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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A novel nanostructure of cadmium oxide synthesized by mechanochemical method

Cauliflower-like cadmium oxide (CdO) nanostructure was synthesized by mechanochemical reaction followed calcination procedure. Cadmium acetate dihydrate and acetamide were used as reagents and the resulting precursor was calcinated at 450 °C for 2 h in air. The structures of the precursor and resultant product of the heating treatment were characterized using Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and elemental analysis, X-ray powder diffraction (XRD), energy-dispersive X-ray spectroscopy analysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction pattern (ED). SEM and TEM images revealed the cauliflower-like morphology of the sample. This structure includes the bundles of rods and tubes in nanoscale, which combine with each other and form the resulting morphology with the average diameter, 68 nm of the components. ED pattern indicated the single crystal nature of the formed bundles.     

Graphite oxide/poly(methyl methacrylate) nanocomposites prepared by a novel method utilizing macroazoinitiator

Graphite oxide (GO)/poly(methyl methacrylate) (PMMA) nanocomposites were prepared by a novel method utilizing macroazoinitiator (MAI). The MAI, which has a poly(ethylene oxide) (PEO) segment, was intercalated between the lamellae of GO to induce the inter-gallery polymerization of methyl methacrylate (MMA) and exfoliate the GO. The morphological, conductivity, thermal, mechanical and rheological properties of these nanocomposites were examined and compared with those of intercalated nanocomposites prepared by polymerization with the normal radical initiator, 2,2′-azobisisobutyronitrile. The improvement in conductivity by GO was more evident in exfoliated nanocomposites compared to that of intercalated nanocomposites. For example, a conductivity of 1.78 × 10⁻⁷ S/cm was attained in the exfoliated nanocomposite prepared with 2.5 parts GO per 100 parts MMA, which was about 50-fold higher than that of the intercalated nanocomposite. The thermal, mechanical and rheological properties also indicate that thin GO with a high aspect ratio is finely dispersed and effectively reinforced the PMMA matrix in both exfoliated and intercalated nanocomposites.     

Preparation and characterization of copper(II) oxide thin films grown by a novel spray pyrolysis method

A novel spray pyrolysis reactor was used to prepare thin films of CuO on silica substrates. The resulting films were characterized by x-ray diffraction, electron microscopy, optical and electrical measurements. The films were single phase, homogeneous, and uniform.     

反应射频磁控溅射制备高k氧化锆薄膜及介电性能的研究

在氧气和氩气的混合气体中,在O2/Ar混和气总流量固定的条件下,通过调节O2/Ar流量比,采用反应RF磁控溅射法制备了具有高介电常数的氧化锆薄膜。通过透射电子显微镜(TEM)和原子力显微镜(AFM)研究了O2/Ar流量比与薄膜微观组织和结构、表面平整度之间的关系,并测试分析了在不同O2/Ar流量比下溅射沉积的Al/ZrO2/SiO2/n型Si叠层结构的C V特性曲线。实验结果表明O2/Ar流量比与薄膜微观组织和结构有一定的关系。纯氧气氛下沉积的ZrO2薄膜基本上为纳米级的微晶,晶体结构为单斜结构(a=5.17、b=5.26、c=5.3、α=γ=90°,β=80.17°),在O2/Ar流量比为1∶4混合气氛下制备出了具有非晶结构的均质ZrO2薄膜;低的O2/Ar流量比下溅射得到的ZrO2薄膜样片,均方根粗糙度较低,表面平整度较好;在O2/Ar流量比为1∶4左右时,ZrO2薄膜的相对介电常数达到25。     

Hydrogen reduction of a RuO2 electrode prepared by DC reactive sputtering

RuO₂ thin films deposited by reactive DC sputtering were heat-treated in a 0.3%-H₂ atmosphere at 200°C in order to investigate the reduction property of RuO₂. The films were selectively reduced (starting from the interface) because of insufficient oxidation. When the as-deposited RuO₂/Si structure was hydrogen-reduced, the RuO₂ film was broken into fragments because of poor mechanical strength. On the other hand, the RuO₂ film heat-treated once in O₂ at 700°C cracked into a star shape as a result of vapor generation and volume shrinkage. The star-shape cracking was still observed even when the RuO₂ film was covered with a 90-nm-thick BST film. The mechanical strength and the adhesion of RuO₂ were improved to some extent by post-oxidation at high temperatures. However, a way to prevent the morphological destruction could not be found because of the thermodynamic equilibrium during the hydrogen reduction process.     

