Molecular imaging of bacterial outer membrane vesicles based on bacterial surface display

The important roles of bacterial outer membrane vesicles (OMVs) in various diseases and their emergence as a promising platform for vaccine development and targeted drug delivery necessitates the development of imaging techniques suitable for quantifying their biodistribution with high precision. To address this requirement, Semmelweis University researchers aimed to develop an OMV specific radiolabeling technique for positron emission tomography (PET). A novel bacterial strain (E. coli BL21(DE3) ΔnlpI, ΔlpxM) was created for efficient OMV production, and OMVs were characterized using various methods. SpyCatcher was anchored to the OMV outer membrane using autotransporter-based surface display systems. Synthetic SpyTag-NODAGA conjugates were tested for OMV surface binding and 64Cu labeling efficiency. The final labeling protocol shows a radiochemical purity of 100% with a ~ 29% radiolabeling efficiency and excellent serum stability. The in vivo biodistribution of OMVs labeled with 64Cu was determined in mice using PET/MRI imaging which revealed that the biodistribution of radiolabeled OMVs in mice is characteristic of previously reported data with the highest organ uptakes corresponding to the liver and spleen 3, 6, and 12 h following intravenous administration. This novel method can serve as a basis for a general OMV radiolabeling scheme and could be used in vaccine- and drug-carrier development based on bioengineered OMVs.

In vivo biodistribution of radiolabeled outer membrane vesicles

Figure 4

(A) Representative slices of PET/MRI images taken 3, 6, and 12 h after the injection of OMVs labeled using SpT-3-NODAGA. (B) Decay-corrected mean standardized uptake values (SUVmean) of different organs of the same animal. (C) Representative slices of PET/MRI images taken 3, 6, and 12 h after the injection of OMVs labeled using SpT-23-NODAGA. (D) Decay-corrected mean standardized uptake values (SUVmean) of different organs of the same animal.

Szöllősi D, Hajdrik P, Tordai H, Horváth I, Veres DS, Gillich B, Shailaja KD, Smeller L, Bergmann R, Bachmann M, Mihály J, Gaál A, Jezsó B, Barátki B, Kövesdi D, Bősze S, Szabó I, Felföldi T, Oszwald E, Padmanabhan P, Gulyás BZ, Hamdani N, Máthé D, Varga Z, Szigeti K. (2023) Molecular imaging of bacterial outer membrane vesicles based on bacterial surface display. Sci Rep 13(1):18752. [article]

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