Fig. 1.

Preparation and characterization of L. reuteri BBC3-derived EVs (LrEVs). a Phylogenetic diagram of L. reuteri BBC3 based on 16S rRNA sequences. The 15 most homologous sequences in the GenBank database were selected for the construction of a phylogenetic tree. b Representative image of the scanning electron microscope for L. reuteri BBC3 cells showing membrane vesicles on the bacterial cell surface. c Isolation and purification procedures of bacterial EVs. d LrEVs were purified by the discontinuous density ultracentrifugation. Nanoparticle tracking analysis (NTA) was performed to detect the particle numbers of each gradient fraction. Representative images of the scanning electron microscope (e) and transmission electron microscopy (f) for LrEVs. g Representative image from the recorded movies using a SCMOS camera of Malven NTA 3.0 when LrEVs were characterized by NTA. h Concentration and size distribution of the purified LrEVs determined by NTA