Fabrication of silver ion exchanged zeolite using scoria and its antibacterial activity

In this study, we examined the antibacterial activity of silver ion exchanged zeolite synthesized from Cheju Scoria. We synthesized zeolite in various NaOH concentrations, but zeolite synthesized in 4 M NaOH was most similar to type A zeolite. Using the synthesized zeolite, we prepared a silver ion exchanged zeolite for studies of antibacterial activity. Antibacterial tests using agar cultures of Escherichia coli (E. coli), with silver ion exchanged zeolite showed a zone of inhibition colonies bacteria did not grow near silver ion exchanged zeolite. Furthermore, spectrophotometry demonstrated a significantly low absorbance of E. coli culture mediums when silver ion exchanged zeolite was included indicating that E. coli propagation was prevented. Through results of these experiments, we conclude that synthesized products with sodalite crystal can be synthesized from Scoria, and these are suitable to produce silver ion exchanged zeolite with antibacterial activity.     

The antibacterial activity of biogenic silver and its mode of action

In a previous study, biogenic silver nanoparticles were produced by Lactobacillus fermentum which served as a matrix preventing aggregation. In this study the antibacterial activity of this biogenic silver was compared to ionic silver and chemically produced nanosilver. The minimal inhibitory concentration (MIC) was tested on Gram-positive and Gram-negative bacteria and was comparable for biogenic silver and ionic silver ranging from 12.5 to 50 mg/L. In contrast, chemically produced nanosilver had a much higher MIC of at least 500 mg/L, due to aggregation upon application. The minimal bactericidal concentration (MBC) in drinking water varied from 0.1 to 0.5 mg/L for biogenic silver and ionic silver, but for chemically produced nanosilver concentrations, up to 12.5 mg/L was needed. The presence of salts and organic matter decreased the antimicrobial activity of all types of silver resulting in a higher MBC and a slower inactivation of the bacteria. The mode of action of biogenic silver was mainly attributed to the release of silver ions due to the high concentration of free silver ions measured and the resemblance in performance between biogenic silver and ionic silver. Radical formation by biogenic silver and direct contact were found to contribute little to the antibacterial activity. In conclusion, biogenic nanosilver exhibited equal antimicrobial activity compared to ionic silver and can be a valuable alternative for chemically produced nanosilver.     

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.     

Synthesis and characterization of silver nanoparticles using Cynodon dactylon leaves and assessment of their antibacterial activity

Many methods of synthesizing silver nanoparticles (Ag-NPs) by reducing Ag⁺ ions using aqueous/organic extracts of various plants have been reported in the past, but the methods are rather slow. In this investigation, silver nanoparticles were quickly synthesized from aqueous silver nitrate through a simple method using leaf extract of a plant—Cynodon dactylon which served as reducing agent, while sunlight acted as a catalyst. The formation of Ag-NPs was indicated by gradual change in colour and pH and confirmed by ultraviolet–visible spectroscopy. The Ag-NPs showed a surface plasmon resonance at 451 nm. Based on the decrease in pH, a possible mechanism of the synthesis of Ag-NPs involving hydroxyl (OH^?) ions of polyphenols of the leaf extract is postulated. Ag-NPs having (111) and (200) crystal lattices were confirmed by X-ray diffraction. Scanning electron microscopy revealed the spherical nature of the Ag-NPs, while transmission electron microscopy showed that the nanoparticles were polydispersed with a size range of 8–10 nm. The synthesized Ag-NPs also demonstrated their antibacterial activity against Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Salmonella typhimurium.     

Assessment of antibacterial activity of silver nanoparticles on Pseudomonas aeruginosa and its mechanism of action

Antimicrobial activity of silver nanoparticles is gaining importance due its broad spectrum of targets in cell compared to conventional antimicrobial agents. In this context, a UV photo-reduction method was used for the synthesis and the nanoparticles were characterized by UV–Visible spectroscopy, transmission electron microscopy, atomic force microscopy and thermogravimetric analysis techniques. The antibacterial activity of the synthesized silver nanoparticles was evaluated both in liquid and solid growth media employing various susceptibility assays on Pseudomonas aeruginosa, a ubiquitous bacterium. The dose dependent growth suppression by nanoparticles was studied with well diffusion method. By broth dilution method, the minimum inhibitory concentration (MIC) was found to be 2 μg/ml. It was observed that the bactericidal effect depends both on nanoparticle concentration and number of bacteria present. In our study, we could demonstrate the complete antibiofilm activity of silver nanoparticles at a concentration as low as 1 μg/ml. Our observations substantiated the association of reactive oxygen species and cell membrane damage in the antibacterial mechanism of silver nanoparticles. Our findings suggested that these nanoparticles can be exploited towards the development of potential antibacterial coatings for various biomedical and environmental applications.     

