Law of corresponding states for osmotic swelling of vesicles

As solute molecules permeate into a vesicle due to a concentration difference across its membrane, the vesicle swells through osmosis. The swelling can be divided into two stages: (a) an "ironing" stage, where the volume-to-area ratio of the vesicle increases without a significant change in its area; (b) a stretching stage, where the vesicle grows while remaining essentially spherical, until it ruptures. We show that the crossover between these two stages can be represented as a broadened continuous phase transition. Consequently, the swelling curves for different vesicles and different permeating solutes can be rescaled into a single, theoretically predicted, universal curve. Such a data collapse is demonstrated for giant unilamellar POPC vesicles, osmotically swollen due to the permeation of urea, glycerol, or ethylene glycol. We thereby gain a sensitive measurement of the solutes' membrane permeability coefficients, finding a concentration-independent coefficient for urea, while those of glycerol and ethylene glycol are found to increase with solute concentration. In addition, we use the width of the transition, as extracted from the data collapse, to infer the number of independent bending modes that affect the thermodynamics of the vesicle in the transition region.Comment: 10 page

Hybridosomes from spruce needle homogenate

Introduction: Being of compatible structure with biomembranes, lipid–based nanoparticles are considered as convenient platforms for drug delivery systems. In the proposed work we considered formation of lipid nanovesicles associated with bioactive phytochemicals from spruce needle homogenate (here called hybridosomes). We formed hybridosomes by mixing appropriate amounts of lecithin, supernatant of isolation of extracellular particles from spruce needle homogenate and glycerol. Methods: We visualized hybridosomes by light microscopy and cryogenic transmission electron microscopy and assessed them by flow cytometry, dynamic light scattering, ultraviolet–visual spectroscopy and interferometric microscopy. Results: We found that the particles consisted of a bilayer membrane and a fluid-like interior. Flow cytometry and interferometric light microscopy measurements showed that the majority of the particles were nano-sized. Dynamic light scattering and interferometric light microscopy measurements agreed well with the determined average hydrodynamic radius of the particles Rh (between 140 and 180 nm) while their number densities were in the range between 10^13 and 10^14/mL indicating that hybridosomes present about 2/3 of the mixture, excluding solvent and other small molecules. Discussion: Simple and low-cost preparation method, non-demanding saving process and efficient formation procedure suggest that large scale production of hybridosomes from lipids and spruce needle homogenate is feasible.Small New World 2.0 4-5 September 2023., Graz, Austri

Hybridosomes from spruce needle homogenate

Introduction: Being of compatible structure with biomembranes, lipid–based nanoparticles are considered as convenient platforms for drug delivery systems. In the proposed work we considered formation of lipid nanovesicles associated with bioactive phytochemicals from spruce needle homogenate (here called hybridosomes). We formed hybridosomes by mixing appropriate amounts of lecithin, supernatant of isolation of extracellular particles from spruce needle homogenate and glycerol. Methods: We visualized hybridosomes by light microscopy and cryogenic transmission electron microscopy and assessed them by flow cytometry, dynamic light scattering, ultraviolet–visual spectroscopy and interferometric microscopy. Results: We found that the particles consisted of a bilayer membrane and a fluid-like interior. Flow cytometry and interferometric light microscopy measurements showed that the majority of the particles were nano-sized. Dynamic light scattering and interferometric light microscopy measurements agreed well with the determined average hydrodynamic radius of the particles Rh (between 140 and 180 nm) while their number densities were in the range between 10^13 and 10^14/mL indicating that hybridosomes present about 2/3 of the mixture, excluding solvent and other small molecules. Discussion: Simple and low-cost preparation method, non-demanding saving process and efficient formation procedure suggest that large scale production of hybridosomes from lipids and spruce needle homogenate is feasible.Small New World 2.0 4-5 September 2023., Graz, Austri

Electroformation in a flow chamber with solution exchange as a means of preparation of flaccid giant vesicles

A recently described technique (Estes and Mayer, Biochim. Biophys. Acta 1712 (2005) 152--160) for the preparation of giant unilamellar vesicles (GUVs) in solutions with high ionic strength is examined. By observing a series of osmotic swellings followed by vesicle bursts upon a micropipette transfer of a single POPC GUV from a sucrose solution into an isoosmolar glycerol solution, a value for the permeability of POPC membrane for glycerol, P = (2.09+/-0.82) x 10^{-8} m/s, has been obtained. Based on this result, an alternative mechanism is proposed for the observed exchange of vesicle interior. With modifications, the method of Estes and Mayer is then applied to preparation of flaccid GUVs.Comment: 13 pages, 10 figures, accepted for publication in Colloids and Surfaces B: Biointerface

