Assessment of Extracellular Particles from Chlorellae sorokiniana Culture and Suspension of Washed Erythrocytes Concentrated by Ultrafiltration

Extracellular particles (EPs) are sub-micron sized particles found in biological samples containing cells. While the International Society for Extracellular Vesicles (ISEV) recommends assessment with different orthogonal methods, the technologically advanced golden standard methods for harvesting and assessment are sought. Here we report of harvesting and assessment of EPs from two types of samples: suspension of aged, washed erythrocytes and Chlorellae sorokiniana culture. EPs were harvested by reverse ultrafiltration and assessed by Scanning Electron Microscopy (SEM), Interferometric Electron Microscopy (ILM) and UV-vis spectroscopy. We assessed pellets and supernatants of the erythrocyte and microalgae samples (PE, SE, PA, SA, respectively). Average number density of 40 x diluted EPs in PE was (1.160.09) 109/mL and number density of non-diluted EPs in PA was (0.440.02) 109/mL. Average hydrodynamic diameter in SE was (17472) nm, and in PA it was (2527) nm. The supernatants did not present notable amount of EPs. Absorption at 260 nm/280 nm in 4 x diluted SE was (3.680.04)/(2.640.04) arbitrary units (a.u.), in 40 x diluted PE it was (220.2)/(250.0) a.u., in undiluted PA it was (0.310.11)/(0.290.13) a.u. and in undiluted SA it was (0.030.06)/(0.040.01) a.u.. Algae samples contained singular lumps of self-assembly but were poor with proteins and nucleic acids. We conclude that the processing essentially determines the identity of the sample which implies that in order to reach repeatability, the methods should be minimally aggressive to the material, should be made on the same sample and should for this purpose use a minute amount of the sample to enable assessment with other methods. The methods used in this work composed such experimental pipeline that enabled assessment of the samples of in vitro aged erythrocyte EPs and EPs from microalgae culture within hours.