Tuning the Envelope Structure of Enzyme Nanoreactors for In Vivo Detoxification of Organophosphates

Encapsulated phosphotriesterase nanoreactors show their efficacy in the prophylaxis and post-exposure treatment of poisoning by paraoxon. A new enzyme nanoreactor (E-nRs) containing an evolved multiple mutant (L72C/Y97F/Y99F/W263V/I280T) of Saccharolobus solfataricus phosphotriesterase (PTE) for in vivo detoxification of organophosphorous compounds (OP) was made. A comparison of nanoreactors made of three- and di-block copolymers was carried out. Two types of morphology nanoreactors made of di-block copolymers were prepared and characterized as spherical micelles and polymersomes with sizes of 40 nm and 100 nm, respectively. The polymer concentrations were varied from 0.1 to 0.5% (w/w) and enzyme concentrations were varied from 2.5 to 12.5 μM. In vivo experiments using E-nRs of diameter 106 nm, polydispersity 0.17, zeta-potential -8.3 mV, and loading capacity 15% showed that the detoxification efficacy against paraoxon was improved: the LD50 shift was 23.7xLD50 for prophylaxis and 8xLD50 for post-exposure treatment without behavioral alteration or functional physiological changes up to one month after injection. The pharmacokinetic profiles of i.v.-injected E-nRs made of three- and di-block copolymers were similar to the profiles of the injected free enzyme, suggesting partial enzyme encapsulation. Indeed, ELISA and Western blot analyses showed that animals developed an immune response against the enzyme. However, animals that received several injections did not develop iatrogenic symptoms.

Artificial Microvesicles: New Perspective on Healing Tendon Wounds

Tendons have a limited capacity to repair both naturally and following clinical interventions. Damaged tissue often presents with structural and functional differences, adversely affecting animal performance, mobility, health, and welfare. Advances in cell therapies have started to overcome some of these issues, however complications such as the formation of ectopic bone remain a complication of this technique. Regenerative medicine is therefore looking toward future therapies such as the introduction of microvesicles (MVs) derived from stem cells (SCs). The aim of the present study was to assess the characteristics of artificially derived MVs, from equine mesenchymal stem cells (MSCs), when delivered to rat tendon cells in vitro and damaged tendons in vivo. The initial stages of extracting MVs from equine MSCs and identifying and characterizing the cultured tendon stem/progenitor cells (TSCs) from rat Achilles tendons were undertaken successfully. The horse MSCs and the rat tendon cells were both capable of differentiating in 3 directions: adipogenic, osteogenic, and chondrogenic pathways. The artificially derived equine MVs successfully fused with the TSC membranes, and no cytotoxic or cytostimulating effects were observed. In addition, co-cultivation of TSCs with MVs led to stimulation of cell proliferation and migration, and cytokine VEGF and fractalkine expression levels were significantly increased. These experiments are the first to show that artificially derived MVs exhibited regeneration-stimulating effects in vitro, and that fusion of cytoplasmic membranes from diploid cell lines originating from different species was possible. The experiment in vivo demonstrated the influence of MVs on synthesis of collagen I and III types in damaged tendons of rats. Explorations in vivo showed accelerated regeneration of injured tendons after introduction of the MVs into damaged areas. The results from the studies performed indicated obvious positive modifying effects following the administration of MVs. This represents the initial successful step required prior to translating this regenerative medicine technique into clinical trials, such as for tendon repair in injured horses.

Enzyme Nanoreactor for In Vivo Detoxification of Organophosphates

A nanoreactor containing an evolved mutant of Saccharolobus solfataricus phosphotriesterase (L72C/Y97F/Y99F/W263V/I280T) as a catalytic bioscavenger was made for detoxification of organophosphates. This nanoreactor intended for treatment of organophosphate poisoning was studied against paraoxon (POX). Nanoreactors were low polydispersity polymersomes containing a high concentration of enzyme (20 μM). The polyethylene glycol-polypropylene sulfide membrane allowed for penetration of POX and exit of hydrolysis products. In vitro simulations under second order conditions showed that 1 μM enzyme inactivates 5 μM POX in less than 10 s. LD₅₀-shift experiments of POX-challenged mice through intraperitoneal (i.p.) and subcutaneous (s.c.) injections showed that intravenous administration of nanoreactors (1.6 nmol enzyme) protected against 7 × LD₅₀ i.p. in prophylaxis and 3.3 × LD₅₀ i.p. in post-exposure treatment. For mice s.c.-challenged, LD₅₀ shifts were more pronounced: 16.6 × LD₅₀ in prophylaxis and 9.8 × LD₅₀ in post-exposure treatment. Rotarod tests showed that transitory impaired neuromuscular functions of challenged mice were restored the day of experiments. No deterioration was observed in the following days and weeks. The high therapeutic index provided by prophylactic administration of enzyme nanoreactors suggests that no other drugs are needed for protection against acute POX toxicity. For post-exposure treatment, co-administration of classical drugs would certainly have beneficial effects against transient incapacitation.

