Effect of heparin on anti-infection of SARS-CoV-2 pseudovirus and characterization of heparin NPs. (A) hACE2 expression in 293T-hACE2 and 293T cells. (B) Heparin with different molecular weights blocked SARS-CoV-2 infection in 293T-hACE2 cells. LMWH: MW 5600–6400; HMWH: MW 15,000–19,000). Data were normalized by the control group of the SARS-CoV-2 pseudovirus infected 293T-hACE2 cells without treatment. The 293T cells pretreated with heparinase were infected by SARS-CoV-2 pseudovirus (C), and Delta (D) and Delta plus (E) mutated strains. The 293T-hACE2 cells pretreated with heparinase were infected by SARS-CoV-2 pseudovirus (F), Delta (G), and Delta plus (H) mutated strains. (I) Particle size and the cryo-TEM of the NPs. Scale bar: 100 nm. (J) ζ-potential of the NPs. (K) The colloidal stability of the NPs. (L) Size of the pseudovirus. (M) Particle size of the NPs. (N) Size of the NP/pseudovirus complex. (O) The cryo-TEM image of the complex, scale bar: 100 nm. Data are presented as mean ± SD (n = 3); ns, no significance; ∗P < 0.05, ∗∗P < 0.01, ∗∗∗P < 0.001, ∗∗∗∗P < 0.0001.