Proteomic and Physicochemical Analysis of Erythrocyte Membrane Vesicles from Fresh and Frozen Blood

Abstract

Erythrocyte membrane vesicles (EMVs) have emerged as promising nanocarriers for drug delivery due to their biocompatibility and immune evasion through retention of erythrocyte surface proteins. The main limitation is their dependence on freshly drawn blood, which limits batch production. Long-term storage of EDTA-anticoagulated blood at −80°C without cryoprotectant represents an accessible alternative, but its effect on EMV physicochemical properties and protein composition has not been investigated. We prepared EMVs from fresh and frozen blood and characterized the resulting fractions by dynamic light scattering, nano-flow cytometry, cryo-transmission electron microscopy, negative staining transmission electron microscopy, and quantitative mass spectrometry-based proteomics. EMV size, surface charge, and morphology did not differ significantly between fresh and frozen preparations. Extrusion effectively normalized particle size despite increased heterogeneity in frozen ghost cell fractions, and both preparations yielded structurally intact vesicles after ultracentrifugation. At the proteomic level, freezing reduced proteomic complexity in membrane fractions and selectively depleted cytosol-associated proteins. The core membrane proteome, including Band 3, remained stable. However, glycophorin A showed the largest reduction in frozen preparations, and CD47 levels were reduced in the ultracentrifuged fraction. These differences may be critical for applications where preservation of specific surface proteins is required, such as immune evasion or targeted drug delivery. In some cases, frozen blood is potentially a viable source for EMV production when immediate processing is not feasible.