TiO2/ZnO 复合材料的制备及其在不同条件下的抗菌性能研究?

采用水热合成法制备出 TiO2/ZnO 复合材料,通过 XRD、SEM和 EDX 对所制备粉体颗粒的物相组成以及微观形貌进行了表征,并通过抑菌环试验和菌液接触试验测试了TiO2/ZnO 复合材料的抗菌性能.结果表明,制备出的 TiO2/ZnO 复合材料的晶相组成为锐钛矿相、金红石相和六方纤锌矿相,其表面存在细小的片状结构.TiO2/ZnO 复合材料的压片在可见光照射条件下能够对大肠杆菌产生直径22 mm 的抑菌环,菌液接触试验2 h 后除菌率即达96．4％,4 h后除菌率高达99．9％以上.可见光照射有利于提高TiO2/ZnO 复合材料的初期除菌率.在4~30℃范围内,较高温度对 TiO2/ZnO 复合材料抗菌性能有促进作用.     

Structural, optical, photo catalytic and antibacterial activity of ZnO and Co doped ZnO nanoparticles

A systematic investigation on the structural, optical, photo catalytic and antimicrobial properties of pure and cobalt doped ZnO nanoparticles synthesized by Co-precipitation method is presented. X-ray diffraction analysis of these samples showed the formation of phase pure nanoparticles with wurtzite ZnO structure. Optical studies showed a blue shift in the absorbance spectrum with increasing the doping concentration. The Methylene Blue (MB) decomposition rate of the synthesized pure ZnO and cobalt doped ZnO nanoparticles were studied under the UV region. In the UV region, synthesized pure ZnO and cobalt doped ZnO decomposed Methylene Blue (MB). However, the MB decomposition rate obtained using pure ZnO was much higher than that by doped ZnO. The antibacterial property test was carried out via disk diffusion method, and the result indicated antibacterial activity of the prepared samples.     

In vitro degradation behavior of silica nanoparticles under physiological conditions

Understanding the degradability of silica nanoparticles is significant for the rational design of desired nanomaterials for various biomedical applications. However, the effect of the intrinsic properties of silica nanoparticles, such as particle shape, surface chemistry, and porosity, on kinetic degradation process under different extrinsic conditions has still received little attention. Herein, mesoporous silica nanoparticles (MSNs) with different aspect ratios (ARs, 1, 2, and 4), the corresponding PEG-functionalized MSNs, and amorphous St?ber spherical silica nanoparticles were specially designed and their degradation was evaluated in in vitro simulated physiological media. The results show that shape, surface properties and porosity of nanoparticles, as well as the component of simulated physiological media, play important roles in tuning the degradation kinetics and behaviors. Sphere-shaped MSNs have a faster degradation rate than rod-shaped counterparts. Naked MSNs are eroded from particle external surface, while PEGylated MSNs from interior of particles. And spherical MSNs display more extensive degradation than amorphous silica nanoparticles. The presence of fetal bovine serum (FBS) in Dulbecco's Modified Eagle's Medium (DMEM) can accelerate the degradation process. These results can provide useful guidelines for the rational design of silica nanoparticles for biomedical applications.     

层流状态下纳米流体的对流传热特性

通过数值模拟的方法研究了层流状态下雷诺数、体积分数、颗粒和基液种类以及颗粒粒径对纳米流体对流传热特性的影响。研究结果表明,纳米流体的对流传热系数明显高于基液,并且与基液和颗粒的性质、颗粒的体积分数及颗粒粒径密切相关。纳米流体的对流传热系数随着颗粒和基液热导率的增加、颗粒体积分数的增加以及颗粒粒径的减小而增大。研究发现,对于一定体积分数的Cu-水纳米流体,在层流状态下对流传热系数的提高程度基本保持一致,与雷诺数大小无关。     

壳聚糖/羟基磷灰石-庆大霉素缓释材料的抗菌性能研究及AFM观察

制备壳聚糖/羟基磷灰石-庆大霉素(CS/HA-G)缓释材料,评价其抗茵性能在骨髓炎的治疗中的应用前景;并从微观角度初步探讨药物对大肠杆菌的作用机制.对CS/HA-G缓释材料进行体外缓释行为研究及抗茵实验;并以原子力显微镜(AFM)观察大肠杆茵在药物作用前后表面形态结构的变化.CS/HA-G对大肠杆茵的抑茵效果显著,维持有效释药时间长达30d以上.AFM观察显示药物作用于大肠杆菌后菌体高度和表面平均粗糙度(Ra)均下降,有内容物渗漏.CS/HA是一种理想的庆大霉素载体材料.CS/HA-G的缓释作用和缓释规律显示出该材料在大肠杆菌引发的骨髓炎的防治中具有极大的临床应用潜能.     