Preparation of indium-tin oxide (ITO) aciculae by a novel concentration-precipitation and post-calcination method

Indium-tin oxide (ITO) aciculae were prepared by adding tin into indium hydroxide aciculae, which were synthesized by a concentration-precipitation method, and subsequent calcining. X-ray powder diffraction (XRD) indicated that indium hydroxide aciculae were partially crystallized and ITO aciculae were a well-crystallized solid solution, and both of them had a cubic structure. Using scanning electron microscope (SEM), it was found that the cross-sectional diameters of most of ITO aciculae were in the range of 2 to 9 μm, and the aspect ratios of about 95% of aciculae were more than 6. Energy dispersion spectrometer (EDS) and phenylfluorone spectrophotometry analysis were used to measure Sn content of ITO aciculae, and it was revealed that the Sn content of the surface layer was higher than that of the bulk. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) showed that the intensive dehydration of In(OH)₃ took place in the temperature rage of 260–280 °C and the formation of ITO solid solution started at temperature higher than 280 °C. According to the results of XRD, TGA–DTA and N content analysis, indium-containing nitrates or nitrites maybe existed in indium hydroxide aciculae. The specific resistance of the pellet formed by pressing ITO aciculae at a pressure of 10 MPa was measured by a four-probe method at room temperature, and it was as low as 1.2×10⁻² Ω cm.     

Evaluation and characterization of nanostructure hydroxyapatite powder prepared by simple sol-gel method

Many attempts have been focused on preparing of synthetic hydroxyapatite (HA), which closely resembles bone apatite and exhibits excellent osteoconductivity. Low temperature formation and fusion of the apatite crystals have been the main contributions of the sol-gel process in comparison with conventional methods for HA powder synthesis. This paper describes the synthesis of nano-HA particles via a sol-gel method. Nanocrystalline powder of hydroxyapatite (HA) was prepared using Ca(NO₃)₂·4H₂O and P₂O₅ by a simple sol-gel approach. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for characterization and evaluation of the phase composition, morphology and particle size of products. The presence of amorphous and crystalline phases in the as-dried gel precursor was confirmed by the evaluating technique. Single phase of HA was also identified in the heat treated powder by XRD patterns. SEM and TEM evaluations showed that the obtained powder after heat treatment at 600 °C was agglomerated and composed of nanocrystalline (25-28 nm) HA particles. Increasing the sintering temperature and time could cause decomposition of HA into β-tricalcium phosphate and calcium oxide. The prepared nanocrystalline HA is able to improve the contact reaction and the stability at the artificial/natural bone interface for medical applications.     

(Fe,Co)-P thin films prepared with a reactive evaporation method

Magnetic properties of (Fe,Co)/sub 2/P thin films prepared with the thermal-activated reactive evaporation method were investigated for recording media application. Above 300 degrees C, metals (Fe,Co) and phosphorus react to form M/sub 2/P. The coercive forces of these films had a maximum value of 1.3 kOe at 10% Co concentration, and the saturation magnetization increased with the increase in Co concentration. Annealing at 500 degrees C for 30 min increased the coercive force of the films up to two times. The reproduced output from the isolated magnetization transitions of a (Fe,Co)-P-film rigid disk with a ring head showed waveforms of typical longitudinal recording. A recording density of 62 kfrpi at D/sub 50/ was attained with a disk medium of about an 800-AA-thick layer.<>     

Properties and catalytic activity of NOx reduction of alumina-titania catalysts prepared by sol-gel method

The alumina-titania catalysts were prepared from various alumina and titania sources by sol-gel method, which were metal alkoxide and metal alkoxide modified with organic groups. Specific surface area, pore size distribution, solid acidity and catalytic activity of NO reduction for the alumina-titania catalysts depended on the alumina and titania sources. The alumina-titania catalyst prepared from metal alkoxide for alumina source and metal alkoxide modified with organic groups for titania source exhibited higher activity of NO reduction than the other alumina-titania catalysts. Catalytic activity of NO reduction for the alumina-titania catalysts depended on specific surface area and solid acidity. It was suggested that solid acidity of the alumina-titania catalysts depended on the coordination structure of Al atoms and the homogeneity of alumina and titania components.     

Effects of oxygen percentage on the growth of copper oxide thin films by reactive radio frequency sputtering

Copper oxide thin films were deposited onto glass substrates by reactive radio frequency magnetron sputtering at various oxygen percentage flow rates R(O₂). X-ray diffraction analysis revealed that nanocrystallite copper oxide thin films with cubic, tetragonal, and monoclinic structure were formed at R(O₂) values of 10%, 20%, and ≥30%, respectively. Energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy were used to verify the copper oxides phases. With increased R(O₂), the root mean square surface roughness of the deposited films decreased from 4.82 nm to 1.78 nm. Moreover, both the band gap type and value changed with increased R(O₂). For R(O₂) at 20%, single phase tetragonal Cu₄O₃ thin film with a direct band gap of 2.20 eV was formed. For R(O₂) ≥ 30%, single phase monoclinic CuO thin films with an indirect band gap of 1.20 eV–1.25 eV were formed. In addition, conductive copper oxide thin films tended to form for R(O₂) < 30%, whereas insulator oxide thin films tended to form for R(O₂) ≥ 30%. Through this study, the crystallization behavior, the band gap, and the resistivity properties of the deposited copper oxide thin films as a function of the R(O₂) were obtained.     

