Study on the biosafety and targeting efficiency of Escherichia coli outer membrane vesicles in breast tumor.

To seek out the targeting of Escherichia coli outer membrane vesicles (E. coli OMVs) in breast tumor-bearing mice and their biosafety in healthy mice. Ultrafiltration in conjunction with ultracentrifugation was utilized to concentrate E. coli OMVs, and characterize them. Subcutaneous breast tumors were induced in BALB/c mice to serve as an experimental model, and the biodistribution of E. coli OMVs in both tumor-bearing and healthy mice was monitored using an in vivo fluorescence imaging system. Utilizing frozen sections, the infiltration of E. coli OMVs in tumor tissues was appraised at the 24-hour post-injection. Healthy BALB/c mice were randomly divided into control group and vesicles group. Following the intravenous injection of E. coli OMVs, monitoring encompassed variations in body weight, blood routine indices, serum levels of AST, ALT, and BUN, organ indices (heart, liver, spleen, lung, and kidney), along with tissue histopathology over a 14-day period. The spherical E. coli OMVs had a diameter of (155.8 ± 3.1) nm and exhibited the expression of outer membrane proteins OmpA and OmpC. Upon assessment, it was evident that the E. coli OMVs persisted in the tumor tissues even 24 h post-injection. An evident decrease in the body weight of the vesicles group, distinct from the control group, was observed on the second day after injection (P < 0.001); in contrast, no considerable differences were noted at subsequent time points (P > 0.05). Following the injection, the vesicles group displayed notable reductions in WBC and PLT as relative to the control group (P < 0.0001) on the initial day, however, there were no noteworthy distinctions as opposed to the control group for other hematological indices; No notable variances in hematological indices between the two groups were observed on the seventh and fourteenth day (P > 0.05). Over the 14 days, no substantial differences were observed in the serum levels of BUN, AST, ALT, and organ indices within the vesicles group as opposed to the control group (P > 0.05). Furthermore, there were no obvious abnormal changes in tissue morphology. 0.5 mg/kg of E. coli OMVs can safely and effectively target 4T1 breast tumor in mice.