Structure and activity of apoferritin-stabilized gold nanoparticles

A simple method for synthesizing gold nanoparticles stabilized by horse spleen apoferritin (HSAF) is reported using NaBH(4) or 3-(N-morpholino)propanesulfonic acid (MOPS) as the reducing agent. AuCl(4)(-) reduction by NaBH(4) was complete within a few seconds, whereas reduction by MOPS was much slower; in all cases, protein was required during reduction to keep the gold particles in aqueous solution. Transmission electron microscopy (TEM) showed that the gold nanoparticles were associated with the outer surface of the protein. The average particle diameters were 3.6 and 15.4 nm for NaBH(4)-reduced and MOPS-reduced Au-HSAF, respectively. A 5-nm difference in the UV-Vis absorption maximum was observed for NaBH(4)-reduced (530 nm) and MOPS-reduced Au-HSAF (535 nm), which was attributed to the greater size and aggregation of the MOPS-reduced gold sample. NaBH(4)-reduced Au-HSAF was much more effective than MOPS-reduced Au-HSAF in catalyzing the reduction of 4-nitrophenol by NaBH(4), based on the greater accessibility of the NaBH(4)-reduced gold particle to the substrate. Rapid reduction of AuCl(4)(-) by NaBH(4) was determined to result in less surface passivation by the protein. Methods for studying ferritin-gold nanoparticle assemblies may be readily applied to other protein-metal colloid systems.     

Preparation and antibacterial activity of chitosan nanoparticles

Chitosan nanoparticles, such as those prepared in this study, may exhibit potential antibacterial activity as their unique character. The purpose of this study was to evaluate the in vitro antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against various microorganisms. Chitosan nanoparticles were prepared based on the ionic gelation of chitosan with tripolyphosphate anions. Copper ions were adsorbed onto the chitosan nanoparticles mainly by ion-exchange resins and surface chelation to form copper-loaded nanoparticles. The physicochemical properties of the nanoparticles were determined by size and zeta potential analysis, atomic force microscopy (AFM), FTIR analysis, and XRD pattern. The antibacterial activity of chitosan nanoparticles and copper-loaded nanoparticles against E. coli, S. choleraesuis, S. typhimurium, and S. aureus was evaluated by calculation of minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). Results show that chitosan nanoparticles and copper-loaded nanoparticles could inhibit the growth of various bacteria tested. Their MIC values were less than 0.25 microg/mL, and the MBC values of nanoparticles reached 1 microg/mL. AFM revealed that the exposure of S. choleraesuis to the chitosan nanoparticles led to the disruption of cell membranes and the leakage of cytoplasm.     

Morphology and antibacterial activity of carbohydrate-stabilized silver nanoparticles

Silver nanoparticles were prepared by a simple hydrothermal route and chemical reduction using carbohydrates (sucrose, soluble and waxy corn starch) as reducing as well as stabilizing agents. The crystallite size of these nanoparticles was evaluated from X-ray diffraction (XRD) and transmission electron microscopy (TEM) and was found to be 25 nm. The effect of carbohydrates on the morphology of the silver nanocomposites was studied using scanning EM (SEM). The nanocomposites exhibited interesting inhibitory as well as bactericidal activity against both Gram positive and Gram negative bacteria. Incorporation of silver also increased the thermal stability of the carbohydrates.     

Magnetic single-enzyme nanoparticles with high activity and stability

Magnetic single-enzyme nanoparticles (SENs) encapsulated within a composite inorganic/organic polymer network were fabricated via the surface modification and in situ aqueous polymerization of separate enzyme molecule. The resultant nanoparticles were characterized by transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectrometer and X-ray diffraction (XRD). These particles are almost spherical in shape and have a unique size of about 50 nm in diameter. Electrical and magnetic measurements reveal that the magnetic SENs have a conductivity of 2.7 × 10⁻³ S cm⁻¹, and are superparamagnetic with a saturation magnetization of 14.5 emu g⁻¹ and a coercive force of 60 Oe. Compared with free enzyme, encapsulated enzyme exhibits a strong tolerance to the variation of solution pH, high temperature, organic solvent and long-term storage, thus showing significantly enhanced enzyme performance and stability.     