Modulation of the activity of the NADPH oxidase system by reactive oxygen species: influence of catalase

The nicotinamide adenine dinucleotide phosphate oxidase complex (Nox) is a major source of non-mitochondrial reactive oxygen species in cells. Nox contains both membrane (Cytb(558)) and cytosolic (p40(phox), p47(phox), p67(phox) and Rac) components. Nox has been submitted to a combination of oxygen free radicals produced by irradiation and to hydrogen peroxide. Irradiation of a single component with high doses led to partial inactivation; however, the irradiation of the whole system during its assembly phase with lower doses (2-10 Gy) led either to activation (2.7 Gy) or to strong inactivation if irradiation took place during the first minute of the assembly. Incubation of the membrane fractions or of p67(phox) with H(2)O(2) led to fast inactivation. Catalase protected weakly p67(phox) from H(2)O(2). Conversely, incubation of the membrane fractions with catalase led to over-activation of the system.     

Biomechanisms of nanoparticles (toxicants, antioxidants and therapeutics): electron transfer and reactive oxygen species

In recent years, nanoparticles have received increasing attention in research and technology, including a variety of practical applications. The bioactivity appears to be related to the small particle size, in addition to inherent chemical activity as electron transfer (ET) agents, generators of reactive oxygen species (ROS) with subsequent oxidative stress (OS) and as antioxidants (AOs). The mechanism of toxicity, therapeutic action and AO property is addressed based on the ET-ROS-OS approach. There are several main classes of ET functionalities, namely, quinones (or phenolic precursors), metal compounds, aromatic nitro compounds (or reduction products) and imine or iminium species. Most of the nanospecies fall within the metal category. Cell signaling is also discussed. This review is apparently the first to address the various bioactivities based on the ET-ROS-OS-AO framework.     

Facile construction of manganese oxide doped carbon nanotube catalysts with high activity for oxygen reduction reaction and investigations into the origin of their activity enhancement

MnOx-doped carbon nanotube (MnOx-CNTs) catalysts for the oxygen reduction reaction (ORR) were fabricated using a simple electrochemical deposition method. MnOx-CNTs (0.85 wt % MnOx) could exhibit an improved electrocatalytic activity, long-term stability and excellent resistance to crossover-effect compared to Pt/C catalysts. High-resolution transmission electron microscopy (HRTEM) and X-ray diffraction analysis confirm that the MnOx in the MnOx-CNTs exists in an amorphous state. Moreover, compared to the catalytic performances of MnOx on other substrates, the MnOx-CNTs exhibit a high ORR activity. X-ray photoelectron spectroscopy results suggest that the electron transfer, from the CNTs to the Mn ions occurs and the high positive charge is generated on the MnOx-CNT surface. This is believed to be origin of the catalytic activity observed in the ORR using MnOx-CNTs.     

Low temperature dielectric studies of zinc oxide (ZnO) nanoparticles prepared by precipitation method

Using zinc nitrate as a precursor and NaOH starch as a stabilizing agent, hexagonal zinc oxide (ZnO) nanoparticles has been synthesized by precipitation method. The transmission electron microscopy (TEM) images show particles of nearly uniform spherical size of around 40 nm. The infrared spectroscopy (FT-IR) measurement reveals the peak at 500 cm^?1, corresponding to the Zn–O bond. Dielectric studies of ZnO nanoparticles show frequency dependence dielectric anomaly at low temperature (85–300 K). Results reveal that the capacitance and loss tangent decrease with the frequency while these parameters improve with the increasing of temperature. The increase of a.c. conductivity with the temperature indicates that the mobility of charge carriers is responsible for hopping and electronic polarization in ZnO nanoparticles.     

Microstructure trends in metal(aluminum,copper, indium,lead, tin)-metal oxide thin films prepared by reactive ion beam sputter deposition

Transmission electron microscopy has been used to study the microstructural trends of thin film composites prepared by sputtering of a metal (aluminum, copper, indium, lead or tin) target with argon ions in the presence of a reactive gas (oxygen). Results of these studies reveal that there is a general progression in the metal component microstructure which correlates with an increasing metal oxide component in the films and can be classified as belonging to an agglomerated-columnar-granular-amorphous sequence. These structural trends and the concomitant effect on film properties, such as resistivity, adhesion and mechanical stability, are a direct consequence of the metal-metal oxide interaction and the inhibiting effect which the native metal oxides have on metal atom diffusion during film formation.     

