fa Vaccine vectors, adjuvantsand immunomodulators Vaccine vectors, adjuvantsand immunomodulators Original article Original article <div style="text-align: justify;">Introduction The secretion of extracellular vesicles (EVs) has been neglected in Gram-positive bacteria due to the absence of an outer membrane and the difficulties of proper visualization. Here we aimed to prove that lactobacillus casei can secrete extracellular vesicles. Methods: EVs were extracted from Lactobacillus casei, cultured in De Man, Rogosa and Sharpe broth, using a polyethylene glycol (PEG) solution. The characteristics of the EVs were analyzed by electron microscopy, Dynamic Light Scattering (DLS) and SDS-PAGE. Results: The electron microscopy showed rounded vesicles with average diameter of 300 nm. The protein content of this nanostructure was 2.5 mg/ml with a protein pattern within the range of 10-200 kDa. DLS result showed populations of approximately 300 nm while the extracted EVs had a negative zeta potential. Conclusion: A new method of producing functional molecules from probiotic bacteria was presented. Our results indicated EVs purity with acceptable conformation. Further investigations are necessary to elucidate the efficacy, practicality and mechanism of action of such EVs in clinical practices, especially for development of bio-compounds and vaccine delivery vehicles.</div> Lactobacillus casei, extracellular vesicles, polyethylene glycol. 57 62 http://vacres.pasteur.ac.ir/browse.php?a_code=A-10-1-64&slc_lang=fa&sid=1 M Ebrahimi Vargoorani 0000-0002-4500-9928 No Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran MH Modarressi 0000-0003-2763-1964 No Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran, Iran E Motevaseli 0000-0002-3237-298X No Department of Molecular Medicine, School of Advanced Technologies in Medicine, Tehran University of Medical Sciences, Tehran, Iran. F Vaziri 0000-0001-7788-2548 No Department of Mycobacteriology and Pulmonary Research, Pasteur Institute of Iran, Tehran, Iran. SD Siadat d.siadat@gmail.com 0000-0002-7288-8112 Yes Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.