A polyethylene glycol-based method for extraction of extracellular vesicles from Lactobacillus casei as vaccine delivery vehicle

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.