Elisa femto substrate

Wells of a white streptavidin-coated 96-well plate (Thermo Fisher Scientific) were washed and blotted three times with SELEX WB then incubated with 50 nM biotinylated NS or SNAP1 aptamer at 4°C for 30 min. After three washes with wash buffer (0.1% Tween-20 2% BSA SELEX), wells were incubated with blocking buffer (5% BSA, 1:100 biotin blocking solution (Vector Laboratories), 0.1 mg/mL tRNA, 0.1 mg/mL SS DNA, 0.1% Tween-20 SELEX WB) for 1.5 h at room temperature. Subsequently, the wells were incubated with S protein, UV-inactivated SARS-CoV-2 virus, or lentivirus in binding buffer (2% BSA, 0.1 mg/mL tRNA, 0.1 mg/mL SS DNA, 0.1% Tween-20 SELEX WB) for 30 min at room temperature. Then wells were washed four times before incubation with an anti-SARS-CoV-2 antibody with HRP (Novus Biologicals cat. no. NBP2–90980H). Lastly, wells were washed six times. All steps use 100 μL of the solution, except washing (200 μL of solution.) For wash steps, the plate is flicked over a sink then blotted dry. Ice-cold ELISA Femto Substrate (Thermo Fisher Scientific) was added, and the plate luminescence was immediately measured by Infinite 200 PRO plate reader (Tecan) with 250 nm integration time and automatic attenuation.