.5 μg mL ssDNA-probe concentration, an immobilization time of 22 minutes, and a hybridization time of 12 minutes. The limit of SARS-CoV-2 RNA detection at a concentration range of 0.5 to 10 μg mL was 0.1664 and 0.694 μg mL for DC and SC, respectively. The T-test results for both methods show that the current response of target RNA with SPCE/AuNP by DC does not show the same result, indicating a significant difference in the current response between those two methods.

CONCLUSION

SPCE/AuNP by DC is better than SPCE/AuNP by SC for immobilizing inosine-substituted ssDNA, which subsequently hybridizes with viral RNA, enabling label-free detection of guanine from SARS-CoV-2 RNA.