Ag-SiO_2核壳型纳米粒的制备及其抗菌作用

利用抗坏血酸对AgNO3进行还原,生成银纳米粒核心,并通过正硅酸四乙酯的水解与聚合反应获得SiO2介孔外壳,制备平均粒径约为92.9 nm的Ag-SiO2核-壳型纳米粒。Ag-SiO2纳米粒可以显著地抑制香石竹镰刀菌的生长,最小抑菌质量浓度为4μg/mL,并可抑制香石竹镰刀菌菌丝生长和孢子分生。Ag-SiO2纳米粒处理2~4 h后,菌丝体的过氧化氢酶、总超氧化物歧化酶、过氧化物酶活力增强,提示Ag-SiO2纳米粒抗菌机制和活性氧诱导相关。     

In vivo antitumor activity of chitosan nanoparticles

Chitosan nanoparticles have been synthesized as potential anticancer agents, and evaluated, in vitro, against various cancer cell lines. In this study, in vivo antitumor activity of chitosan nanoparticles against Sarcoma-180 and mouse hepatoma H22 was investigated. Chitosan nanoparticles showed significant antitumor activity in vivo. The doses and particle size made a great effect on their efficacy.     

Cytotoxicity and trypanocidal activity of nifurtimox encapsulated in ethylcyanoacrylate nanoparticles

The aim of the present study was to study the trypanocidal activity of nanoparticles loaded with nifurtimox in comparison with the free drug against Trypanosoma cruzi, responsible for Chagas' disease. Ethylcyanoacrylate nanoparticles acted as the delivery system into cells. As the obligate replicative intracellular form is amastigote, in vitro studies were performed on this form of parasite as well as on cell culture derived trypomastigotes. The fluorescence method used here was very useful as it allowed for the simultaneous study of trypanocide activity and cytotoxicity by determining living or dead parasites within living or dead host cells. According to these results, the greatest trypanocide activity on cell culture-derived trypomastigotes was recorded for nifurtimox-loaded nanoparticles with a 50% inhibitory concentration (IC50) twenty times less than that of the free drug. The cytotoxicity of unloaded nanoparticles at low concentrations was similar to that obtained by free drug when evaluated on Vero cells. Furthermore, nifurtimox-loaded nanoparticles showed increased trypanocide activity on intracellular amastigotes with an IC50 thirteen times less than that of nifurtimox. We also observed that the unloaded nanoparticles possess the previously-described trypanocide activity, similar to the standard solution of nifurtimox, although the mechanism for this has not yet been elucidated. In conclusion, it was possible to establish in vitro conditions using nifurtimox encapsulated nanoparticles in order to decrease the doses of the drug and thus to obtain high trypanocidal activity on both free trypomastigotes and intracellular amastigotes with low cytotoxicity for the host cell.     

The synthesis of chitosan-based silver nanoparticles and their antibacterial activity

Chitosan-based silver nanoparticles were synthesized by reducing silver nitrate salts with nontoxic and biodegradable chitosan. The silver nanoparticles thus obtained showed highly potent antibacterial activity toward both Gram-positive and Gram-negative bacteria, comparable with the highly active precursor silver salts. Silver-impregnated chitosan films were formed from the starting materials composed of silver nitrate and chitosan via thermal treatment. Compared with pure chitosan films, chitosan films with silver showed both fast and long-lasting antibacterial effectiveness against Escherichia coli. The silver antibacterial materials prepared in our present system are promising candidates for a wide range of biomedical and general applications.     

钩状木霉生物合成纳米银及其杀菌性能

【目的】以钩状木霉为微生物材料合成纳米银粒子,并对其杀菌性能进行测定。【方法】将钩状木霉与2 mmol/L的Ag NO3溶液混合暗培养合成纳米银,采用UV-vis、XRD和TEM等方法对纳米银进行表征;利用原子吸收光谱仪和热重分析仪测定并计算银离子的转化率和纳米银的产率;以大肠杆菌和枯草芽孢杆菌为受试菌株检测纳米银的杀菌性能。【结果】钩状木霉与硝酸银混合的培养液颜色为红褐色,UV-vis图谱显示在420 nm左右出现了强的吸收峰;XRD图谱出现了4个特征性衍射峰,分别对应纳米银的4个晶面;TEM照片可以看出纳米银多数为球形,具有单分散性;粒度分布仪显示纳米银具有很窄的粒径分布,在1-13 nm之间,平均粒径为6.69 nm;根据原子光谱吸收仪测定的结果得到银的转化率为84.41%,根据热重分析结果得到纳米银的产率为67.12%;纳米银对大肠杆菌的MBC为10 mg/L,MIC为7 mg/L;对枯草芽孢杆菌的MBC为5 mg/L,MIC为4 mg/L。【结论】钩状木霉与Ag NO3溶液混合培养可以合成纳米银。合成的纳米银大小均匀,粒径小且分布很窄,具有面心立方结构,是纯净的,产率约为67.12%;纳米银对枯草芽孢杆菌的致死效果好于对大肠杆菌的致死效果。     