Investigation on passivity of titanium under steady-state conditions in acidic solutions

The passivity of titanium was studied using potentiostatic polarization combined with Mott–Schottky analysis in acidic solutions. The oxide layer was characterized as an n-type semiconducting, oxygen deficient oxide (TiO_{1.993–1.996}) with a donor density in the range of 10¹⁹–10²⁰ cm⁻³ depending on electrode potential and electrolyte pH. The calculated thickness for the inner oxide layer was in the range of 1–4 nm, increasing linearly with applied potential and exponentially with electrolyte pH. The potential- and pH-dependence of the inner oxide thickness was interpreted by a modified point defect model for the migration-controlled oxide growth, in which the rate-determining step in the passive film growth processes was assumed to be the donor lattice migration.     

In vitro adhesion of staphylococci to diamond-like carbon polymer hybrids under dynamic flow conditions

This study compares the ability of selected materials to inhibit adhesion of two bacterial strains commonly implicated in implant-related infections. These two strains are Staphylococcus aureus (S-15981) and Staphylococcus epidermidis (ATCC 35984). In experiments we tested six different materials, three conventional implant metals: titanium, tantalum and chromium, and three diamond-like carbon (DLC) coatings: DLC, DLC–polydimethylsiloxane hybrid (DLC–PDMS-h) and DLC–polytetrafluoroethylene hybrid (DLC–PTFE-h) coatings. DLC coating represents extremely hard material whereas DLC hybrids represent novel nanocomposite coatings. The two DLC polymer hybrid films were chosen for testing due to their hardness, corrosion resistance and extremely good non-stick (hydrophobic and oleophobic) properties. Bacterial adhesion assay tests were performed under dynamic flow conditions by using parallel plate flow chambers (PPFC). The results show that adhesion of S. aureus to DLC–PTFE-h and to tantalum was significantly (P < 0.05) lower than to DLC–PDMS-h (0.671 ± 0.001 × 10⁷/cm² and 0.751 ± 0.002 × 10⁷/cm² vs. 1.055 ± 0.002 × 10⁷/cm², respectively). No significant differences were detected between other tested materials. Hence DLC–PTFE-h coating showed as low susceptibility to S. aureus adhesion as all the tested conventional implant metals. The adherence of S. epidermidis to biomaterials was not significantly (P < 0.05) different between the materials tested. This suggests that DLC–PTFE-h films could be used as a biomaterial coating without increasing the risk of implant-related infections.     

Synthesis,characterization and evaluation of bioactivity and antibacterial activity of quinary glass system (SiO2–CaO–P2O5–MgO–ZnO): In vitro study

Bioactive glasses in the systems SiO₂–CaO–P₂O₅–MgO (BGZn0) and SiO₂–CaO–P₂O₅–MgO–ZnO (BGZn5), were prepared by sol–gel method and then characterized. Surface reactivity was studied in simulated body fluid (SBF) to determine the effect of zinc (Zn) addition as a trace element. The effect of Zn addition to the glass matrix on the formation of apatite layer on the glass surface was investigated through X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT–IR) and scanning electron microscopy (SEM). Also, inductively coupled plasma–optical emission spectroscopy (ICP–sOES) was used to determine the concentrations of released ions in SBF solution after different time intervals in SBF solution. The antibacterial activity of Zn containing glass against Pseudomonas aeruginosa was measured by the halo zone test. The presence of Zn in glass composition improved chemical durability, slowed down the formation rate of Ca–P layer and decreased the size of crystalline apatite particles. Zn containing glass exhibited an excellent antibacterial activity against P. aeruginosa which could demonstrate its ability to treat bone infection.     