Supported and unsupported platinum catalysts prepared by a one-step dry deposition method and their oxygen reduction reactivity in acidic media

The present study examines the physical and electrochemical properties of platinum particles generated by a combustion method for use in oxygen reduction on the cathode side of a proton exchange fuel cell (PEMFC). This method employs a one-step, open-atmosphere, and dry deposition technique called reactive spray deposition technology (RSDT). The objective of this study is to characterize the intrinsic activity of the platinum produced for incorporation into low-loading cathode electrodes in high performing membrane electrode assemblies (MEA). The process allows for independent real-time control of the carbon, platinum, and ionomer ratios in the final electrode. In this research work we examine the oxygen reduction reaction via a rotating disk three electrode set-up to understand the intrinsic activity of the as-sprayed platinum as well as platinum condensed onto a carbon support. The mass and specific activities were measured in a 0.1 M perchloric acid electrolyte under different deposition conditions and loading was verified by atomic emission spectroscopy inductively coupled plasma (AES-ICP). Microscopy results indicate that the platinum particle sizes are 5 nm (σ = 2.8 nm) in diameter while TEM and XRD show that the platinum generated by the process is pure and crystalline without bulk oxides or precursor material present. The initial rotating disk electrode result shows that the RSDT technique is capable of producing catalysts with an oxygen reduction mass activity at 0.9 V of 200 mA/mg_Pt rotating at 1600 rpm and 30 °C. The electrochemically active surface area approaches 120 m²/g for the platinum, carbon, and ionomer samples and the unsupported sample with only platinum has an active area of 92 m²/g. The rather larger surface area of the unsupported sample exists when the platinum is deposited as a highly porous nanostructured layer that allows for high penetration of reactant.     

Synthesis of copper and copper(I) oxide nanoparticles by thermal decomposition of a new precursor

The present investigation reports, the novel synthesis of nanoparticles Cu and Cu₂O using thermal decomposition and its physicochemical characterization. The nanoparticles copper powder have been prepared using [Bis(salicylidiminato)copper(II)], [Cu(sal)₂], as precursor. Cu nanoparticles are initially formed and subsequently oxidized to form Cu₂O. Transmission electron microscopy (TEM) analysis demonstrated nanoparticles Cu₂O with an average diameter of about 10 nm. As-prepared copper nano-particles were characterized by X-ray diffraction measurements (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), and Fourier transform infra-red spectroscopy (FTIR). XRD analysis revealed broad pattern for fcc crystal structure of copper metal and cubic cuprite structure for Cu₂O. Optical absorption measured by UV–visible spectroscopy was used to monitor oxidation course of Cu → Cu₂O and to determine the band-gap energy about 2.4 eV for Cu₂O nanoshells.     

Detection of reactive oxygen species (ROS) generated by TiO2(R), TiO2(R/A) and TiO2(A) under ultrasonic and solar light irradiation and application in degradation of organic dyes

In the present work, the rutile, anatase and mixed (rutile and anatase) crystal phase TiO₂ powders were irradiated by ultrasound and solar light, respectively, and the generation of reactive oxygen species (ROS) were detected through the oxidation reaction from 1,5-diphenyl carbazide (DPCI) to 1,5-diphenyl carbazone (DPCO). The DPCO can be extracted by the mixed solvent of benzene and carbon tetrachloride and the extract liquors display an obvious absorption peak around 563 nm. In addition, the influences of (ultrasonic or solar light) irradiation time, TiO₂ addition amount and DPCI concentration on the quantities of generated ROS were also reviewed. The kinds of generated ROS were determined by using several radical scavengers. At last, the researches on the sonocatalytic and photocatalytic degradation of several organic dyes were also performed. It is wished that this paper might offer some important subjects for broadening the applications of sonocatalytic and photocatalytic technologies.     

Large-scale synthesis of a novel tri(8-hydroxyquioline) aluminum nanostructure

A novel tri(8-hydroxyquioline) aluminum (AlQ3) nanostructure was prepared on large scale at low cost by low-temperature physical vapor deposition (PVD). The morphologies, the chemical bondings, and photoluminescence of the AlQ3 nanostructure were investigated by environmental scanning electronic microscopy (ESEM), Fourier transform infrared spectrum (FT-IR), and photoluminescence (PL) spectra, respectively. The AlQ3 nanostructure was composed of micro-sphere with nanowire-cluster growing on the surface. The diameter of micro-sphere and nanowire were about 5 microm and 80 nm, respectively. FT-IR results indicated that the AlQ3 molecule had a strong thermal stability under research conditions. The growth mechanism of the novel nanostructure was discussed. The novel organic nanostructure would be believed to attractive building field-emission devices and other optical devices.