Antibacterial activity and mechanism of silver nanoparticles on Escherichia coli

The antibacterial activity and acting mechanism of silver nanoparticles (SNPs) on Escherichia coli ATCC 8739 were investigated in this study by analyzing the growth, permeability, and morphology of the bacterial cells following treatment with SNPs. The experimental results indicated 10 μg/ml SNPs could completely inhibit the growth of 10⁷ cfu/ml E. coli cells in liquid Mueller–Hinton medium. Meanwhile, SNPs resulted in the leakage of reducing sugars and proteins and induced the respiratory chain dehydrogenases into inactive state, suggesting that SNPs were able to destroy the permeability of the bacterial membranes. When the cells of E. coli were exposed to 50 μg/ml SNPs, many pits and gaps were observed in bacterial cells by transmission electron microscopy and scanning electron microscopy, and the cell membrane was fragmentary, indicating the bacterial cells were damaged severely. After being exposed to 10 μg/ml SNPs, the membrane vesicles were dissolved and dispersed, and their membrane components became disorganized and scattered from their original ordered and close arrangement based on TEM observation. In conclusion, the combined results suggested that SNPs may damage the structure of bacterial cell membrane and depress the activity of some membranous enzymes, which cause E. coli bacteria to die eventually.     

Anti-biofilm activity of silver nanoparticles against different microorganisms

Biofilms confer protection from adverse environmental conditions and can be reservoirs for pathogenic organisms and sources of disease outbreaks, especially in medical devices. The goal of this research was to evaluate the anti-biofilm activities of silver nanoparticles (AgNPs) against several microorganisms of clinical interest. The antimicrobial activity of AgNPs was tested within biofilms generated under static conditions and also under high fluid shears conditions using a bioreactor. A 4-log reduction in the number of colony-forming units of Pseudomonas aeruginosa was recorded under turbulent fluid conditions in the CDC reactor on exposure to 100?mg?ml^?1 of AgNPs. The antibacterial activity of AgNPs on various microbial strains grown on polycarbonate membranes is reported. In conclusion, AgNPs effectively prevent the formation of biofilms and kill bacteria in established biofilms, which suggests that AgNPs could be used for prevention and treatment of biofilm-related infections. Further research and development are necessary to translate this technology into therapeutic and preventive strategies.     

Biosynthesis of silver nanoparticles using Malva parviflora and their antifungal activity

Cheeseweed mallow (Malva parviflora L.) was used to biosynthesize silver nanoparticles. The biosynthesized silver nanoparticles were classified by UV–vis Spectroscopy and Fourier-Transform Infrared Spectroscopy (FT-IR). The shape and size distribution were visualized by Transmission Electron Microscopy (TEM), Field Emission Scanning Electron Microscopy (FE-SEM), and Zeta potential analysis. The chemical composition of M. parviflora leaf extract was identified by Gas Chromatography and Mass Spectroscopy (GC/MS). Finally, in vitro antifungal assay was done to assess the potential of biosynthesized silver nanoparticles and crude leaf extract of M. parviflora for inhibiting the mycelial growth of phytopathogenic fungi. The UV–vis analysis manifests the formation of silver nanoparticles. FTIR analysis established that chemicals of the leaf extract stabilized the biosynthesized silver nanoparticles by binding with the free silver ions. The TEM, FE-SEM and zeta potential analyzer confirmed that the biosynthesized silver nanoparticles were mostly spherical with an average diameter of 50.6 nm. The biosynthesized silver nanoparticles and leaf extract of M. parviflora effectively mitigate the mycelial growth of Helminthosporium rostratum, Fusarium solani, Fusarium oxysporum, and Alternaria alternata. The maximum reduction in mycelial growth by biosynthesized nanoparticles was observed against H. rostratum (88.6%). Whereas, the leaf extract of M. parviflora was most effective against F. solani (65.3%). Thus, the biosynthesis of nanoparticle assisted by M. parviflora is a feasible and eco-friendly method for the synthesis of silver nanoparticles. Further the silver nanoparticles and leaf extract of M. parviflora could be explored for the development of the fungicide.     

