Scavenging of reactive oxygen and nitrogen species with nanomaterials

Reactive oxygen and nitrogen species (RONS) are essential for normal physiological processes and play important roles in cell signaling, immunity, and tissue homeostasis. However, excess radical species are implicated in the development and augmented pathogenesis of various diseases. Several antioxidants may restore the chemical balance, but their use is limited by disappointing results of clinical trials. Nanoparticles are an attractive therapeutic alternative because they can change the biodistribution profile of antioxidants, and possess intrinsic ability to scavenge RONS. Herein, we review the types of RONS, how they are implicated in several diseases, and the types of nanoparticles with inherent antioxidant capability, their mechanisms of action, and their biological applications.     

Simultaneous determination of the recombination probability of nitrogen and oxygen atoms on quartz

The state of the problem of the heterogeneous recombination of nitrogen and oxygen atoms has been considered. A setup for measuring the probability of the heterogeneous recombination of atoms using resonance florescence spectroscopy has been described. The main feature of this method is the possibility of simultaneous registration of the concentration of N and O atoms in the air mixture in strictly controlled conditions. The temperature dependences of the probability of the recombination of nitrogen and oxygen atoms separately and in the combined recombination process on the quartz surface in the range of 300–600 K have been obtained. The proposed methodology also made it possible to start studying the mutual effect of the processes of the heterogeneous recombination of nitrogen and oxygen and to determine the fraction of the cross recombination.     

Development of optical nanoprobes for molecular imaging of reactive oxygen and nitrogen species

Reactive oxygen and nitrogen species (RONS) play important roles in cell signal transduction. However, overproduction of RONS is associated with a series of pathological processes and may disrupt cellular homeostasis, causing oxidative and nitrosative stress. Accurate methods to selectively and specifically monitor RONS in living systems are required to further elucidate the biological functions of these species. Optical imaging possesses high sensitivity, high spatiotemporal resolution, and real-time imaging capability. These qualities are advantageous for the detection of RONS in living systems. This review summarizes the development of optical nanoprobes with near-infrared (NIR) fluorescent, upconversion luminescent, chemiluminescent, or photoacoustic signals for molecular imaging of RONS in living systems. In this review, we discuss the design principles and advantages of RONS-responsive activatable nanoprobes, as well as applications of these optical imaging modalities in different disease models.     

An antibacterial mechanism of titanium alloy based on micro-area potential difference induced reactive oxygen species

Antimicrobial material is highly desired because of the increasing demand in biomedical application to prevent from the formation of biofilm. A common strategy for enhancing the antibacterial property of a metal material is to incorporate toxic metal such as Cu and Ag. However, the reported Cu²⁺ or Ag⁺ released concentration from antibacterial alloys was much less than the reported minimum inhibitory ion concentrations(MIC), revealing the existence of an unknown alternative...     

Efficient repairing effect of PEG based tri-block copolymer on mechanically damaged PC12 cells and isolated spinal cord

Membrane sealing effects of polymersomes made of tri-block copolymer, PEG-co-FA/SC-co-PEG, (PFSP) were studied on isolated spinal cord strips, PC12 cell lines and artificial bilayer following mechanical impact implemented by aneurism clip, sonication and electric shock, respectively. The homogeneity and size of PFSP, membrane permeability and cell viability were assessed by dynamic light scattering, LDH release and MTT assays. According to the results, the biocompatible, physico-chemical, size, surface charge and amphipathic nature of PFSP polymersome makes it an ideal macromolecule to rapidly reseal damaged membranes of cells in injured spinal cord as well as in culture medium. Compound action potentials recorded from intentionally damaged spinal cord strips incubated with PFSP showed restoration of neural excitability by 82.24 % and conduction velocity by 96.72 % after 5 min that monitored in real time. Thus, they triggered efficient instant and sustained sealing of membrane and reactivation of temporarily inactivated axons. Treatment of ultrasonically damaged PC12 cells by PFSP caused efficient cell membrane repair and led to their increased viability. The optimum effects of PFSP on stabilization and impermeabilizing of the lipid bilayer occurred at the same concentrations applied to the damaged cells and spinal cord fibers and was approved by restoration of membrane conductance and calcein release manifested by NanoDrop technique. The unique physico-chemical characteristics of novel polymersomes introduced here, make them capable to reorganize membrane lipid molecules, reseal the breaches and restore the hydrophobic insulation in spinal cord damaged cells. Thus, they might be considered in the clinical treatment of SCI at early stages.     