Biogenic silver nanoparticle synthesis with cyanobacterium Chroococcus minutus isolated from Baliharachandi sea-mouth,Odisha, and in vitro antibacterial activity

The burden from microbial diseases has to be addressed in an increasing pace due to multidrug resistance, causing clinical annoyance, globally. Indeed, employing eco-friendly approaches by green syntheses of nanoparticles with metals/metalloids as antibacterial compounds would be continual and cost-effective. Herein, the synthesis of silver nanoparticles (AgNPs) by aqueous extracts of the cyanobacterium Chroococcus minutus (strain, CRLSUM10), collected from the meeting point of sea and river, East coast of India, are presented; both reducing and stabilizing mediators of the synthesized AgNPs were ascertained, by characteriztion by UV–visible spectrophotometry, XRD, FTIR, SEM and SEM-EDX. Furthermore, synthesized AgNPs had a remarkable antibacterial activity at the lowest dose, 100 mg against pathogenic strains of E. coli and S. pyogenes, rendering those as novel antibacterial agents against ‘upper respiratory tract infection’.     

Cellular radioprotecting potential of glyzyrrhizic acid, silver nanoparticle and their complex

Silver nanoparticles (SN) of particle size of less than 50nm were redispersed in aqueous solution of Pluronic F127 and complexed with the phytoceutical, glyzyrrhizic acid (GLY). Radioprotecting ability of the obtained nanoparticle-glyzyrrhizic acid complex (SN-GLY) was evaluated in an in vivo model using Swiss albino mice. Oral administration of SN-GLY, SN and GLY one hour prior to radiation exposure reduced the radiation induced damage in peripheral blood leucocytes, bone marrow cells and spleen cells of mice as revealed by comet assay. Exposure of mice to whole body gamma irradiation resulted in formation of micronuclei in blood reticulocytes and chromosomal aberrations in bone marrow cells while SN-GLY, SN or GLY administration resulted in reduction in micronucleus formation and chromosomal aberrations indicating radioprotection. In SN-GLY treated mice the cellular DNA was found protected to a greater extent compared to GLY or SN treated mice. The studies, under in vivo radiation exposure conditions, showed effective radiation protection.     

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。     

靶向α-酮戊二酸脱氢酶增强纳米银的抗菌作用

【目的】纳米银(silver nanoparticles, AgNPs)的生物安全性一直受业界诟病,扩大纳米银的治疗窗将为治疗人和动物多耐药性细菌感染提供有效的备选药物。本研究拟用三羧酸循环的重要成员α-酮戊二酸(alpha-ketoglutaric acid, AKG)对纳米银进行表面修饰以提高其抗菌的生物安全性。【方法】芦丁在常温下合成纳米银,用全波长分光光度计、粒度仪及透射电镜进行表征。加1 mmol/L聚乙烯吡咯烷酮(polyvinylpyrrolidone, PVP)作为稳定剂(PVP-AgNPs),另加10 mmol/L AKG作为封端剂(PVP-AgNPs@AKG),比较2种纳米银的抗菌性及对人正常宫颈上皮细胞(human cervical epithelial cells, HCerEpic)的毒性作用,再分析2种纳米银对大肠杆菌(Escherichia coli) BW25113能量代谢、抗氧化应激和无氧呼吸相关基因表达等的影响。【结果】PVP-AgNPs@AKG对多株革兰阳性细菌和革兰阴性细菌的最小抑菌浓度(minimal inhibit concentration, MIC)和最低杀菌浓度(minimum bactericidal concentration, MBC)均比PVP-AgNPs低50%或50%以上,而对HCerEpic细胞的毒性无显著差异。与PVP-AgNPs相比,PVP-AgNPs@AKG在MIC浓度下对E. coli α-酮戊二酸脱氢酶活性的抑制作用增强,AKG蓄积,ATP水平显著降低,同时活性氧(reactive oxygen species, ROS)的水平显著升高,soxS表达上调,但是,厌氧呼吸相关的arcA、fnr、fdnH基因表达上调的程度显著降低。【结论】AKG修饰纳米银能通过靶向α-酮戊二酸脱氢酶抑制细菌的能量代谢,使其对氧化损伤更敏感,从而获得更强的抗菌能力,是一种扩大纳米银治疗窗的有效手段。     