Antimicrobial activity of Fe‐loaded chitosan nanoparticles

To increase the antimicrobial activities of chitosan, chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were prepared by surfactant‐assisted chitosan chelating Fe²⁺, Fe³⁺ and ionic gelation chitosan. Their chelating rates were determined by spectrophotometry. The particle sizes and zeta potentials of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were measured by size and zeta potential analysis. The nanoparticles antimicrobial activities were evaluated by different concentration against Escherichia coli, Staphylococcus aureus, Candida albicans in vitro. Results showed that the mean diameter of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ were 206.4 and 195.2 nm, respectively. Their zeta potentials were +28.82 and +28.26 mV, respectively. The chelating rate of chitosan nanoparticles loaded with Fe²⁺ was greatly higher than with Fe³⁺. Their antimicrobial activity was showed greatly higher at lower concentrations compared to chitosan, and the antibacterial effect of chitosan nanoparticles loaded with Fe²⁺ or Fe³⁺ was preliminary observed.     

Green synthesis of silver and gold nanoparticles using Zingiber officinale root extract and antibacterial activity of silver nanoparticles against food pathogens

In the present study, we synthesized silver and gold nanoparticles with a particle size of 10–20 nm, using Zingiber officinale root extract as a reducing and capping agent. Chloroauric acid (HAuCl₄) and silver nitrate (AgNO₃) were mixed with Z. officinale root extract for the production of silver (AgNPs) and gold nanoparticles (AuNPs). The surface plasmon absorbance spectra of AgNPs and AuNPs were observed at 436–531 nm, respectively. Optimum nanoparticle production was achieved at pH 8 and 9, 1 mM metal ion, a reaction temperature 50 °C and reaction time of 150–180 min for AgNPs and AuNPs, respectively. An energy-dispersive X-ray spectroscopy (SEM–EDS) study provides proof for the purity of AgNPs and AuNPs. Transmission electron microscopy images show the diameter of well-dispersed AgNPs (10–20 nm) and AuNPs (5–20 nm). The nanocrystalline phase of Ag and Au with FCC crystal structures have been confirmed by X-ray diffraction analysis. Fourier transform infrared spectroscopy analysis shows the respective peaks for the potential biomolecules in the ginger rhizome extract, which are responsible for the reduction in metal ions and synthesized AgNPs and AuNPs. In addition, the synthesized AgNPs showed a moderate antibacterial activity against bacterial food pathogens.     

Antimicrobial activity of stable silver nanoparticles of a certain size

Conditions for obtaining stable silver nanoparticles smaller than 10 nm were developed using a binary stabilizer polyvinylpyrrolidone/sodium dodecylsulphate in optimal ratio. Optical spectra, morphology and dependence of size of the nanoparticles on the amount of reducing agent were studied. Colloidal solutions of nanosilver showed a high bactericidal activity against strains of Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, and fungicidal activity against Candida albicans. The mechanism of action of nanosized silver on microbial cell was examined by laser scanning confocal microscope using fluorescent label. First step of antimicrobial effect on microorganisms was membrane damage and penetration of silver nanoparticles into the cell. Prolonged stability of nanoparticles and their antimicrobial activity over the past two years were showed.     

Biosynthesis and antibacterial activity of ZnO nanoparticles using Trifolium pratense flower extract

Zinc oxide (ZnO) has broad applications in various areas. Nanoparticle synthesis using plants is an alternative to conventional physical and chemical methods. It is known that the biological synthesis of nanoparticles is gaining importance due to its simplicity, eco-friendliness and extensive antimicrobial activity. Also, in this study we report the synthesis of ZnO nanoparticles using Trifolium pratense flower extract. The prepared ZnO nanoparticles have been characterized by UV–Vis absorption spectroscopy, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) with Energy dispersive X-ray analysis (EDX). Besides, this study determines the antimicrobial efficacy of the synthesized ZnO nanoparticles against clinical and standard strains of S. aureus and P. aeruginosa and standard strain of E. coli.