The Procedure of SP-NLISA for SARS-CoV-2 NP Testing

In total, 100 μL of different concentrations of NP or serum samples (diluted with 0.01 M PBS containing 0.5% Tween, 1% BSA, and 0.01% casein) were added into the freeze-dried microwells contained with a volume of mAb2-MBs and mAb1-Pt@AuNPs. The mixture was reacted for 40 min, and the supernatant was removed by magnets. After washing twice, the microwells were incubated with 100 μL of substrate solution (50% TMB + 50% H₂O₂) for 10 min. Finally, the results were determined by the smartphone-based device.