FT-IR and GC-MS analyses of potential bioactive compounds of cow urine and its antibacterial activity

The main emphasis of this study was to identify the bioactive compounds responsible for antibacterial activity of Badri cow urine isolated by thin layer chromatography. The most effective bioactive fraction was analysed by FT-IR and GC-MS analyses. Among the four major fractions (EW1, EW2, CA1 and CA2) obtained by TLC profiling, EW1 was found most active against bacterial strains viz., Listeria monocytogenes (MTCC657), Staphylococcus aureus (MTCC7443), Pseudomonas aeruginosa (MTCC424), Klebsiella pneumoniae (MTCC432) and Salmonella typhi (MTCC733). However, Escherichia coli (MTCC118), was found resistant to all the fractions. In FT-IR spectroscopy, functional groups like alcohol, amide, alkene, alkyl halide, polysulfide and phosphate ions were identified. The GC-MS analysis of EW1 fraction exhibited the presence of 12 compounds, of which 1-heneicosanol was found as the major compound. These compounds might be responsible synergistically or individually for antibacterial activity of cow urine. Nine elements namely sodium (Na), calcium (Ca), chromium (Cr), iron (Fe), magnesium (Mg), aluminium (Al), potassium (K) and zinc (Zn), Gold (Au) were measured by ICP-MS analysis.     

Biosynthesis of silver nanoparticles using Bacillus subtilis EWP-46 cell-free extract and evaluation of its antibacterial activity

This study highlights the ability of nitrate-reducing Bacillus subtilis EWP-46 cell-free extract used for preparation of silver nanoparticles (AgNPs) by reduction of silver ions into nano silver. The production of AgNPs was optimized with several parameters such as hydrogen ion concentration, temperature, silver ion (Ag⁺ ion) and time. The maximum AgNPs production was achieved at pH 10.0, temperature 60 °C, 1.0 mM Ag⁺ ion and 720 min. The UV–Vis spectrum showed surface plasmon resonance peak at 420 nm, energy-dispersive X-ray spectroscopy (SEM–EDX) spectra showed the presence of element silver in pure form. Atomic force microscopy (AFM) and transmission electron microscopy images illustrated the nanoparticle size, shape, and average particle size ranging from 10 to 20 nm. Fourier transform infrared spectroscopy provided the evidence for the presence of biomolecules responsible for the reduction of silver ion, and X-ray diffraction analysis confirmed that the obtained nanoparticles were in crystalline form. SDS-PAGE was performed to identify the proteins and its molecular mass in the purified nitrate reductase from the cell-free extract. In addition, the minimum inhibitory concentration and minimum bactericidal concentration of AgNPs were investigated against gram-negative (Pseudomonas fluorescens) and gram-positive (Staphylococcus aureus) bacteria.     

Purification of a lectin from Eugenia uniflora L. seeds and its potential antibacterial activity

Aims: The aim of this work was to analyse the antimicrobial properties of a purified lectin from Eugenia uniflora L. seeds. Methods and Results: The E. uniflora lectin (EuniSL) was isolated from the seed extract and purified by ion‐exchange chromatography in DEAE‐Sephadex with a purification factor of 11·68. The purified lectin showed a single band on denaturing electrophoresis, with a molecular mass of 67 kDa. EuniSL agglutinated rabbit and human erythrocytes with a higher specificity for rabbit erythrocytes. The haemagglutination was not inhibited by the tested carbohydrates but glycoproteins exerted a strong inhibitory action. The lectin proved to be thermo resistant with the highest stability at pH 6·5 and divalent ions did not affect its activity. EuniSL demonstrated a remarkable nonselective antibacterial activity. EuniSL strongly inhibited the growth of Staphylococcus aureus, Pseudomonas aeruginosa and Klebsiella sp. with a minimum inhibitory concentration (MIC) of 1·5 μg ml^?1, and moderately inhibited the growth of Bacillus subtilis, Streptococcus sp. and Escherichia coli with a MIC of 16·5 μg ml^?1. Conclusions: EuniSL was found to be effective against bacteria. Significance and Impact of the Study: The strong antibacterial activity of the studied lectin indicates a high potential for clinical microbiology and therapeutic applications.     

