1 © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.com In vivo Kinetic Biodistribution of Nano-Sized Outer Membrane Vesicles Derived from Bacteria Su Chul Jang, Sae Rom Kim, Yae Jin Yoon, Kyong-Su Park, Ji Hyun Kim, Jaewook Lee, Oh Youn Kim, Eun-Jeong Choi, Dae-Kyum Kim, Dong-Sic Choi, Yoon-Keun Kim, Jaesung Park, Dolores Di Vizio,* and Yong Song Gho* 1. Introduction Nanoparticles have been extensively studied in the field of materials, toxicology, and drug delivery due to their unique physicochemical properties. [1–3] Together with various DOI: 10.1002/smll.201401803 Evaluation of kinetic distribution and behaviors of nanoparticles in vivo provides crucial clues into their roles in living organisms. Extracellular vesicles are evolutionary conserved nanoparticles, known to play important biological functions in intercellular, inter- species, and inter-kingdom communication. In this study, the first kinetic analysis of the biodistribution of outer membrane vesicles (OMVs)—bacterial extracellular vesicles— with immune-modulatory functions is performed. OMVs, injected intraperitoneally, spread to the whole mouse body and accumulate in the liver, lung, spleen, and kidney within 3 h of administration. As an early systemic inflammation response, increased levels of TNF-α and IL-6 are observed in serum and bronchoalveolar lavage fluid. In addition, the number of leukocytes and platelets in the blood is decreased. OMVs and cytokine concentrations, as well as body temperature are gradually decreased 6 h after OMV injection, in concomitance with the formation of eye exudates, and of an increase in ICAM-1 levels in the lung. Following OMV elimination, most of the inflammatory signs are reverted, 12 h post-injection. However, leukocytes in bronchoalveolar lavage fluid are increased as a late reaction. Taken together, these results suggest that OMVs are effective mediators of long distance communication in vivo. Outer Membrane Vesicles Dr. S. C. Jang, S. R. Kim, Dr. K.-S. Park, Dr. J. H. Kim, J. Lee, O. Y. Kim, Dr. E.-J. Choi, D.-K. Kim, Dr. D.-S. Choi, Prof. Y.-K. Kim, Prof. Y. S. Gho Department of Life Sciences Pohang University of Science and Technology Pohang 790–784, Republic of Korea E-mail: ysgho@postech.ac.kr Prof. D. Di Vizio Division of Cancer Biology and Therapeutics Samuel Oschin Comprehensive Cancer Institute Cedars-Sinai Medical Center Los Angeles, California 90048, USA E-mail: Dolores.Divizio@cshs.org Dr. Y. J. Yoon Division of Integrative Biosciences and Biotechnology Pohang University of Science and Technology Pohang 790–784, Republic of Korea Prof. J. Park Department of Mechanical Engineering Pohang University of Science and Technology Pohang 790–784, Republic of Korea nanoparticles that are artificially synthesized using sophisti- cated materials, naturally produced biological nanoparticles, called extracellular vesicles (EVs), are emerging candidates with strong clinical potential including in vaccine, diagnosis, small 2014, DOI: 10.1002/smll.201401803