Influence of stabilizers on the antimicrobial properties of silver nanoparticles introduced into natural water

Physical, chemical and biochemical properties of silver nanoparticles(AgNPs) depend to a great extent on their size, shape, size distribution, and stabilizers located on their surface. This study focused on two typical stabilizers, namely citrates(cit), low molecular ions protecting nanoparticles by electrostatic repulsion, and polyvinylpyrrolidone(PVP), a hydrophilic, neutral, high molecular polymer protecting nanoparticles by steric stabilization. Natural bacterioplankton was collected from a eutrophic, downtown lake and exposed to five concentrations(0.1–5 mg/L) of AgNPs-PVP and AgNPs-cit. Responses were monitored after 1, 3, 5 and 7 days of exposure, by evaluating the survival rate of bacteria, their respiratory activity, and the general activity of extracellular esterases. A significantly better(greater) survival rate of bacterioplankton was observed in water with an addition of AgNPs-cit. The inhibition of extracellular esterases was observed only in samples containing AgNPs-PVP. The inhibitory effect increased proportionally to the concentration of AgNPs-PVP applied. Within the studied concentration range, there was no statistically significant inhibition of bacterioplankton respiratory activity by AgNPs-PVP and AgNPs-cit.     

Intracellular biosynthesis of Au and Ag nanoparticles using ethanolic extract of Brassica oleracea L. and studies on their physicochemical and biological properties

In this present study, we reported broccoli (Brassica oleracea L.) as a potential candidate for the synthesis of gold and silver nanoparticles (NPs) in green chemistry method. The synthesized metal nanoparticles are evaluated their antimicrobial efficacy against different human pathogenic organisms. The physico-chemical properties of gold nanoparticles were analyzed using different analytical techniques such as a UV-Vis spectrophotometer, Field Emission Scanning Electron Microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and a Fourier Transform Infrared spectrophotometer. In addition, gold and silver NP antimicrobial efficacy was checked by disc diffusion assay. UV-Vis color intensity of the nanoparticles was shown at 540 and 450 nm for gold and silver nanoparticles respectively. Higher magnification of the Field Emission Scanning Electron Microscopy image shows the variable morphology of the gold nanoparticles such as spherical, rod and triangular shapes and silver nanoparticles were seen in spherical shapes. The average spherical size of the particles was observed in 24- 38 nm for gold and 30-45 nm for silver NPs. X-ray diffraction pattern confirmed the presence of gold nanoparticles and silver nanoparticles which were crystalline in nature. Additionally, the functionalmetabolites were identified by the Fourier TransformInfrared spectroscopy. IR spectra revealed phenols, alcohols, aldehydes (sugar moieties), vitamins and proteins are present in the broccoli extract which are accountable to synthesize the nanoparticles. The synthesized gold and silver NPs inhibited the growth of the tested bacterial and fungal pathogens at the concentration of 50 μg/mL respectively. In addition, broccoli mediated gold and silver nanoparticles have shown potent antimicrobial activity against human pathogens. © 2015 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences.     

Comparison studies of adsorption properties of MgO nanoparticles and ZnO–MgO nanocomposites for linezolid antibiotic removal from aqueous solution using response surface methodology

In this investigation, the adsorption measure of linezolid antibiotic onto MgO nanoparticles and ZnO–MgO nanocomposites were performed. The adsorbents were characterized by different techniques such as XRD, SEM, TEM and BET. The parameters influence such as the pH, adsorbent dosage and temperature was tested and evaluated by Box–Behnken Design combined with response surface methodology. Performing adsorption tests at optimal conditions set as 0.5 g L⁻¹ of adsorbent, pH 10 and 308 K make admit to obtain high adsorption turnover (123.45 and 140.28 mg g⁻¹ for MgO nanoparticles and ZnO–MgO nanocomposites, respectively). A good compromise between predicted and experimental data in this research was observed. The experimental equilibrium data fitting to Langmuir, Freundlich, Tempkin and Dubinin–Radushkevich models indicate that the Langmuir model is a best model for evaluation of adsorption behavior. Kinetic evaluation of experimental data indicated that the adsorption operations followed well pseudo-second-order models. The adsorption capacity of ZnO–MgO nanocomposites is higher than MgO nanoparticles that because of the ZnO–MgO nanocomposites have high specific surface area.     

