2.3. ACE2-HEK293T/cell membrane chromatography (CMC)

The CMC refers to making the cell membrane into a stationary phase and then using HPLC to study the interaction of drug and membrane receptor, which can mimic the binding of drug and receptor in vivo (^{Han et al., 2018}). ACE2-HEK293T/CMC columns (n = 3) were prepared with ACE2-HEK293T cells following the published protocol (^{Hou et al., 2009}). The CMC screening was performed via LC-30A (Shimadzu, Japan). Various histamine H₁ receptor antagonists dissolved with methanol were injected into the ACE2-HEK293T/CMC column, respectively. ACE2-HEK293T/CMC column 10.0 mm × 2.0 mm, flow rate 0.2 ml/min, column temperature 37 °C, mobile phase 2 mM phosphate-buffer saline (pH 7.4), detection wavelength 254 nm. Components with retention characteristics on ACE2-HEK293T/CMC columns were considered capable of combining ACE2.