Investigation of the state of metal surfaces under boundary-lubrication conditions in the presence of additives

The concepts of secondary structures and boundary friction were substantial in the framework of the theory of the nature of the phenomena taking place during friction. The results of an investigation into changes in the state of metal surfaces under the influence of iron and copper rhodanide additions in lubricating oils are described as an example. Schematic models were proposed for the structure of metal surface layers produced under normal frictional conditions and as a result of seizing of the I-st and II-nd kind.Translated from Fiziko-Khimicheskaya Mekhanika Materialov, Vol. 5, No. 5, pp. 559–564, Septmeber–October, 1969.     

Anaerobic biodegradation of fluoranthene under methanogenic conditions in presence of surface-active compounds

Bacillus cereus isolated from municipal wastewater treatment plant was used as a model strain to assess the efficiency of two anionic surfactants, a chemical surfactant and a biosurfactant during fluoranthene biodegradation under anaerobic methanogenic conditions. The surfactants selected for the study were linear alkyl benzene sulphonates (LAS) and rhamnolipid-biosurfactant complex from Pseudomonas sp. PS-17. Biodegradation of fluoranthene was monitored by GC/MS for a period up to 12th day. No change in the fluoranthene concentration was registered after 7th day. The presence of LAS enhanced the cell growth as well as the fluoranthene biodegradation. The rhamnolipid-biosurfactant at both used concentrations inhibited the cell growth and had no effect on the biodegradation rate. It was shown that LAS did not affect the microbial cell permeability and its positive effect on fluoranthene biodegradation was most likely as a result of the increased fluoranthene solubility. The results indicate that LAS can be considered as a promising agent for facilitation of the process of anaerobic polycyclic aromatic hydrocarbons (PAH) biodegradation under methanogenic conditions.     

In vitro assessment of acyclovir permeation across cell monolayers in the presence of absorption enhancers

The aim of the investigation was to establish transepithelial permeation of acyclovir across Caco-2 and Madin-Darby canine kidney (MDCK) cell monolayers and attempt to improve its permeation by employing absorption enhancers (dimethyl β cyclodextrin, chitosan hydrochloride and sodium lauryl sulfate) and combinations thereof. Caco-2 and MDCK cell monolayers have been widely employed in studying drug transport, mechanisms of drug transport, and screening of absorption enhancers and excipients. Transepithelial electrical resistance and permeation of ^99mTc-mannitol were employed as control parameters to assess the tight junction and paracellular integrity. Permeation of acyclovir in the presence of absorption enhancers was found to be significantly higher compared with drug permeation in their absence when assessed as apparent permeability coefficients (P_app). Synergistic improvements in P_app values of acyclovir were obtained in case-selected combinations of absorption enhancers; dimethyl β cyclodextrin-chitosan hydrochloride, chitosan hydrochloride-sodium lauryl sulfate, and dimethyl β cyclodextrin-sodium lauryl sulfate, were used. Recovery and viability assessment studies of both cell monolayers suggested reestablishment of paracellular integrity and no damage to cell membranes. Significantly improved permeation of acyclovir in the presence of selected combinations of absorption enhancers may be used as a viable approach in overcoming the problem of limited oral bioavailability of acyclovir.     

Boiling of a superheated liquid in the presence of a metallic surface under isothermal conditions

Measurements are made of the temperature dependences of the mean times before the boiling, at atmospheric pressure, of superheated n-pentane and n-hexane in a glass capillary tube, and with the introduction of a metal wire into the tube.     

Electrodeposition of ZnO nanorods in the presence of metal ions

We report on structural and optical changes induced by impurity incorporation in ZnO nanorods grown via electrodeposition. We find the lattice parameters of the hexagonal ZnO rods to be larger than in defect-free single-crystalline ZnO. SIMS measurements indicate impurity incorporation and doping in the bulk of the nanorods. The impurity content correlates with changes in the electroluminescence spectra. The maximum of the defect luminescence band around 600 nm shifts towards longer wavelengths with metal incorporation. Aluminum incorporation leads to a narrow luminescence band close by the bandgap of ZnO around 390 nm.     

Synthesis, structural and optical characterization of ZnO crystals grown in the presence of silver

Zinc oxide microcrystals grown at atmospheric pressure by the laser assisted flow deposition method were characterized by morphological, structural and optical techniques. A set of samples with 0, 0.8, 2.0, 3.0 and 5.0 mol% nominal AgNO₃ content were studied in order to analyse the influence of silver amount on the near band edge recombination. A detailed study of the samples' photoluminescence evidence that at room temperature the free exciton recombination occurs at ~ 3.334 eV for crystals grown in the presence of silver instead of the broad peak observed at ~ 3.28 eV for the undoped ones.     

