Synthesis of Cysteine-Functionalized Silver Nanoparticles Using Green Tea Extract with Application for Lipase Immobilization

The application of cysteine-capped silver nanoparticles synthesized using green tea as the reducing agent to immobilize lipase has been reported in the present work. The reducing property of green tea is due to the presence of polyphenolic compounds in its extract which are not oxidized at ambient atmospheric conditions and hence is a suitable reducing agent for green synthesis of nanoparticles. Cysteine-capped silver nanoparticles were synthesized under alkaline conditions by reducing the silver salt by green tea extract in the presence of cystine. Various parameters such as the cystine concentration, pH, temperature, and amount of reducing agent were standardized and their effect on the synthesis process has been initially evaluated by surface plasmon resonance peak analysis. Furthermore, the synthesized nanoparticles were also characterized using X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The particle size analysis revealed the average size of the particles to be around 20?nm. The glutaraldehyde-deactivated amino group on cysteine-capped nanoparticles was used to immobilize lipase on its surface. Both crude and immobilized lipases were checked for activity and protein content under standard assay conditions and their activity was found to be 37.7 and 24.9?U?mL^?1, respectively. The lipase nanoparticle bioconjugates exhibited a good shelf life of 60 days with a marginal decrease in activity. The bioconjugates showed 15% loss in its initial activity at the end of five reusability cycles. This immobilized reusable system has the potential to be utilized for various applications pertaining to the exploitation of lipase in various industries.     

Modified Polymer for Enzyme Immobilization and Characterization of Immobilized Urease

Abstract

Poly-γ-methyl-L-glutamate was modified by the introduction of -CC1₃ and /or -NH₂ groups. Two kinds of polymer were obtained, and applied to urease immobilization. The enzyme immobilized on polymer containing -CCl₃ (PCCl₃) pendant groups retained more activity than that containing -NH₂ (PNH₂). Stability of urease immobilized on PCCl₃ and PNH₂ was 17 days and 19 days respectively.     

Synthesis,Characterization and Antimicrobial Activity of Zinc Oxide Nanoparticles against Selected Waterborne Bacterial and Yeast Pathogens

The disinfection of wastewater using nanoparticles (NPs) has become a focal area of research in water treatment. In this study, zinc oxide (ZnO) NPs were synthesized using the microwave heating crystallization technique and characterized using transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD). Qualitative well diffusion and quantitative minimum inhibitory concentration (MIC) tests were conducted to determine the antimicrobial activity of ZnO NPs against selected waterborne pathogenic microbes. FTIR spectral studies confirmed that the binding of urea with Zn occurs through Zn–O stretching. XRD confirmed the crystallized identity in a hexagonal ZnO wurtzite-type structure. The formation of zones of inhibition and low MIC values in the antimicrobial analysis were indicative of the effective antimicrobial activity of zinc oxide nanoparticles against the test microorganisms. The application of metallic nanoparticles in water treatment could curb the spread of waterborne microbial diseases.     

Controllable Synthesis and Optical Properties of Connected Zinc Oxide Nanoparticles

Connected zinc oxide (ZnO) nanoparticles are successfully synthesized by a simple solution‐based chemical route that uses evaporation and concentration technology. The influences of processing parameters, especially the evaporation and concentration time on the size and morphology of the nanoparticles, have been investigated by transmission electron microscopy (TEM) and high‐resolution TEM (HRTEM). The structure and optical properties are systematically characterized by X‐ray diffraction (XRD), UV/Vis spectrophotometery, and fluorescence spectroscopy (FL). It is found that the average diameter and morphology are strongly affected by the evaporation and concentration time. Additionally, the formation mechanism of the nanoparticles is also discussed. The studies revealed that the evaporation and concentration are important aggregation or nucleation processes for ZnO growth, which leads to the macro‐differences in morphology. These results provide some insight into the growth mechanism of ZnO nanostructures. The synthetic strategy developed in this study may also be extended to the preparation of other nanomaterials and promising applications in various fields of nanotechnology.     