Characterization of Nanohybridosomes from Lipids and Spruce Homogenate Containing Extracellular Vesicles

Introduction: Lipid nanovesicles associated with bioactive phytochemicals from spruce needle homogenate (here called nano-sized hybridosomes or nanohybridosomes, NSHs) were considered. Methods: We formed NSHs by mixing appropriate amounts of lecithin, glycerol and supernatant of isolation of extracellular vesicles from spruce needle homogenate. We visualized NSHs by light microscopy and cryogenic transmission electron microscopy and assessed them by flow cytometry, dynamic light scattering, ultraviolet–visual spectroscopy, interferometric light microscopy and liquid chromatography–mass spectrometry. Results: We found that the particles consisted of a bilayer membrane and a fluid-like interior. Flow cytometry and interferometric light microscopy measurements showed that the majority of the particles were nano-sized. Dynamic light scattering and interferometric light microscopy measurements agreed well on the average hydrodynamic radius of the particles Rh (between 140 and 180 nm), while the concentrations of the particles were in the range between 1013 and 1014/mL indicating that NSHs present a considerable (more than 25%) of the sample which is much more than the yield of natural extracellular vesicles (EVs) from spruce needle homogenate (estimated less than 1%). Spruce specific lipids and proteins were found in hybridosomes. Discussion: Simple and low-cost preparation method, non-demanding saving process and efficient formation procedure suggest that large-scale production of NSHs from lipids and spruce needle homogenate is feasible. Plain Language Summary: Cells shed into their exterior nanoparticles (here referred to as extracellular vesicles – EVs) that are free to move, reach distant cells and are taken up by them. As they carry bioactive constituents, EVs may have important impact on the recipient cells. The mechanisms of EV formation and mediation can be employed in designing therapeutic, prophylactic and diagnostic methods for various medical issues. EVs can be harvested from biological samples; however, their yield is small,12 and there are potential side effects. Artificial vesicles – liposomes – have high yield; however, in vivo, they can be degraded before reaching the target and their reproducibility is yet insufficient. In order to combine advantages of both types of nanoparticles, we have composed nanohybridosomes (NSHs) from soya lecithin, water and supernatant of isolation of EVs from spruce needle homogenate, visualized them by cryogenic electron microscopy and characterized them with respect to their size, concentration and protein/nucleic acid content. We have applied a recently developed interferometric light microscopy to determine the hydrodynamic radius and the concentration of EVs. We found that the majority of composed particles are nano-sized and that they enclose more than 25% of the incoming volume of liquid, which is considerably more than about 1% that can be harvested by isolation of EVs from spruce needle homogenate by (ultra) centrifugatio

Assessment of small cellular particles from four different natural sources and liposomes by interferometric light microscopy

Small particles in natural sources are a subject of interest for their potential role in intercellular, inter-organism, and inter-species interactions, but their harvesting and assessment present a challenge due to their small size and transient identity. We applied a recently developed interferometric light microscopy (ILM) to assess the number density and hydrodynamic radius (Rh) of isolated small cellular particles (SCPs) from blood preparations (plasma and washed erythrocytes) (B), spruce needle homogenate (S), suspension of flagellae of microalgae Tetraselmis chuii (T), conditioned culture media of microalgae Phaeodactylum tricornutum (P), and liposomes (L). The aliquots were also assessed by flow cytometry (FCM), dynamic light scattering (DLS), ultraviolet-visible spectrometry (UV-vis), and imaging by cryogenic transmission electron microscopy (cryo-TEM). In Rh, ILM showed agreement with DLS within the measurement error in 10 out of 13 samples and was the only method used here that yielded particle density. Cryo-TEM revealed that representative SCPs from Tetraselmis chuii flagella (T) did not have a globular shape, so the interpretation by Rh of the batch methods was biased. Cryo-TEM showed the presence of thin filaments in isolates from Phaeodactylum tricornutum conditioned culture media (P), which provides an explanation for the considerably larger Rh obtained by batch methods than the sizes of particles observed by cryo-TEM images. ILM proved convenient for assessment of number density and Rh of SCPs in blood preparations (e.g., plasma)therefore, its use in population and clinical studies is indicated