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Vesna Spasovski,1,2,* Anna Romolo,1,3,* Urška Zagorc,4 Vesna Arrigler,4 Matic Kisovec,5 Apolonija Bedina Zavec,5 Matevž Arko,1 Adrienn Molnár,6,7 Gitta Schlosser,7 Aleš Iglič,3,8 Ksenija Kogej,4 Veronika Kralj-Iglič1 1University of Ljubljana, Faculty of Health Sciences, Laboratory of Clinical Biophysics, Ljubljana, Slovenia; 2Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Belgrade, Serbia; 3University of Ljubljana, Faculty of Electrical Engineering, Laboratory of Physics, Ljubljana, Slovenia; 4University of Ljubljana, Faculty of Chemistry and Chemical Technology, Ljubljana, Slovenia; 5National Institute of Chemistry, Department of Molecular Biology and Nanobiotechnology, Ljubljana, Slovenia; 6Hevesy György PhD School of Chemistry, ELTE Eötvös Loránd University, Budapest, Hungary; 7MTA-ELTE Lendület Ion Mobility Mass Spectrometry Research Group, Faculty of Science, Institute of Chemistry, ELTE Eötvös Loránd University, Budapest, Hungary; 8University of Ljubljana, Faculty of Medicine, Laboratory of Clinical Biophysics, Ljubljana, Slovenia*These authors contributed equally to this workCorrespondence: Veronika Kralj-Iglič, Email veronika.kralj-iglic@zf.uni-lj.siIntroduction: 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)centrifugation.Keywords: hybridosomes, liposomes, nanovesicles, extracellular particles, small cellular particles, drug delivery

Objectives: Ketamine exerts rapid antidepressant effects by enhancing neuroplasticity, particularly in the amygdala and hippocampus—regions involved in fear processing and learning. While the role of ketamine's dissociative effects in its antidepressant response is debated, anxiety experienced during infusion has been negatively correlated with treatment outcomes. Methods: In this single-blind, placebo-controlled study, a subset of 17 healthy volunteers (6 males, 23.12 ± 1.9 years) received intravenously a placebo in the first and 0.5 mg/kg racemic ketamine in the second session. Anxiety-related experiences were assessed by the 5D-ASC score obtained post-infusion, structural magnetic resonance imaging scans were acquired 4 h post-infusion. An anxiety-score was obtained from the 5D-ASC. Relation between post-placebo amygdala volume, hippocampal volume, and its subfields with the anxiety-score were assessed using linear regression models. Results: Results showed a statistically significant negative relation between hippocampal head volume and the anxiety score (β = −0.733, p = 0.006), with trending negative association for each subfield's head and the score. Conclusion: These findings suggest that anxiety-related experiences during ketamine infusion may be mediated by the hippocampus, with smaller hippocampal volumes leading to more anxiety-related experiences. Thus, hippocampal subfield volumes may be used as a predictor for anxiety-related events during ketamine use and might predict treatment outcome in future approaches. [ABSTRACT FROM AUTHOR]