二氧化硅纳米与微米颗粒作为固定化酶载体的生物效应

分别将二氧化硅纳米颗粒(SiNPs)与微米颗粒(SiMPs)作为固定化载体, 选择多聚酶牛肝过氧化氢酶(CAT)和单体酶辣根过氧化物酶(HRP)作为酶模型, 通过考察酶固定化后在酶活回收率、热稳定性、 酶促反应最适温度以及酶在水-有机溶剂混合体系中催化能力的变化, 对载体与酶所产生的生物效应差异进行了系统研究. 酶活回收率结果表明, SiNPs显示出比SiMPs优越的对酶无选择性的高生物亲和性, 而SiMPs则能使固定于其上的酶热稳定性大幅度提高, 且二者都能使固定化酶在有机相中的稳定性得到明显增强. 但酶促反应最适温度的变化结果表明, 对不同类型的酶所产生的生物效应则表现出无规律性.     

Rubus Capped Zinc Oxide Nanoparticles Induce Apoptosis in MCF-7 Breast Cancer Cells

Rubus fairholmianus (RF) has widely been used to treat various ailments, including pain, diabetes, and cancer. Zinc oxide nanoparticles (ZnO NPs) have drawn attention in modern healthcare applications. Hence, we designed this study to synthesize zinc oxide (ZnO) nanoparticles using R. fairholmianus root extract to investigate its synergistic cytotoxic effect on MCF-7 cells and explore the possible cell death mechanism. ZnO NPs were synthesized via green synthesis using R. fairholmianus root extract, and the effect on MCF-7 cells was determined by looking at cellular morphology, proliferation, cytotoxicity, apoptosis, and reactive oxygen species (ROS). The results showed that cellular proliferation was reduced following treatment with R. fairholmianus capped zinc oxide nanoparticles (RFZnO NPs), while cytotoxicity and ROS were increased. There was also an increase in apoptosis as indicated by the significant increase in cytoplasmic cytochrome c and caspase 3/7 (markers of apoptosis), as well as increased levels of pro-apoptotic proteins (p53, Bax) and decreased levels of anti-apoptotic protein (Bcl-2). In conclusion, these results showed that RFZnO NPs induce apoptosis in breast cancer cells via a mitochondria-mediated caspase-dependent apoptotic pathway and suggest the use of acetone root extract of R. fairholmianus for the treatment of cancer-related ailments.     

Synthesis of Zinc Oxide Nanoparticles Using Rubus fairholmianus Root Extract and Their Activity against Pathogenic Bacteria

Recently, the biosynthesis of zinc oxide nanoparticles (ZnO NPs) from crude extracts and phytochemicals has attracted much attention. Green synthesis of NPs is cost-effective, eco-friendly, and is a promising alternative for chemical synthesis. This study involves ZnO NPs synthesis using Rubus fairholmianus root extract (RE) as an efficient reducing agent. The UV spectrum of RE-ZnO NPs exhibited a peak at 357 nm due to intrinsic bandgap absorption and an XRD pattern that matches the ZnO crystal structure (JCPDS card no: 36-1451). The average particle size calculated from the Debye–Scherrer equation is 11.34 nm. SEM analysis showed that the RE-ZnO NPs spherical in shape with clusters (1–100 nm). The antibacterial activity of the NPs was tested against Staphylococcus aureus using agar well diffusion, minimum inhibitory concentration, and bacterial growth assay. The R. fairholmianus phytochemicals facilitate the synthesis of stable ZnO NPs and showed antibacterial activity.     

纳米氧化锌的合成与表征

纳米氧化锌的合成与表征何勇宁，沈孝良，马礼敦（复旦大学分析测试中心上海２００４３３）关键词纳米材料，氧化锌，合成，表征制备纳米材料的方法很多，如蒸发冷凝法、化学气相沉积法、溶胶－凝胶法、超临界法、水热法及各种热分解法等。Ｌｉｕ等［２］用超声雾化热分解...     

纳米晶构筑一维多孔氧化锌的合成与表征

One-dimensional porous zinc oxide was prepared via the calcination of zinc oxalate precursor obtained by solvothermal method. The products were characterized by XRD, SEM, TEM, photoluminescence (PL) spectrum and nitrogen adsorption-desorption. The results show that the obtained zinc oxide sample is porous and constructed by nanoparticles about 30 nm in size. The specific surface area and total pore volume are 126 m²·g^-1 and 0.13 cm³·g^-1, respectively． The PL properties related with defects in ZnO nanoparticles were discussed for porous zinc oxide samples.     

