An electrochemical aptasensor with N protein binding aptamer-complementary oligonucleotide as probe for ultra-sensitive detection of COVID-19

The emergence of the COVID-19 epidemic has affected the lives of hundreds of millions of people globally. There is no doubt that the development of fast and sensitive detection methods is crucial while the worldwide effective vaccination programs are miles away from actualization. In this study, we have reported an electrochemical N protein aptamer sensor with complementary oligonucleotide as probe for the specific detection of COVID-19. The electrochemical aptasensor was prepared by fixing the double-stranded DNA hybrid obtained by the hybridization of N protein aptamer and its Fc-labeled complementary strand on the surface of a gold electrode. After incubation with the target, the aptamer dissociated from the labeled complementary DNA oligonucleotide hybrid to preferentially bind with N protein in the solution. The concentration of N protein was measured by detecting the changes in electrochemical current signals induced by the conformational transformation of the complementary DNA oligonucleotide left on the electrode surface. The sensor had a linear relationship between the logarithm of the N protein concentration from 10 fM to 100 nM (Delta I-p = 0.098 log C-N protein/fM - 0.08433, R-2 = 0.99), and the detection limitation was 1 fM (S/N = 3). The electrochemical aptamer sensor was applied to test the spiked concentrations of throat swabs and blood samples from three volunteers, and the obtained results proved that the sensor has great potentials for the early detection of COVID-19 in patients.

Automated summary

The COVID-19 epidemic has had a significant impact on the lives of millions of people worldwide. The development of fast and sensitive detection methods is crucial in the absence of effective global vaccination programs. This study presents an electrochemical aptamer sensor for the specific detection of COVID-19, using complementary oligonucleotides as probes. The sensor demonstrated a linear relationship between N protein concentration and electrochemical current signals, with a detection limit of 1 fM. Testing on throat swabs and blood samples from volunteers showed promising results, indicating the sensor's potential for early COVID-19 detection in patients.