Cadmium sulfide nanoparticle induces oxidative stress and pro-inflammatory effects in human lung adenocarcinoma epithelial cells

Cadmium sulfide nanoparticles (CdSNP) are increasingly used in biological applications. This study was undertaken to understand the mechanisms underlying adverse effects of CdSNP using human lung adenocarcinoma epithelial (A549) cells. Cellular toxicity was evaluated by using 3-(4,5-dimethylthiazol-2-yl)-2,5 diphenyltetrazolium bromide and neutral red assays. Results showed that CdSNP reduced mitochondrial function and induced lysosomal activity in concentration and time-dependent manner. CdSNP produced oxidative stress as evidenced by reduction of glutathione (GSH) levels and increase in reactive oxygen species and lipid peroxidation levels. Induction of caspase-3 enzymes and condensed, fragmented nuclei was observed in CdSNP-treated cells. Furthermore, the levels of interleukin-8, tumor growth factor and DNA fragmentation were significantly higher in CdSNP exposed cells. Data indicated that toxicity of CdSNP noted in A549 cells may be mediated through oxidative stress. This study warrants more comprehensive assessment of CdSNP prior to industrial applications.     

二氧化钛纳米颗粒与重金属联合毒性研究进展

二氧化钛纳米颗粒(Ti O2-NPs)在广泛使用的同时也带来了潜在的环境污染、生态和健康风险。随着Ti O2-NPs的废弃量逐年上升,其与环境中重金属的联合毒性特别是对生态环境的影响逐渐引起国内外研究者重视。结合近几年国内外对二者相互作用的研究,重点综述Ti O2-NPs与铅(Pb)、镉(Cd)和砷(As)之间的联合毒性,并对存在的问题和今后的关注重点进行探讨。     

全氟辛烷基磺酸钾(PFOS)和纳米氧化锌(Nano-ZnO)复合暴露对斑马鱼下丘脑-垂体-甲状腺轴功能的影响

全氟辛烷基磺酸钾(PFOS)和纳米氧化锌(Nano-Zn O)广泛存在于环境中,但是它们复合暴露对水生生物的潜在毒性机制尚未明确。本文探讨PFOS和Nano-Zn O复合暴露对斑马鱼下丘脑-垂体-甲状腺轴(HPT轴)毒性的影响。将斑马鱼胚胎从孵化开始暴露于PFOS(0.2、0.4、0.8 mg·L~(-1))、Nano-Zn O(6.75、12.5、25 mg·L~(-1))、PFOS+Nano-Zn O(0.2+6.75、0.4+12.5、0.8+25 mg·L~(-1))溶液中15 d后,分析幼鱼的发育毒性,体内的甲状腺激素(甲状腺素(T4)和三碘甲状腺氨酸(T3)含量和与甲状腺有关基因(CRF、TSH、NIS、TG和TPO)的表达情况。结果发现复合暴露组与单独暴露组相比,前者显著诱导了幼鱼的畸形率,降低了幼鱼的存活率,并抑制了幼鱼的体长。复合暴露组显著增加了幼鱼体内T3含量,同时抑制体内T4的含量。与单独暴露组相比,复合暴露组显著诱导了CRF和NIS基因的表达,同时抑制了TSHβ和TG基因的表达。而TPO基因的表达水平在单独和复合暴露组中没有显著差异。本研究首次证明了PFOS和Nano-Zn O复合暴露对斑马鱼幼鱼甲状腺轴的干扰效果并对其进行了机制探讨。     

双酚A对纳米二氧化钛理化特性及其DNA损伤效应的影响

纳米二氧化钛(nano-Ti O2)应用领域广泛,由于其对有机物或生物分子有吸附作用,二者相互反应,对各种细胞可能产生与nano-Ti O2单独作用时不同的毒性作用。为探讨双酚A(BPA)对nano-Ti O2理化性质的影响,以及BPA和nano-Ti O2联合暴露对人胚肝L-02细胞的DNA损伤效应。用不同缓冲液,测定不同浓度的BPA(0、0.1、1、10 mol·L-1)对不同浓度nano-Ti O2(0、0.1、1、10 mg·L-1)的粒径、表面电位和吸附能力的影响;然后测定不同浓度BPA和nano-Ti O2联合暴露对人胚肝L-02细胞DNA双链断裂、DNA损伤关键修复酶h Msh2基因(h Msh2)、O6-甲基鸟嘌呤甲基转移酶(MGMT)和DNA依赖蛋白激酶复合物催化亚基(DNA-PKcs)的m RNA表达水平表达的影响。结果表明在不同缓冲液中,随着BPA浓度的增加,nano-Ti O2粒径增加,表面电位上升,在细胞培养液DMEM中这一变化趋势最为明显;但在不同缓冲液中nano-Ti O2对BPA的吸附能力无明显差异。单独nano-Ti O2暴露不引起DNA双链断裂,对DNA损伤修复关键酶的表达也无明显影响,但nano-Ti O2可加重BPA的DNA双链断裂效应。与相应剂量的BPA单独染毒组比较,nano-Ti O2与BPA混合染毒组的细胞DNA双链断裂损伤加重(P0.05),h Msh2、MGMT和DNA-PKcs的基因表达水平明显上升(P0.05)。上述研究结果显示BPA可促进nano-Ti O2团聚,但团聚的nano-Ti O2仍可吸附BPA。单独nano-Ti O2暴露无DNA损伤作用,但nano-Ti O2可加重BPA的DNA双链断裂效应。其中h MSH2、MGMT和DNA-PKcs都参与2种污染物联合暴露所致的DNA损伤修复。     

