Silicon (Si) nanoparticles (NPs) with small (10 À3 -10 À1 at%) content of iron oxide (Fe 2 O 3 ) are prepared by plasma-assisted ablative synthesis. Powders of the prepared Si-iron oxide (SIO) NPs are investigated by means of the transmission electron microscopy, Raman spectroscopy, electron paramagnetic resonance, and magnetic susceptibility measurements. Aqueous suspensions of the NPs are studied by using dynamic light scattering and nuclear magnetic resonance technique. The longitudinal and transverse relaxation times of protons in aqueous suspensions of the NPs are found to be dependent on the iron content. The stronger decrease of the proton relaxation is detected for the samples with higher iron content. Magnetic resonance imaging (MRI) experiments show that SIO NPs have properties of the MRI contrast agent and it is confirmed by in vivo experiments with cancer tumor. Aqueous suspensions of SIO NPs are explored as sensitizers of electromagnetic radio frequency hyperthermia and the highest heating rate is observed for the NPs with smaller hydrodynamic size (%50 nm). The obtained results indicate possible ways for applications of SIO NPs in the MRI diagnostics and mild therapy of cancer.

Multiple studies have demonstrated that various nanoparticles (NPs) stimulate osteogenic differentiation of mesenchymal stem cells (MSCs) and inhibit adipogenic ones. The mechanisms of these effects are not determined. The aim of this paper was to estimate Wharton’s Jelly MSCs phenotype and humoral factor production during tri-lineage differentiation per se and in the presence of silicon–gold NPs. Silicon (SiNPs), gold (AuNPs), and 10% Au-doped Si nanoparticles (SiAuNPs) were synthesized by laser ablation, characterized, and studied in MSC cultures before and during differentiation. Humoral factor production (n = 41) was analyzed by Luminex technology. NPs were nontoxic, did not induce ROS production, and stimulated G-CSF, GM-CSF, VEGF, CXCL1 (GRO) production in four day MSC cultures. During MSC differentiation, all NPs stimulated CD13 and CD90 expression in osteogenic cultures. MSC differentiation resulted in a decrease in multiple humoral factor production to day 14 of incubation. NPs did not significantly affect the production in chondrogenic cultures and stimulated it in both osteogenic and adipogenic ones. The major difference in the protein production between osteogenic and adipogenic MSC cultures in the presence of NPs was VEGF level, which was unaffected in osteogenic cells and 4–9 times increased in adipogenic ones. The effects of NPs decreased in a row AuNPs > SiAuNPs > SiNPs. Taken collectively, high expression of CD13 and CD90 by MSCs and critical level of VEGF production can, at least, partially explain the stimulatory effect of NPs on MSC osteogenic differentiation.

The direct probing and understanding of the dynamics of chemical and biological processes occurring in condensed matter, is currently in its early stages. Progress in this field has been pushed by the development of methods for the study of the structural dynamics of matter in a state far from equilibrium, including extreme states. The forthcoming information serves as the basis for testing new theoretical approaches to the description of the substance in casually connected triad "structure-dynamics-function". Observation of the dynamic behavior of matter in the space-time continuum on ultrashort time scales is a necessary first step in the explanation and, ultimately, control of far from equilibrium processes, and functionality of the systems studied. The method of ultrafast electron crystallography (UEC) makes it possible to investigate transient nonequilibrium structures, which yield decisive information about the structural dynamics of the phase transitions and coherent dynamics of the nuclei in the solid state, on the surface, and in macromolecular systems. In recent years, the electron bunch path length in the UEC apparatus diminished significantly, while the accelerating voltage increased considerably. Therefore, femtosecond electron pulses were obtained. A technique of radio frequency grouping of electrons was proposed to increase the electron pulse brightness. The method of electron field emission was used to increase the spatial coherence, and ponderomotive wave front acceleration was applied to reduce the mismatch between the velocities of the light and electron pulses and to contract the electron bunches. These achievements have opened up new possibilities for studying the coherent structural dynamics – atomic and molecular movie with femtosecond temporal resolution. The results of several internationally renowned research groups are included and cited.

In this paper, it is proposed to use polymer-modified composite materials based on nanocrystalline silicon (nc-Si) as an alternative to organic fluorescent quantum dots traditionally used in medicine. A distinctive feature of nc-Si is a high absorption coefficient in the near UV and blue-violet range and the ability to transmit light in the visible region of the spectrum. The main advantage of silicon-based nanoparticles for in vivo use is their biodegradability and the absence of toxic properties. For hydrophilization of silicon nanoparticles, their surface was modified by amphiphilic biocompatible polymers: polyvinylpyrrolidone, a copolymer of maleic anhydride and 1-octadecene, cremophore, which is a polyoxyethylene derivative of hydrogenated castor oil. Silicon nanoparticles (nc-Si) with an average diameter of 4.5 nm, synthesized by annealing of SiO at 1150 °C, and functionalized with 1-octadecene photoluminescent in the red-infrared spectral region were used. The presence of the polymer shell on the surface of the nanoparticles was confirmed by FTIR spectroscopy. The sedimentation and aggregative stability of the particles in water were analyzed. It is shown that after the nc-Si polymer modification, the photoluminescent properties of nanoparticles are retained although the photoluminesce maxima were shifted to the blue region. Colorimetric MTT-assay of the cytotoxicity of the nanoparticles modified with polymers to monoclonal cells of human erythroleukemia K562 showed no toxicity for cells in culture at a particle concentration of up to 50 μg/ml. Subcellular localization of silicon nanoparticles into the human cervical carcinoma cell line HeLa was shown by means of fluorescence microscopy. The obtained polymer-modified nc-Si particles can be recommended for the purposes of bioimaging in in vitro and in vivo applications.

No abstract