Unveiling the Dynamic Mechanism of SARS-CoV-2 Entry Host Cells at the Single-Particle Level

Understanding the dynamic features of severe acute respiratory coronavirus 2 (SARS-CoV-2) binding to the cell membrane and entry cells is crucial for comprehending viral pathogenesis and transmission and facilitating the development of effective drugs against COVID-19. Herein, we employed atomic force microscopy (AFM)-based single-molecule force spectroscopy (SMFS) to study the binding dynamics between the virus and cell membrane. Our findings revealed that the Omicron variant of SARS-CoV-2 virus-like particles (VLPs) exhibited a slightly stronger affinity for the angiotensin-converting enzyme-2 (ACE2) receptor compared with the Delta variant and was significantly higher than the wild-type (WT). Using a real-time force-tracing technique, we quantified the dynamic parameters for a single SARS-CoV-2 VLP entry into cells, showing that approximately 200 ms and 60 pN are required. The parameters aligned with the analysis obtained from coarse-grained molecular dynamics (CGMD) simulations. Additionally, the Omicron variant invades cells at a higher entry cell speed, smaller force, and higher probability. Furthermore, single-particle fluorescence tracking visually demonstrated clathrin-dependent endocytosis for SARS-CoV-2 entry into A549 cells. The dynamic features of endocytosis provide valuable insights into the SARS-CoV-2 entry mechanism and possible intervention strategies targeting the viral infection process.