Synergistic Effect between Amoxicillin and Zinc Oxide Nanoparticles Reduced by Oak Gall Extract against Helicobacter pylori

Helicobacter pylori (H. pylori) is a global health threat, and the World Health Organization has included H. pylori among 12 bacterial species that require high priority future strategies for the development of new antibiotics due mainly to its high rates of resistance. Metallic nanoparticles are known for their antimicrobial properties. The FDA (Food and Drug Administration) has approved zinc oxide nanoparticles (ZnONPs) as biocompatible antimicrobials. Green synthesis of ZnONPs was performed based on Oak galls extract (OGE) and was characterized by UV, IR, DLS, TEM, and SEM measurements. In addition, LC-MS/MS was used for the identification of OGE constituents. A checkerboard assay was used to evaluate the activity of synthesized Qi-ZnONPs and OGE against H. pylori, and their synergistic effects with amoxicillin were evaluated. LC-MS/MS analyses identified 20 compounds as major gallic acid conjugates. The ZnONPs had average particle sizes of 5.5 nm (DLS) and 7.99 nm (TEM). Both OGE and Qi-ZnONPs exhibited moderate activity against H. pylori. Amoxicillin and Qi-ZnONPs combinations (1:2 and 1:4 amoxicillin:/Qi-ZnONPs) significantly decreased the MIC₉₀ by two-fold and four-fold, respectively, and FIC values for the combinations were more significant than with OGE alone. OGE is rich in phenolics. The synergism between Qi-ZnONPs and amoxicillin can provide an alternative safe agent of low cost to combat H. Pylori infections.     

铟锡氧化物(ITO)纳米颗粒的制备及表征

以金属In和SnCl₄·5H₂O为主要原料，加入保护剂PVP，利用化学共沉淀法合成了球形的铟锡氧化物(ITO)纳米颗粒。分别对PVP的用量、溶液的pH值、热处理温度等因素对ITO纳米颗粒粒径的影响进行了分析。并且借助透射电镜(TEM)、X射线衍射(XRD)对所合成的ITO纳米颗粒进行了表征。XRD分析说明本文合成了金刚砂型结构的铟锡氧化物纳米颗粒，并且其晶型结构随着热处理温度的升高而转变为铁锰矿型。     

Manganese Oxide Nanoparticles/Reduced Graphene Oxide as Novel Electrochemical Platform for Immobilization of FAD and its Application as Highly Sensitive Persulfate Sensor

In this study, manganese oxide nanoparticles/reduced graphene oxide(MnOxNPs/rGO) was used as support for strong immobilization of flavin adenine dinucleotide(FAD). A thin film of rGO cast on the electrode surface, followed by performing electrodeposition of MnOxNPs at applied constant potential of +1.4 V vs. Ag/AgCl for 200 s. Finally, FAD was electrodeposited onto the rGO/MnOxNPs film by potential cycling between 1.0 to ?1.0 V in solution containing 1 mg ml^?1 FAD. Electrochemical properties and catalytic activity of GCE/rGO‐MnOxNPs/FAD toward persulfate (S₂O₈^2?) reduction was investigated. Under optimized condition, the concentration calibration range, detection limit, and sensitivity were 0.1 μM–2 mM, 90 nM and 125.8 nA/μM, respectively, using hydrodynamic amperometry technique.     

磁性铁氧化物纳米粒子表面功能化及其应用

表面功能化的磁性铁氧化物纳米粒子是一种新型功能材料,可应用于各种生物活性物质如蛋白质、DNA等的富集和分离,药物的磁靶向,以及疾病的诊断和治疗等许多领域.本文在总结近年来国内外有关功能化磁性铁氧化物纳米粒子研究成果的基础上,阐述了功能化磁性铁氧化物纳米粒子的结构类型、特点、目前的各种功能化制备方法以及相关应用最新研究进展,指出了当前研究中的主要发展方向和仍需要解决的问题.     

