Objective  To prepare hemoglobin-bovine serum albumin nanoparticles with red blood cell membrane directional coating (RBC-Hb/BSA-NP) and to evaluate their physicochemical properties and long circulation capability.

  Methods  The bovine serum albumin nanoparticles modified with human hemoglobin (Hb/BSA-NP) were prepared by the solvent evaporation method. Then, the red blood cell (RBC) membrane was coated on the surface of Hb/BSA-NP by applying physical extrusion. The particle size, zeta potential and morphology of the resulting RBC-Hb/BSA-NP were characterized. The optimal amount of RBC membrane was determined by evaluating the integrity of the RBC membrane coating on RBC-Hb/BSA-NP, while the orientation of the RBC membrane was determined by measuring the content of sialic acid content on the surface of the RBC-Hb/BSA-NP. The anti-phagocytosis ability against macrophage of the RBC-Hb/BSA-NP was evaluated with fluorescence microscope and flow cytometry in vitro , and the long circulation capability of the nanoparticles was assessed through pharmacokinetic experiment in vivo.

  Results  The RBC-Hb/BSA-NP showed an average size of (127.7±3.5) nm, a zeta potential of (−17.1±0.28) mV, a clear core-shell structure and good stability within 72 h. The RBC membrane extracted from 0.8 mL of whole blood can completely coat 1 mL of Hb/BSA-NP (ρ_BSA=10 mg/mL). The content of sialic acid on the RBC-Hb/BSA-NP was comparable to that of natural red blood cells without significant change, indicating the correct orientation of RBC membranes on the surface of the nanoparticles. Compared with regular BSA nanoparticles, RBC-Hb/BSA-NP could significantly reduce the uptake in macrophages, and it’s circulation time in vivo was greatly prolonged.

  Conclusion  RBC-Hb/BSA-NP was successfully constructed, and it was shown that the delivery system had prolonged circulation time.