Investigation of Gold Electrosorption onto Gold and Carbon Electrodes using an Electrochemical Quartz Crystal Microbalance

The adsorption behavior of Au3+ ions on metal electrodes has been studied using an electrochemical quartz crystal microbalance combined with the cyclic voltammetry technique. The experiments were carried out for HAuCl4 using 0.1 mol·L-1 HCl (pH~1) as a background electrolyte solution. The kinetics of electroreduction of Au3+ ions on the rice husk based activated carbon and gold electrodes in chloride electrolytes by the cyclic voltammetry and the electrochemical quartz crystal microbalance with a variation of the scan rate in the range of 5‒50 mV·s-1 has been studied. The diffusion coefficient of Au3+ ions for the tested solution on gold and carbon electrodes was determined by the cyclic voltammetry method on the basis of the Randles-Ševčik equation. It is found that electroreduction of gold goes via the discharge of AuCl4- complexes to the formation of metallic gold with a current efficiency of 97‒99%. The scanning electron microscopic images of the gold adsorbed carbon surface was taken to see gold particles and their morphology. In SEM images, it is clearly seen that the surface of carbon has a relief structure and gold has grown in the form of clusters. The smallest gold nanoparticles that could be examined were 100‒250 nm in diameter on the surface of the c arbon electrode.

Investigation of Microdiamonds Obtained by the Oxygen-Acetylene Torch Method

The results of experiments on the synthesis of micro- and nano-diamonds by an oxy-acetylene torch on the surface of the pre-deposited copper thin films are presented in this article. The influence of thickness of a buffer copper film and the ratio of the concentrations of oxygen and acetylene on the structure of the deposited samples has been studied in the course of the conducted experiments. The studies by Raman scattering and scanning electron microscopy showed that the synthesis of micro- and nano-diamonds occurs under certain experimental conditions. From the results of the analysis of the obtained samples by the methods of Raman scattering and scanning electron microscopy, it was determined that the deposition time of the copper films and consequently its thickness mainly influence on the structure formation of diamond crystals. On copper films grown for 30 min, the Raman scattering method showed a shift of the diamond peak from the standard (1332 cm‒1) to the low-frequency band (1331.3 cm‒1), which may occur after the presence of stress in the crystals. The results of the investigation showed that with increasing of synthesis time take place smoothing of the facets of crystallites (scanning electron microscopy) and decrease in intensity of the diamond peaks (Raman scattering method).

Investigation of SiC and C Nanostructures Obtained by MWCVD

The results of experiments on the synthesis of SiC and C nanostructures by chemical vapor deposition in microwave plasma are presented in this article. The single crystal silicon plates with orientations [100] and [111] which previously passed chemical purification were used as substrates. Also, the substrates of porous silicon were prepared in order to activate the surface during the synthesis. The synthesis temperature ranged from 700 to 900 °C in steps of 100 °C. The pressure in the chamber was changed depending on the power of the plasma. Studies by scanning electron microscopy (SEM) showed that formed nanostructures have a diameter of 200‒350 nm and a rough surface. The formation of nanostructures on the polished Si occurs on the SiC buffer layer. Analysis of SEM images of the samples shows that growth of NS on the surface of porous silicon is more widespread in contrast to the polished Si. The results of X-Ray spectral microanalysis showed that the carbon content in samples of nanostructures on polished Si varies from 10 to 20% and remains constant on porous silicon ~ 25%. The results of studies by Raman scattering confirmed that SiC film with structure of 3C-SiC is formed on the polished Si. Besides, the presence of main carbon peaks on both types of substrates in the range of 1338.2 and 1583 cm‒1 should be noted, which correspond to the carbon nanostructures.

Magnetization dynamics in magnonic structures with different geometries: interfaces, notches and waveguides

The discovery of ultrafast magnetization dynamics 20 years ago has led to a broad variety of experimental techniques to explore phenomena in magnetic materials with high temporal resolution. In the current article we present a study dealing with broadband excitation of spin-wave packets at different magnonic crystal continuous magnetic film interfaces. Similar to protected conducting states on the surfaces of topological band insulators, these interfaces exhibit surface spin-wave modes that propagate out of the crystal into the continuous film. The propagation distance depends on the direction of the applied magnetic field as well as the surface geometry of the crystal.