具有抗菌效应的聚羟基脂肪酸酯生物塑料的制备与功能表征

聚羟基脂肪酸酯(Polyhydroxyalkanoates,PHAs)作为一类新型的生物高分子材料,因其多样的材料性质与高度的生物可降解性日益受到关注。使用乳酸链球菌素(Nisin),一种被公认为安全的天然食品防腐剂,制备了具有高效、持久抗菌效应的PHA塑料。首先采用溶剂浇铸的方法将Nisin整合到正3-羟基丁酸-3羟基己酸共聚酯(PHBHHx),一种具备高度生物相容性的PHA中,从而获得了具有抗菌效应的PHBHHx薄膜。激光共聚焦显微镜观察表明Nisin在PHBHHx中呈颗粒状均匀分布。随后以条件致病菌藤黄微球菌Micrococcus luteus为测试菌株,通过琼脂扩散法,测定PHBHHx薄膜抗菌效应对Nisin含量的依赖关系;在液体培养条件下测量PHBHHx薄膜的Nisin释放效果与抗菌效应。结果表明Nisin可从PHBHHx薄膜顺利释放且Nisin的含量高于25μg/g时即表现出显著的抑菌效果且可长时间维持。该研究为工业化生产具有抗菌效应的PHA奠定了重要的技术基础,拓展了PHA在医学和食品领域的应用潜力。     

Eco-friendly synthesis of silver nanoparticles by Bacillus subtilis and their antibacterial activity

Bacillus subtilis was used for biogenic of silver nanoparticles. Characterization of the prepared silver nanoparticles was done by UV–Vis spectroscopy, Transmission Electron Microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FT-IR). The particle size of the prepared nanoparticles ranges from 3 to 20 nm with spherical or roughly spherical forms. The antimicrobial efficacy of the produced nanoparticles was investigated against five strains of multidrug resistant microorganisms including: Staphylococcus aureus (MRSA), Staphylococcus epidermidis, Klebsiella. pneumoniae, Escherichia coli and Candida albicans tested as yeast. During this study, the minimum inhibitory concentrations (MICs) and the minimum lethal concentrations (MLCs) of synthesized silver nanoparticles were detected using selected strains of the genus Bacillus by a broth dilution method. The rate of MIC of the prepared silver nano-particles versus the investigated clinical isolates exhibit a massive anti-microbial efficacy; (230 µgml⁻¹) for MRSA; 180 for Staphylococcus epidermidis, 200 for Escherichia coli and 100 µgml⁻¹ for Candida albicans. On the other hand, the lowest anti-microbial efficacy (300 µgml⁻¹) was appeared for Klebsiella pneumonia. The obtained results demonstrated the effectiveness of the biogenic nanoparticles and the possibility of using them as a new method in combating infectious diseases.     

Tetraploid induction of Mitracarpus hirtus L. by colchicine and its characterization including antibacterial activity

Tetraploid plants were successfully induced for the first time in Mitracarpus hirtus L., by overnight immersion of shoot meristems in 0.1 % colchicine solution, followed by in vitro culture leading to plant regeneration. Examination of ploidy level by flow cytometric analysis and counting chromosome number at metaphase confirmed that original diploid plant (WT1) contained chromosome number as 2n = 2x = 28, whereas 2n = 4x = 56 was observed in the tetraploids induced with colchicine treatment (CC102 and CC110). Thicker root formation, larger stomata (1.3–2 times), and lower density of stomata (1.7–4 times) were observed in these tetraploid plants. After transplantation to the pot, tetraploid plant (CC110) showed higher fresh weights of aerial part and leaves (1.5 and 1.4 times respectively) than diploid. However, the methanolic extracts from leaves of tetraploid line CC102 showed inhibition against human pathogenic bacterium, S. aureus while WT1 and CC110 showed no activity. GC–MS revealed 40 unique compounds present in CC102, but absent in WT1 and CC110. Through hierarchical clustering analysis the 40 unique compounds in CC102 formed a cluster group found to correlate with anti-S. aurens activity. These results suggested that tetraploid M. hirtus CC102 created in this study provides a novel source of compounds useful in fighting infectious disease.     