氢化物发生-原子荧光光谱法同时测定食盐中的砷和汞

建立一种氢化物发生-原子荧光光谱法同时测定食盐中砷和汞的方法.研究样品前处理对测定结果的影响,探索同时测定砷、汞的最佳实验条件.优化条件下,砷、汞质量浓度分别在0～10.0 μμg/L和0～2.0μg/L范围内,线性关系良好.方法检出限:As为0.0043 μg/L,Hg为0.003 2 μg/L;相对标准偏差:As为0.37％,Hg为0.61％;样品加标回收率:As为97.80％ ～ 102.40％,Hg为96.78％～ 100.80％.试验表明:该方法具有操作简便、快速、准确度高等优点,可用于食盐中砷汞的同时测定.     

Effect of chemically reactive species on properties of ZnO nanowires exposed to oxygen and hydrogen plasma

We present a systematic study on the effect of oxygen and hydrogen plasma-generated reactive species on the properties of ZnO nanowires. Upon exposure to oxygen plasma, the electrical conductivity of an individual ZnO nanowire decreased with substantial changes in the surface chemistry, indicating a decrease in the number of donor-like defects and an increase in the number of electron-trapping species. In contrast, an individual ZnO nanowire exposed to hydrogen plasma showed a drastic increase in conductivity up to two orders of magnitude due to the incorporated hydrogen acting as a shallow donor inside the ZnO nanowires without a sputtering process.     

Investigation on mechanism of growth arrest induced by iron oxide nanoparticles in PC12 cells

Iron oxide nanoparticles (Fe3O4 NPs) have recently received increasing interest in the biotechnology and life science. However, little is known about the nanoneurotoxicity of Fe3O4 NPs following exposure to neurons. This study was to elucidate the cytotoxicity and DNA damage of Fe3O4 NPs on PC12 cells line which derived from Rattus norvegicus pheochromocytoma. The cell viability was observed by MTS assay and cell cycle status was analyzed using flow cytometry. DNA damage related gene (P53) and its downstream targets (P21 and GADD45) were determined by semiquantitative RT-PCR. The results showed that exposure to Fe3O4 NPs at dosage levels between 25 and 200 microg/ml decreased cell viability respectively. The nanoparticles treatment caused cell cycle arrest in G2/M phase and the mRNA levels of P53 increased when PC12 cells were incubated with different concentrations Fe3O4 NPs. However, P21 and GADD45, the downstream targets of P53, were not affected. In summary, exposure to Fe3O4 NPs resulted in a dose-dependent cytotoxicity in cultured PC12 cells that was associated with increased P53 gene expression and much attention should be paid to the potential impact of Fe3O4 NPs on the central nervous system.     

Simultaneous determination of trace cadmium and arsenic in biological samples by hydride generation-double channel atomic fluorescence spectrometry

Hydride generation atomic fluorescence spectrometry (HG-AFS) has been used for determination of hydride-forming elements because of its high sensitivity, simplicity, and low costs, but most of such work has been concentrated on single element analysis, and reports dealing with multielement determination by HG-nondispersive (ND)AFS are rare. In this work, a sensitive HG-NDAFS method was developed for simultaneous determination of trace cadmium and arsenic in biological materials. The conditions for the generation of volatile cadmium and arsenic species from the reaction with KBH4 in aqueous solution were investigated using a double-channel AFS integrated with an intermittent flow reactor. Like thiourea and Co(II), ascorbic acid was found to significantly enhance the generation efficiency of volatile Cd and As species. The interferences of coexisting ions were evaluated. Under optimal conditions, the detection limits for Cd and As were determined to be 10 and 150 ng L(-1), respectively. The precision for 11 replicate determinations at the 1 microg L(-1) Cd level and the 10 microg L(-1) As level were 3.5 and 2.7% (RSD), respectively. The recoveries of spike analytes in the biological samples studied ranged from 94 to 109%. The proposed method was successfully applied to the simultaneous determination of Cd and As in a variety of biological samples.     

