An electrochemical microsensor of the SARS-CoV-2 nucleocapsid protein based on surface-imprinted acupuncture needle

A novel electrochemical microsensor is constructed on a traditional acupuncture needle (AN) and used to monitor a biomarker of the SARS-CoV-2-N protein. The reversible interaction of the borate bond between the cis-diol in this glycoprotein and the phenylboronic acid in 4-mercaptophenylboronic acid (4-MPBA) is effectively exerted. This interaction was applied to anchor the SARS-CoV-2-N protein onto 4-MPBA, which is covalently self-assemblied onto electrodeposited AuNPs by the S-Au bond. Meldola blue was then electropolymerized around the protein template. After the template was eluting, three-dimensional nanocavities complementary with the protein were generated within the polymelola blue (pMB) layer. Interestingly, nanocavities could play a channel role for the electron-transfer of outer [Fe(CN)6]3−/4−, and the signal of electrochemical probe could be hindered after recombining the SARS-CoV-2-N protein, which laid a platform for the detection of this biomarker. After optimizing the influencing factors, the prepared microsensor exhibits a linear range of 0.1 ~ 1000 ng mL−1 with a low detection limit of 0.01 ng mL−1 (S/N = 3). In particular, the sensing ability was dramatically affected by the thickness correlative factors for the polymer matrix. The suitable thickness is effective for the sensing signals, which corresponds to the behavior of surface-imprinted polymer. The microsensor showed comparatively high sensitivity and selectivity and practically detected the SARS-CoV-2-N protein in the serum sample, which is of scientific significance for the development of the electrochemical microsensor and acupuncture.