Fig. 1.

Design of the SPEEDS platform for detection of IgG and IgM antibodies against SARS-CoV-2 spike protein in human serum. (a) Schematic illustration of the SPEEDS platform and its application scenarios. The platform includes an electrochemical immunosensor and a handheld potentiostat. CE: counter electrode, WE: working electrode, and RE: reference electrode. The potentiostat can transmit testing results to a cell phone. (b) Schematic illustration of surface functionalization of the WE with biotinylated RBD protein as the capture probe. (c) Schematic illustration of capturing anti-SARS-CoV-2 IgG or IgM on the WE and subsequently labelling it with ALP-conjugated detection antibody. (d) Oxidation of the electrochemical substrate (pAPP) during chronoamperometry (CA) and production of the CA current.