Simultaneous determination of thickness and refractive index based on time-of-flight measurements of terahertz pulse

We present a simple technique for simultaneous determination of thickness and refractive index of plane-parallel samples in the terahertz radiation domain. The technique uses time-of-flight measurements of the terahertz pulse. It has been employed on nine different polymers and semiconductor materials, which are transparent for terahertz frequencies. Our results of thickness measurement are in good agreement with micrometer reading. The accuracy in the determination of refractive index is on the order of two decimal points.     

Simvastatin downregulates the expression of hepcidin and erythropoietin in HepG2 cells

Statin therapy may improve responsiveness to erythropoietin‐stimulating agents in patients with end‐stage renal disease. Although statins increase hepatic iron uptake and storage capacity in cholestatic rats, the underlying mechanisms are unclear. Therefore, we examined the effects of a statin (simvastatin) on the expression of hepcidin, erythropoietin receptor (EPOR) and erythropoietin (EPO) in cultured HepG2 cells. HepG2 cells (6–6.5 × 10⁵ cells) were seeded in 6‐cm dishes and incubated overnight. The cells were then treated with 0, 0.5, 1, 3, 5, or 10 μM simvastatin, and the mRNA expression of hepcidin, EPOR, and EPO was determined. Data were collected from three independent experiments. The cDNA extracted from the cells was used as a template for real‐time polymerase chain reaction, and each sample was tested in duplicate. Significant differences (P < 0.05) among groups were determined using one‐way analysis of variance with Fisher's least significant difference post hoc test. Data were adjusted using Bonferroni's method. The relative mRNA expression of hepcidin in HepG2 cells treated with 0.5, 1, 3, 5, and 10 μM simvastatin, relative to the control group, was 0.7273, 0.3303, 0.2418, 0.4131, and 0.4064, respectively. The relative mRNA expression of EPOR was 0.5196, 0.2319, 0.2398, 0.4253, and 0.1245, respectively, while that of EPO was 0.9751, 0.4712, 0.4613, 0.4875, and 0.1654. There was a reverse dose‐dependent effect of simvastatin. These results suggest that statins increase erythropoiesis by targeting hepcidin and iron regulatory pathways, independent of erythropoietin.     

Temporal resolution in electrochemical imaging on single PC12 cells using amperometry and voltammetry at microelectrode arrays

Carbon-fiber-microelectrode arrays (MEAs) have been utilized to electrochemically image neurochemical secretion from individual pheochromocytoma (PC12) cells. Dopamine release events were electrochemically monitored from seven different locations on single PC12 cells using alternately constant-potential amperometry and fast-scan cyclic voltammetry (FSCV). Cyclic voltammetry, when compared to amperometry, can provide excellent chemical resolution; however, spatial and temporal resolution are both compromised. The spatial and temporal resolution of these two methods have been quantitatively compared and the differences explained using models of molecular diffusion at the nanogap between the electrode and the cell. A numerical simulation of the molecular flux reveals that the diffusion of dopamine molecules and electrochemical reactions both play important roles in the temporal resolution of electrochemical imaging. The simulation also reveals that the diffusion and electrode potential cause the differences in signal crosstalk between electrodes when comparing amperometry and FSCV.     

Chromatographic separation of nitrogen, argon, and oxygen in dissolved air for determination of triple oxygen isotopes by dual-inlet mass spectrometry

A chromatographic system was developed to separate oxygen from nitrogen, argon, carbon dioxide, and water vapor mixture for the determination of precise isotopic ratio measurements of oxygen in dissolved air. This system separates oxygen not only quantitatively but also rapidly as well; typical oxygen separation takes about 30 min. Fractionation of oxygen between liquid and gas phase was found to be similar to that of earlier reports.     