纳米银胶/壳聚糖复合抗菌剂的制备及其在洗涤产品中抗菌性能

本文研究了纳米银胶/壳聚糖抗菌剂的制备及其形貌的表征分析,以大肠杆菌为代表菌株,研究了复合抗菌剂在洗涤产品中的抗菌效率及抗菌的稳定性,结果说明复合抗菌剂在洗涤产品中添加1.0%时,其抗菌效率达99%,经180 d长期分析,其抗菌活性仍保持95%左右。此外,复合抗菌剂对不同菌株的抗菌性能也均较强。     

The effect of temperature on antibacterial activity of biosynthesized silver nanoparticles

The purpose of this study was the evaluation of two different temperatures on antibacterial activity of the biosynthesized silver nanoparticles. 38 silver nanoparticles-producing bacteria were isolated from soil and identified. Biosynthesis of silver nanoparticles by these bacteria was verified through visible light spectrophotometry. Two strains were relatively active for production of silver nanoparticles. These strains were subjected for molecular identification and recognized as Bacillus sp. and Acinetobacter schindleri. In the present study, the effect of temperatures was evaluated on structure and antimicrobial properties of the silver nanoparrticles by transmission electron microscopy (TEM), X-ray diffraction (XRD) analysis and antimicrobial Agar well diffusion methods. The silver nanoparticles showed antibacterial activity against all the pathogenic bacteria; however, this property was lost after treatment of the silver nanoparticles by high temperatures (100 and 300 °C). TEM images showed that the average sizes of heated silver nanoparticles were >100 nm. However, these were <100 nm for non-heated silver nanoparticles. Although, XRD patterns showed the crystalline structure of heated silver nanoparticles, their antibacterial activities were less. This was possible because of the sizes and accordingly less penetration of the particles into the bacterial cells. In addition, elimination of the capping agents by heat might be considered another reason.     

Biosynthesis, characterization and antibacterial activity of silver nanoparticles by aqueous Annona squamosa L. leaf extract at room temperature

Silver nanoparticles (AgNPs) have gained great interest in nanotechnology, biotechnology and medicine. The green synthesis of nanoparticles has received an increasing attention because of it’s maximize efficiency and minimize health and environmental hazards as compared to other conventional chemical synthesis. In this study, we reported biosynthesis of AgNPs by aqueous Annona squamosa L. leaf extract and its characterization by UV-visible spectroscopy (UV–vis), Field emission gun scanning electron microscopy (FEG-SEM), X-ray energy dispersive spectroscopy (EDX), Transmission electron microscopy (TEM), Selected-area electron diffraction (SAED) and Fourier transform infra-red spectroscopy (FTIR). The results indicated that AgNPs formed were spherical in shape with size ranging from 14 to 40 nm with an average diameter 28.47 nm. Furthermore, it was observed that the AgNPs exhibited an antibacterial activity against different Gram positive and Gram negative microorganisms. Our report confirmed that the ALE is a very good eco-friendly and nontoxic bioreductant for the synthesis of AgNPs and opens up further opportunities for fabrication of antibacterial drugs, medical devices and wound dressings.     

Synthesis,characterization, and antibacterial properties of silver nanoparticles-graphene and graphene oxide composites

In the field of nanotechnology, silver nanoparticles have been considered a promising antibacterial material for a century. The potential applications of graphene-based materials are increasingly recognized for their special physico-chemical and biological properties. In particular, graphene and graphene oxide as the foundation of nanocomposites have garnered much interest among researchers in many fields. In this review, we concentrate on different aspects of silver nanoparticle composites with graphene and graphene oxide, focusing on their synthesis methods, special characteristics, and antibacterial properties; we also briefly discuss limitations and future research.