Stem Cell Exosomes Improve Survival of Neural Stem Cells after Radiation Exposure.

The death of neural stem cells in the hippocampus during radiation therapy of brain tumors leads to neurogenesis impairment and the development of cognitive dysfunctions at delayed terms after irradiation. Exosomes secreted by stem cells can provide a protective effect on neural stem cells. We isolated and characterized exosomes from the medium conditioned by neural stem cells and mesenchymal stem cells from mouse adipose tissue and studied their efficiency in protecting irradiated neural stem cells. According to dynamic light scattering data, the exosome size varied from 44 to 68 nm for neural stem cells, and from 80 to 130 nm for mesenchymal stem cells. All exosomes carried markers CD9, CD63, and TSG101. The survival rate and clonogenic activity of neural stem cells irradiated in a dose of 1 Gy was found to increase after culturing in the presence of stem cell exosome preparations.

Low-filled suspensions of α-chitin nanorods for electrorheological applications.

Highly anisometric α-chitin nanoparticles isolated by TEMPO-oxidation were investigated as filler for electrorheological fluids. The dimensions of rod-like particles were determined by AFM and cryo-TEM methods. The rheological behavior of α-chitin nanoparticles in polydimethylsiloxane changes from viscous to elastic under electric field. The yield stress reaches about 220 Pa at 7 kV/mm for 1.0 wt% fluid. Despite the nanosize of particles, the suspensions sedimentation ratio was found to be low (~23%). The electrorheological behavior of the fluids was discussed in terms of the Mason numbers. The stability of fluids response under switching electric field was shown. The activation energy of polarization processes in suspensions was calculated as 58 ± 2 and 64 ± 1 kJ/mol for 0.5 and 1.0 wt% filler content from the impedance spectra. The high aspect ratio (~70) and dielectric permittivity result in high electrorheological activity of α-chitin suspensions at extremely low concentrations (≤1.0 wt%).

Enhanced electrorheological activity of porous chitosan particles.

Novel porous filler for electrorheological fluids was fabricated from chitosan via freeze drying technique. An exceptional electrorheological effect was discovered in suspensions of polydimethylsiloxane (silicone oil) filled by highly porous chitosan particles. The electrorheological activity was studied by rotational rheometry and visualized by optical microscopy. High porosity of the filler allows preparing highly efficient electrorheological fluids at rather low (< 1 wt%) concentration of dispersed phase. The mechanism of chain-like structure formation was considered. The electrorheological behavior of suspensions and the filler structural organization at different concentration were comprehended in terms of dielectric properties. The rheological data were approximated by Bingham and Cho-Choi-Jhon equations. The sedimentation stability of chitosan suspensions in polydimethylsiloxane was significantly affected by particles porosity.

Efficient screening of ligand-receptor complex formation using fluorescence labeling and size-exclusion chromatography.

Evidence of a complex formation is a crucial step in the structural studies of ligand-receptor interactions. Here we presented a simple and fast approach for qualitative screening of the complex formation between the chimeric extracellular domain of the nicotinic acetylcholine receptor (α7-ECD) and three-finger proteins. Complex formation of snake toxins α-Bgtx and WTX, as well as of recombinant analogs of human proteins Lynx1 and SLURP-1, with α7-ECD was confirmed using fluorescently labeled ligands and size-exclusion chromatography with simultaneous absorbance and fluorescence detection. WTX/α7-ECD complex formation also was confirmed by cryo-EM. The proposed approach could easily be adopted to study the interaction of other receptors with their ligands.

Effect of exfoliating agent on rheological behavior of ß-chitin fibrils in aqueous suspensions and on mechanical properties of poly(acrylic acid)/ß-chitin composites.

Chitin whiskers are promising reinforcing filler for composites due to their mechanical properties, renewable nature and low cost. A new method for preparation of ß-chitin fibrils from squid pens in ascorbic acid aqueous solutions (AscA) was developed. Stirring of the solution with 2 g/l AscA for 2 h disperses the swollen chitin to individualized fibrils with an aspect ratio > 250. The optimal conditions of ß-chitin exfoliation in acrylic acid (AcrA) aqueous solution were found (0.75-2 g/l, 3-4 h). TEMPO-oxidized ß-chitin fibrils were chosen as a reference sample for comparison of different methods. 0.1% chitin suspensions exfoliated in AscA and AcrA solutions show similar gel-like behavior with a storage modulus (G') of 98 ±â€¯23 and 34 ±â€¯12 Pa, respectively, whereas G' of 0.1% dispersion of the TEMPO-oxidized ß-chitin fibrils was 0.015 ±â€¯0.005 Pa only. Composites based on poly(acrylic acid) comprising 1-3 wt% of ß-chitin fibrils were fabricated by polymerization filling. Mechanical properties of the composites were investigated in dry state in the temperature range of 25-250 °C and at controlled relative humidity in the range from 53.6% to 100%. It was revealed that the maximum reinforcing effect is achieved at high temperature (>120 °C) and high relative humidity (≥75.3%RH).

[Isolation of extracellular micro-vesicles from cell culture medium: comparative evaluation of methods]. / Sravnitel'nyi analiz metodov vydeleniia vnekletochnykh mikrovezikul iz kul'tural'noi sredy.

Extracellular vesicles (EV) are secreted by cells of multicellular organisms. EV mediate specific mode of intercellular communication by "horizontal" exchange of substances and information. This phenomenon seems to have an essential biological significance and became a subject of intensive research. Biogenesis, structural and functional features of the EV is being commonly studies in in vitro condition. Several methods of EV isolation from cell culture medium are established, however selection of method might influence on obtained results. The choice of the optimal method depends usually from the amount of medium and the aims of the research while is still challenging issue. We performed a comparative analysis of four different methods of EV isolation from cell culture medium: differential ultracentrifugation, ultracentrifugation with a 30% sucrose/D2O "cushion", precipitation with plant proteins and immune-affinity capturing. EV isolated by different approaches were compared in terms of following parameters: size, concentration, morphology of EV, contamination by non-vesicular particles, content of exosomal tetraspanins on the EV surface, content of total proteins, RNA, and several glioma-associated miRNAs. Applied methods included nano-patricle tracking analysis (NTA), dynamic light scattering (DLS), cryo-electron microscopy, flow cytometry and RT-qPCR. On the base of obtained results, we developed practical recommendations that may help researchers to make a best choice of EV isolation method.