纳米银和银离子对斑马鱼胚胎早期生长发育的影响及作用机制

为探究纳米银对水生生物的毒性作用,选取斑马鱼胚胎为受试生物,考察了纳米银对斑马鱼胚胎早期生长发育的影响,同时比较了纳米银与银离子对斑马鱼胚胎的毒性作用和机理。实验将受精后4小时(4 hpf)的斑马鱼胚胎分别暴露于不同浓度的纳米银和银离子溶液中至96 hpf,观察并记录了胚胎的死亡、孵化和畸形等指标。应用吖啶橙(AO)染色实验研究了胚胎暴露之后的细胞凋亡情况,并且应用荧光定量PCR技术分析了相关基因的表达水平。研究结果表明,随着暴露浓度的增加,纳米银和银离子均能导致斑马鱼胚胎的死亡率增加和孵化率降低,并且引起孵化延迟。纳米银和银离子的96 h半数致死浓度(96 h-LC50)分别为11.75 mg·L-1和0.054 mg·L-1。银离子毒性远大于纳米银毒性。暴露的斑马鱼胚胎均表现出体长变短和卵黄囊肿大的畸形。AO染色结果表明,纳米银和银离子处理组胚胎的躯干和卵黄囊部位存在细胞凋亡信号。基因表达分析结果显示,1.93 mg·L-1纳米银显著提高了斑马鱼胚胎caspase9的表达(P0.05),而0.006 mg·L-1的银离子就能显著上调COX-2a(P0.01)和COX-17(P0.05)基因的表达,同时0.036 mg·L-1银离子增加了斑马鱼体内p53基因的表达(P0.05)。以上研究结果说明,纳米银可能通过caspase通路诱导细胞凋亡进而影响斑马鱼胚胎的生长发育;而银离子不但影响氧化系统基因通路,还能通过p53诱导凋亡进而阻滞斑马鱼胚胎的生长发育。     

Pd/CMK-3的合成、表征及对甲酸的电催化氧化性能研究

以中孔硅SBA-15为硬模板、蔗糖为炭源,合成了有序中孔炭CMK-3,并以此CMK-3为载体,采用络合还原法制备了负载量为20%的催化剂Pd/CMK-3.X射线衍射(XRD)和透射电镜(TEM)的结果表明,CMK-3孔结构高度有序,呈现二维六方结构,Pd/CMK-3和Pd/AC(活性炭)催化剂中Pd纳米颗粒分散均匀,平均粒径分别为4.2 nm和4.5 nm;拉曼光谱测试表明,CMK-3比活性炭的石墨化程度更高,导电性更强;N2吸附/脱附实验表明,CMK-3具有典型的中孔结构,CMK-3的最可几孔径为4.5 nm,显著大于活性炭的0.54 nm,CMK-3的BET比表面积为1 114 m2.g-1,大于活性炭的871 m2.g-1.在对甲酸电催化氧化的循环伏安(CV)和计时电流(CA)测试中,Pd/CMK-3的初始催化活性显著高于Pd/AC,而两者在100 s后的计时电流稳定性则基本相当.     

原位植入TiO2纳米颗粒改性聚砜超滤膜及其抗生物污染性能研究

选用TiO_2纳米颗粒通过原位植入法对聚砜超滤膜表面进行改性,通过调节p H及沉淀浴中TiO_2浓度制备出不同TiO_2覆盖率的改性聚砜超滤膜,并分别用扫描电子显微镜、接触角测定仪、激光共聚焦显微镜等对改性膜性能进行评价.结果表明,p H为4时TiO_2分散良好并植入到聚砜膜表面,改变沉淀浴的浓度可以有效控制TiO_2在聚砜膜表面的覆盖率.聚砜膜的亲水性随TiO_2覆盖率的提高而不断增强.在纯水通量下降不明显的情况下,TiO_2改性超滤膜的抗生物污染性能均优于未改性膜,随着覆盖率的提高,抗生物污染性能呈现先增强后减弱的趋势,在覆盖率介于22.4%~27.7%之间时改性膜具有最优的抗生物污染性能,可使微生物粘附减少93%,黑暗培养24 h的生物膜厚度减少70%以上.