Kerda Keevend

The silanol content and in vitro cytolytic activity of flame-made silica

HYPOTHESISnThe surface chemistry of synthetic amorphous silicas is essential for their applicational performance and for understanding their interactions with biological matter. Synthesis of silica by flame spray pyrolysis (FSP) allows to control the content and type of hydroxyl groups which also affects the cytolytic activity.nnnEXPERIMENTSnBy controlling the FSP process variables, silica nanoparticles with the same specific surface area but different surface chemistry and content of internal silanols are prepared by combustion of hexamethyldisiloxane sprays, as characterized by Raman and infrared spectroscopy, thermogravimetric analysis, and titration with lithium alanate. Cytolytic activity is assessed in terms of membrane damage in human blood monocytes in vitro.nnnFINDINGSnUnlike commercial fumed silica, FSP-made silicas contain a significant amount of internal silanol groups and a high surface hydroxyl density, up to ∼8OH/nm2, similar to silicas made by wet-chemistry. Increasing the residence time of particles at high temperature during their synthesis reduces the internal and surface hydroxyl content and increases the relative amount of isolated silanols. This suggests incomplete oxidation of the silica matrix especially in short and cold flames and indicates that the silica particle formation pathway involves Si(OH)4. The surface chemistry differences translate into lower cytolytic activity for cold- than hot-flame silicas.

Laser heating of the Y 1-x Dy x PO 4 nanocrystals

We propose a novel material prepared by microwave-hydrothermal treatment, the tetragonal xenotime-type yttrium orthophosphate YPO4 nanocrystals doped by different concentrations of Dy3+. It may be suitable for laser-induced local heating of cancer tumors for hyperthermia. We heated a powder consisted of the nanoparticles by focused quasi-CW laser irradiation at different wavelengths in the near IR spectral range fitting the transparency window of biological tissues. The local temperature on the surface of the powder in the place of irradiation increases linearly with increasing laser power and increasing the Dy3+ concentration. At the same time the efficiency of local heating Φ = ΔT / (P f) (ΔT is a local temperature increase, f is an oscillator strength of absorption transition, and P is the quantity of laser power) is proportional to the energy of the initially excited electronic level. The proposed method allows for high rates of heating and cooling. The laser power used for heating was rather low, tens of milliwatts that together with short heating time to required temperature may result in extremely low doses of laser irradiation for heating.

Removal of Cells from Body Fluids by Magnetic Separation in Batch and Continuous Mode: Influence of Bead Size, Concentration and Contact Time

The magnetic separation of pathogenic compounds from body fluids is an appealing therapeutic concept. Recently, removal of a diverse array of pathogens has been demonstrated using extracorporeal dialysis-type devices. The contact time between the fluid and the magnetic beads in such devices is limited to a few minutes. This poses challenges, particularly if large compounds such as bacteria or cells need to be removed. Here, we report on the feasibility to remove cells from body fluids in a continuous dialysis type of setting. We assessed tumor cell removal efficiencies from physiological fluids with or without white blood cells using a range of different magnetic bead sizes (50-4000 nm), concentrations, and contact times. We show that tumor cells can be quantitatively removed from body fluids within acceptable times (1-2 min) and bead concentrations (0.2 mg per mL). We further present a mathematical model to describe the minimal bead number concentration needed to remove a certain number of cells, in the presence of competing nonspecific uptake. The present study paves the way for investigational studies to assess the therapeutic potential of cell removal by magnetic blood purification in a dialysis-like setting.

An advanced human in vitro co-culture model for translocation studies across the placental barrier

Although various drugs, environmental pollutants and nanoparticles (NP) can cross the human placental barrier and may harm the developing fetus, knowledge on predictive placental transfer rates and the underlying transport pathways is mostly lacking. Current available in vitro placental transfer models are often inappropriate for translocation studies of macromolecules or NPs and do not consider barrier function of placental endothelial cells (EC). Therefore, we developed a human placental in vitro co-culture transfer model with tight layers of trophoblasts (BeWo b30) and placental microvascular ECs (HPEC-A2) on a low-absorbing, 3u2009µm porous membrane. Translocation studies with four model substances and two polystyrene (PS) NPs across the individual and co-culture layers revealed that for most of these compounds, the trophoblast and the EC layer both demonstrate similar, but not additive, retention capacity. Only the paracellular marker Na-F was substantially more retained by the BeWo layer. Furthermore, simple shaking, which is often applied to mimic placental perfusion, did not alter translocation kinetics compared to static exposure. In conclusion, we developed a novel placental co-culture model, which provides predictive values for translocation of a broad variety of molecules and NPs and enables valuable mechanistic investigations on cell type-specific placental barrier function.

ВИЗУАЛИЗАЦИЯ НАНОЧАСТИЦ LaF3, ДОПИРОВАННЫХ Nd3+, ДЛЯ БИОИМИДЖИНГА В БЛИЖНЕМ ИНФРАКРАСНОМ ДИАПАЗОНЕ ПО АП-КОНВЕРСИОННОЙ ЛЮМИНЕСЦЕНЦИИ ПРИ МИКРОСКОПИИ С МУЛЬТИФОТОННЫМ ВОЗБУЖДЕНИЕМ

Ryabova A.V.1, Keevend K.2, Tsolaki E.3, Bertazzo S.3, Pominova D.V.1, Romanishkin I.D.1, Grachev P.V. 1, Makarov V.I.1, Burmistrov I.A.4, Vanetsev A.S.1,6, Orlovskaya E.O.1, Baranchikov A.E.5, R hn M.6, Sildos I.6, Sammelselg V.6, Loschenov V.B.1, Orlovskii Y.V.1,6 General Physics Institute of the Russian Academy of Sciences, Moscow, Russia Swiss Federal Laboratories for Materials Science and Technology (Empa), St. Gallen, Switzerland University College London (UCL), London, United Kingdom Lomonosov Moscow State University, Moscow, Russia Kurnakov Institute of General and Inorganic Chemistry RAS, Moscow, Russia Institute of Physics, University of Tartu, Tartu, EstoniaRecent developments in the field of biophotonics facilitate the raise of interest to inorganic nanoparticles (NPs) doped with Nd 3+ xa0ions, because of their near-infrared (NIR) absorption. These NPs are interesting bioimaging probes for deep tissue visualization, while they can also act as local thermometers in biological tissues. Despite the good possibilities for visualization of NPs with Nd3+xa0ions in NIR spectral range, difficulties arise when studying the cellular uptake of these NPs using commercially available fluorescence microscopy systems, since the selection of suitable luminescence detectors is limited. However, Nd 3+ xa0ions are able to convert NIR radiation into visible light, showing upconversion properties. In this paper we found optimal parameters to excite upconversion luminescence of Nd 3+ +:LaF NPs in living cells and to compare the distribution of the NPs inside the cell culture of human macrophages THP-1 obtained by two methods. Firstly, by detecting the upconversion luminescence of the NPs inVIS under NIR multiphoton excitation using laser scanning confocal microscopy and secondly, using transmission electron microscopy.