Microelectrode array biochip: tool for in vitro drug screening based on the detection of a drug effect on dopamine release from PC12 cells

Novel, yet simple detection techniques of drug effect, including the effect of a vesicular monoamine transporter inhibitor (reserpine), a dopamine precursor (L-dopa), and a dopamine transporter inhibitor (nomifensine), on dopamine release from dopaminergic PC12 cells were developed based on a microelectrode array (MEA) biochip. Upon multi-injections of KCl solution into the culture of PC12 cells attached on a MEA biochip, the K+-stimulated dopamine release was temporally and amperometrically recorded by biochip microelectrodes. Two parameters in the recorded amperometric spectra were defined in this study: the peak current of the first KCl injection (Max1), and the steady current after the fourth KCl injection (St4). Statistically significant effects of L-dopa and reserpine were demonstrated by comparing both Max1 and St4 of the second detections in drugs with those of the control without drug treatment. The values of both Max1 and St4 in the first detections were normalized as 1. In contrast, the statistically significant effect of nomifensine was detected by comparing the ratios of St4 to Max1 in the first detections in drug with those of the control. The reason for using different analytical methods for measurements between L-dopa/reserpine and nomifensine lies in the different mechanisms of action on PC12 cells among these drugs. The novel analytical methods developed use the same detection setup and parameters, and the data analysis for the effect of drugs becomes simple. The methods hence may provide a high-throughput in vitro drug screening approach for dopamine-related psychiatric disorders.     

Enhancement in dye-sensitized solar cells based on MgO-coated TiO(2) electrodes by reactive DC magnetron sputtering

A surface modification method was carried out by reactive DC magnetron sputtering to fabricate TiO(2) electrodes coated with insulating MgO for dye-sensitized solar cells. The MgO-coated TiO(2) electrode had been characterized by x-ray photoelectron spectroscopy (XPS), energy-dispersive x-ray spectroscopy (EDX), scanning electron microscopy (SEM), UV-vis spectrophotometer, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The study results revealed that the TiO(2) modification increases dye adsorption, decreases trap states and suppresses interfacial recombination. The effects of sputtering MgO for different times on the performance of DSSCs were investigated. It indicated that sputtering MgO for 3?min on TiO(2) increases all cell parameters, resulting in increasing efficiency from 6.45% to?7.57%.     

Interplay of reactive oxygen species (ROS) and tissue engineering: a review on clinical aspects of ROS-responsive biomaterials

Reactive oxygen species (ROS) refers to the reactive molecules and free radicals of oxygen generated as the by-products of aerobic respiration. Historically, ROS are known as stress markers that are linked to the response of immune cell against microbial invasion, but recent discoveries suggest their role as secondary messengers in signal transduction and cell cycle. Tissue engineering (TE) techniques have the capabilities to harness such properties of ROS for the effective regeneration of damaged tissues. TE employs stem cells and biomaterial matrix, to heal and regenerate injured tissue and organ. During regeneration, one of the constraints is the unavailability of oxygen as proper vasculature is absent at the injured site. This creates hypoxic conditions at the site of regeneration. Hence, effective response against the stresses like hypoxia spurs the regeneration process. Contrary, hyperoxic condition may increase the risk of ROS stress at the site. TE tries to overcome these limitations with the new class of biomaterials that can sense such stresses and respond accordingly. This review endeavors to explain the role of ROS in stem cell proliferation and differentiation, which is a key component in regeneration. This compilation also highlights the new class of biomaterials that can overcome the hypoxic conditions during tissue regeneration along with emphasis on the ROS-responsive biomaterials and their clinical applications. Incorporating these biomaterials in scaffolds development holds huge potential in tissue or organ regeneration and even in drug delivery.

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Simultaneous determination of mixtures of organic acids or bases based on the differences in the titration spectra

Based on the differences in titration spectra, mixtures of organic acids with similar pK_a were determined simultaneously. Principal component regression calibration was used for the evaluation of titration spectra. The effects of differences in pK_a and sampling interval of pH on accuracy were studied in detail. Combining precipitation and the acid–base reaction of organic acid, precipitation–acid–base titrimetry is proposed. The mixture of acids with almost the same pK_a can be determined simultaneously and accurately only if their pK_sp values are different. Synthetic mixtures of isomer of chlorobenzoic acid and homologue of phenol were determined simultaneously and acceptable results were obtained.