Oxidative damage to ßL-crystallin in vitro by iron compounds formed in physiological buffers.

ßL-crystallin aggregation due to oxidative damage in the presence of H2O2 and ferric chloride was studied in-vitro under conditions close to physiological. It was shown that the protein aggregation characterized by the nucleation time and the aggregation rate significantly depended on the composition of the isoosmotic buffers used, and decreased in the series HEPES buffer > Tris buffer > PBS. Ferric chloride at neutral pH was converted into water-insoluble iron hydroxide III (≡FeIIIOH). According to the data of scanning electron microscopy the ≡FeIIIOH particles formed in HEPES buffer, Tris buffer, and PBS practically did not differ in structure. However, the sizes of ≡FeIIIOH floating particles measured by dynamic light scattering differed significantly and were 44 ± 28 nm, 93 ± 66 nm, 433 ± 316 nm (Zaver ± SD) for HEPES buffer, Tris buffer, and PBS, respectively. It was found by the spin trap method that the ability of ≡FeIIIOH to decompose H2O2 with the formation of a •OH decreases in the series HEPES buffer, Tris buffer, and PBS. The authors suggest that the ability to generate •OH during the decomposition of H2O2 is determined by the total surface area of ≡FeIIIOH particles, which significantly depends on the composition of the buffer in which these particles are formed.

Albumin-Functionalized Iron Oxide Nanoparticles for Theranostics: Engineering and Long-Term In Situ Imaging.

Magnetic nanosystems (MNSs) consisting of magnetic iron oxide nanoparticles (IONPs) coated by human serum albumin (HSA), commonly used as a component of hybrid nanosystems for theranostics, were engineered and characterized. The HSA coating was obtained by means of adsorption and free radical modification of the protein molecules on the surface of IONPs exhibiting peroxidase-like activity. The generation of hydroxyl radicals in the reaction of IONPs with hydrogen peroxide was proven by the spin trap technique. The methods of dynamic light scattering (DLS) and electron magnetic resonance (EMR) were applied to confirm the stability of the coatings formed on the surface of the IONPs. The synthesized MNSs (d ~35 nm by DLS) were intraarterially administered in tumors implanted to rats in the dose range from 20 to 60 µg per animal and studied in vivo as a contrasting agent for computed tomography. The long-term (within 14 days of the experiment) presence of the MNSs in the tumor vascular bed was detected without immediate or delayed adverse reactions and significant systemic toxic effects during the observation period. The peroxidase-like activity of MNSs was proven by the colorimetric test with o-phenylenediamine (OPD) as a substrate. The potential of the synthesized MNSs to be used for theranostics, particularly, in oncology, was discussed.

Kinetics and Mechanism of Synthesis of Carboxyl-Containing N-Vinyl-2-Pyrrolidone Telehelics for Pharmacological Use.

It was found that sulfanylethanoic and 3-sulfanylpropanoic acids are effective regulators of molecular weight with chain transfer constants of 0.441 and 0.317, respectively, and show an unexpected acceleration effect on the radical polymerization of N-vinyl-2-pyrrolidone, initiated by 2,2'-azobisisobutyronitrile. It was determined for the first time that the thiolate anions of mercapto acids form a high-temperature redox initiating system with 2,2'-azobisisobutyronitrile during the radical polymerization of N-vinyl-2-pyrrolidone in 1,4-dioxane. Considering the peculiarities of initiation, a kinetic model of the polymerization of N-vinyl-2-pyrrolidone is proposed, and it is shown that the theoretical orders of the reaction rate, with respect to the monomer, initiator, and chain transfer agent, are 1, 0.75, 0.25, and are close to their experimentally determined values. Carboxyl-containing techelics of N-vinyl-2-pyrrolidone were synthesized so that it can slow down the release of the anticancer drug, doxorubicin, from aqueous solutions, which can find its application in the pharmacological field.

Chemical Oxidative Polymerization of Methylene Blue: Reaction Mechanism and Aspects of Chain Structure.

The kinetic regularities of the initial stage of chemical oxidative polymerization of methylene blue under the action of ammonium peroxodisulfate in an aqueous medium have been established by the method of potentiometry. It was shown that the methylene blue polymerization mechanism includes the stages of chain initiation and growth. It was found that the rate of the initial stage of the reaction obeys the kinetic equation of the first order with the activation energy 49 kJ × mol-1. Based on the proposed mechanism of oxidative polymerization of methylene blue and the data of MALDI, EPR, and IR spectroscopy methods, the structure of the polymethylene blue chain is proposed. It has been shown that polymethylene blue has a metallic luster, and its electrical conductivity is probably the result of conjugation over extended chain sections and the formation of charge transfer complexes. It was found that polymethylene blue is resistant to heating up to a temperature of 440 K and then enters into exothermic transformations without significant weight loss. When the temperature rises above 480 K, polymethylene blue is subject to endothermic degradation and retains 75% of its mass up to 1000 K.

Redox-Active Aqueous Microgels for Energy Storage Applications.

The search for new environmental-friendly materials for energy storage is ongoing. In the presented paper, we propose polymer microgels as a new class of redox-active colloids (RACs). The microgel stable colloids are perspective low-viscosity fluids for advanced flow batteries with high volumetric energy density. In this research, we describe the procedure for the anchoring of 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (4-amino-TEMPO) redox-active sites to the polymeric chains of water-soluble microgels based on poly(N-isopropylacrylamide)-poly(acrylic acid) interpenetrating networks. Using cyclic voltammetry and EPR spectroscopy, we show that ca. 14% of 4-amino-TEMPO groups retain electroactive properties and demonstrate the reversible redox response. It allows achieving a stable capacity of 2.5 mAh/g, enabling the low-viscous catholyte with a capacity of more than 100 mAh/L.