Hydrothermal synthesis of ZnO nanorods in the presence of a surfactant

Controlling the dimensions, positioning, and shapes of semiconductor nanowires, nanorods, and nanobelts lies in the synthesis and understanding of their growth mechanism. Controlled growth and synthesis is required in the fabrication of nanodevices and nanosensors. Among methods utilized for one-dimensional nanostructure synthesis, the hydrothermal process--a simple and cost-effective technique involving a low process temperature--has emerged as a powerful tool for the fabrication of anisotropic nanomaterials. Under hydrothermal conditions, many starting materials can undergo quite unexpected reactions, which are often accompanied by the formation of nanoscopic morphologies that are not accessible by classical routes. Synthesized ZnO nanostructures from aqueous solutions are usually poor in terms of morphology and size control. To improve the growth conditions and the controllability of the process, the use of surfactants or organic solvents has been attempted. In the present work, ZnO nanorods were grown on templates with a pre-sputtered ZnO seed layer over oxidized Si (100) substrates, and polyvinyl pyrrolidone (PVP) was used as a surfactant. By varying the PVP concentration in the growth solution, we can control the diameter and density of ZnO nanorods. The optical property of ZnO nanorods is highly improved by PVP addition.     

Deposition of ZnO on the surface of Al metal particles by esterification reaction under solvothermal conditions

ZnO nanoparticles were synthesized by esterification reaction between zinc acetate and absolute ethanol under solvothermal conditions. The influences of reaction parameters and different surfactants on the size and morphology of synthesized ZnO nanoparticles were studied. As the application of this reaction, ZnO particles were deposited on the surface of Al particles using the same solvothermal process. The deposition reaction time and amount of reactants to the distribution density of deposited ZnO nanoparticles were studied. X-ray diffraction and transmission electron microscopy were used to characterize the synthesized ZnO nanoparticles and ZnO/Al composite particles.     

In vitro antifungal activity and toxicity of itraconazole in DMSA-PLGA nanoparticles

Itraconazole (ITZ) is a drug used to treat various fungal infections and may cause side effects. The aim of this study was to develop and evaluate the in vitro activity of DMSA-PLGA nanoparticles loaded with ITZ against Paracoccidioides brasiliensis, as well as their cytotoxicity. Nanoparticles were prepared using the emulsification-evaporation technique and characterized by their encapsulation efficiency, morphology (TEM), size (Nanosight) and charge (zeta potential). Antifungal efficacy in P. brasiliensis was determined by minimal inhibition concentration (MIC), and cytotoxicity using MTT assay. ITZ was effectively incorporated in the PLGA-DMSA nanoparticles with a loading efficiency of 72.8 +/- 3.50%. The shape was round with a solid polymeric structure, and a size distribution of 174 +/- 86 nm (Average +/- SD). The particles were negatively charged. ITZ-NANO presented antifungal inhibition (MIC = 6.25 ug/mL) against P. brasiliensis and showed lower in vitro cytotoxicity than free drug (ITZ).     

Simultaneous crystallization of calcium phosphate and calcium oxalate in the presence of ascorbic acid under physiological conditions

Ascorbic acid (AA—Vitamin C) plays a vital role in human body to preserve optimal health. However, high intake may cause the formation of pathological calcium oxalate stones. Calcium oxalate and calcium phosphates are the major crystalline constituents of the urinary calculi and commonly found together. The effect of AA on the crystallization of calcium phosphate was studied in gel matrix under physiological conditions. Calcium phosphates such as hydroxyapatite (HAp), brushite (DCPD) and calcium oxalate dihydrate (COD—Weddellite) were found to crystallize simultaneously in the gel matrix. The formation of HAp is accelerated by AA. A possible reaction scheme for the formation of COD by the metal induced conversion of AA is proposed.     

Undamped self-oscillations in a compensated semiconductor under conditions of impurity breakdown in the presence of a magnetic field

Conditions for the generation of undamped self-oscillations in a compensated semiconductor in the presence of a magnetic field are studied. Pis’ma Zh. Tekh. Fiz. 23, 62–66 (August 26, 1997)