微接触印刷技术转移Au纳米粒子及氧化石墨烯复合图案及其性质研究

通过改良的“Hummers方法”制得氧化石墨烯,利用聚二甲基硅氧烷（PDMS）弹性印章的微接触印刷技术,以Au膜和氧化石墨烯溶液为“墨水”,通过二次印章转移,分别将Au纳米粒子和氧化石墨烯（Graphene Oxide,GO）转移至修饰了(3-氨基丙基)三乙氧基硅烷（APTES）的ITO基底（APTES/ITO）表面. 利用场发射扫描电子显微镜（FE-SEM）、原子力显微镜（AFM）等表征图案,结果表明转移的AuNPs和GO组成的复合图案均匀,致密性较好. 利用表面电势显微镜（Surface Potential Microscope,SEPM,KFM）测定了各部分的表面电势,以APTES/ITO基底表面为表面电势零点,各部分表面电势大小为：APTES/ITO > GO > Au（0,-11.6,-44.2 mV）.     

Selectivity in the Ligand Functionalization of Photocatalytic Metal Oxide Nanoparticles for Phase Transfer and Self-Assembly Applications

The functionalization of photocatalytic metal oxide nanoparticles of TiO₂, ZnO, WO₃ and CuO with amine-terminated (oleylamine) and thiol-terminated (dodecane-1-thiol) alkyl-chain ligands was studied under ambient conditions. A high selectivity was observed in the binding specificity of a ligand towards nanoparticles of these different oxides. It was observed that oleylamine binds stably to only TiO₂ and WO₃, whereas dodecane-1-thiol binds stably only to ZnO and CuO. Similarly, polar-to-nonpolar solvent phase transfer of TiO₂ and WO₃ nanoparticles could be achieved by using oleylamine, but not dodecane-1-thiol, whereas the opposite holds for ZnO and CuO. The surface chemistry of ligand-functionalized nanoparticles was probed by attenuated total reflectance (ATR)-FTIR spectroscopy, which enabled the occupation of the ligands at the active sites to be elucidated. The photostability of the ligands on the nanoparticle surface was determined by the photocatalytic self-cleaning properties of the material. Although TiO₂ and WO₃ degrade the ligands within 24 h under both UV and visible light, ligands on ZnO and CuO remain unaffected. The gathered insights are also highly relevant from an application point of view. As an example, because the ligand-functionalized nanoparticles are hydrophobic in nature, they can be self-assembled at the air-water interface to give nanoparticle films with demonstrated photocatalytic as well as anti-fogging properties.     

Effect of Zinc Oxide on Morphology and Mechanical Properties of Polyoxymethylene/Zinc Oxide Composites

This paper studies the effects of zinc oxide (ZnO) on morphology and mechanical properties of pure polyoxymethylene (POM) and POM/ZnO composites. POM/ZnO composites with varying concentration of ZnO were prepared by melt mixing technique in a twin screw extruder. The dispersion of ZnO particles on POM composites was studied by scanning electron microscope (SEM). It is observed that the dispersion of ZnO particles is relatively good. The mechanical properties of the composites such as tensile strength, stress at break, Young's modulus and impact strength were measured. Increasing content of ZnO up to 4.0 wt% increases the impact strength of POM. Addition of ZnO beyond 4.0 wt% decreases the impact strength. The composites containing ZnO content greater than 2.0 wt% show increased Young's Modulus. The tensile strength and stress at break decrease with increasing ZnO content. This may be due to the compatibility between ZnO and POM.     

反胶束法合成氧化锌微晶及其荧光特性

0引言材料的结构(微结构)、尺寸和形貌等因素对其特性及其实际应用具有重要的影响。对无机材料特别是氧化物半导体进行结构控制的研究近年来引起了人们极大的关注。氧化锌作为一种宽带隙(3.2eV)半导体材料,可广泛应用于压电材料、气体传感器、橡胶添加剂和光学器件等领域,而且还因其在室温下可产生激射现象使其成为纳米光学材料研究领域中的一大热点[1￣6]。目前,除了传统的固相-气相(V S)反应外,用于氧化锌微晶的制备方法主要有共沉淀法[7]、多羟基化合物水解法[8]、有机金属气相沉积法[9￣12]和水热法[13]等。通过选择不同的制备方法和…