Biogenic synthesis of silver nanoparticles: Antibacterial and cytotoxic potential

In green chemistry, the application of a biogenic material as a mediator in nanoparticles formation is an innovative nanotechnology. Our current investigation aimed at testing the cytotoxic potential and antimicrobial ability of silver nanoparticles (AgNPs) that were prepared using Calligonum comosum roots and Azadirachta indica leaf extracts as stabilizing and reducing agents. An agar well diffusion technique was employed to detect synthesized AgNPs antibacterial ability on Pseudomonas aeruginosa, Escherichia coli, and Staphylococcus aureus bacterial strains. Furthermore, their cytotoxic capability against LoVo, MDA-MB231 and HepG2 ca cells was investigated. For phyto-chemical detection in the biogenic AgNPs the Fourier-transform infrared spectroscopy (FT-IR) was considered. Zeta sizer, TEM (Transmission Electron Microscope) and FE-SEM (Field Emission Scanning Electron Microscope) were used to detect biogenic AgNPs’ size and morphology. The current results showed the capability of tested plant extract for conversion of Ag ions to AgNPs with a mean size ranging between 90.8 ± 0.8 and 183.2 ± 0.7 nm in diameter. Furthermore, prepared AgNPs exhibited apoptotic potential against HepG2, LoVo, and MDA-MB 231cell with IC₅₀ ranging between 10.9 and 21.4 μg/ml and antibacterial ability in the range of 16.0 ± 0.1 to 22.0 ± 1.8 mm diameter. Activation of caspases in AgNPs treated cells could be the main indicator for their positive effect causing apoptosis. The current investigation suggested that the green production of AgNPs could be a suitable substitute to large-scale production of AgNPs, since stable and active nanoparticles could be obtained.     

纳米银的抗菌机制及临床应用研究

纳米银因具备抗菌谱广、效果好、安全性高等特性,其医疗制品在临床治疗方面应用广泛。现普遍认为纳米银可通过释放银离子(Ag+)和诱导活性氧自由基的表达等方式达到杀菌目的,但其发挥抗菌作用的效果受到表面正电荷和粒子直径等因素影响。本文就纳米银的抗菌机制及临床实践应用进行综述,对现有的各种抗菌材料进行分类,重点探讨纳米银对金黄色葡萄球菌、大肠埃希菌、白假丝酵母菌和铜绿假单胞菌的杀菌和抑菌原理,以及其在抗菌过程中的影响因素,并阐述了纳米银及其复合材料在临床实践中的应用,以期为纳米银抗菌应用方面的后续研究提供一些参考。     

Antibacterial and antibiofilm effects of silver nanoparticles against the uropathogen Escherichia coli U12

The drug-resistant bacterial strains' emergence increases day by day. This may be a result of biofilm presence, which protects bacteria from antimicrobial agents. Thus, new approaches must be used to control biofilm-related infections in healthcare settings. In such a study, biological silver nanoparticles were introduced in such a study as an anti-biofilm agent against multidrug-resistant E. coli U12 on urinary catheters. Seven different silver nanoparticles concentrations were tested for their antimicrobial activities. Also, anti-biofilm activities against E. coli U12 were tested. Using the dilution method, the silver nanoparticles concentration of 85 μg/ml was the MIC (Minimum Inhibitory Concentration) that had excellent biocompatibility and showed significant antibacterial activity against E. coli U12. Scanning electron microscopy (SEM) confirmed that the highest efficient dose of silver nanoparticles was 340 μg/ml at 144 h that reduced adhesion of E. coli U12 to the urinary catheter. E. coli U12 cells ruptured cell walls and cell membranes after being examined using transmission electron microscopy (TEM). Thus, biologically prepared silver nanoparticles could be used to coat medical devices since it is effective and promising to inhibit biofilm formation by impregnating urinary catheters with silver nanoparticles.     

Biomedical potential of green synthesized silver nanoparticles from root extract of Asparagus officinalis

Journal of Plant Biochemistry and Biotechnology - Green synthesis of silver nanoparticles (AgNPs) from medicinal plant extracts has gained importance due to its pharmacological potential. In the...     

Transformation of aromatic dyes using green synthesized silver nanoparticles

Nowadays, increasing use of nanoproducts in area of human and environmental applications raises concern about safety aspects of nanoparticles synthesized using traditional physicochemical methods. Silver nanoparticles (AgNPs) synthesis at ambient parameters using latex of medicinally important plant Jatropha gossypifolia (J. gossypifolia) is reported in the present study. Potential of AgNPs in degradation of methylene blue and eosin B was also evaluated. Rapid formation of stable AgNPs was analyzed by visual color change from colorless to yellow-red after addition of latex in AgNO₃ solution and by characteristic surface plasmon resonance (SPR) peak at 430 nm in UV–Vis spectroscopy. FT-IR analysis, protein coagulation test showed capping of proteins, flavonoids, terpenoids and polyphenols of latex on surface of AgNPs. FE-SEM, HR-TEM analysis revealed spherical shape of AgNPs. Narrow size range of AgNPs (5–40 nm) observed in HR-TEM analysis. EDS analysis confirms the presence of elemental silver while XRD revealed crystalline nature of AgNPs. Zeta potential of ?21.4 mV indicates high stability of AgNPs. Effects of different parameters (pH, temperature, incubation time) on nanosynthesis were studied in the present study. Dye reduction studies were performed using UV–Vis spectroscopy, TLC, FT-IR and HPLC analysis showing decreased absorbance maxima of both dyes with respect to time, change in R _f values, changes in wave number, transmittance, and retention time of dyes after AgNPs addition. The rate constant for methylene blue and eosin B reduction by AgNPs was found to be 0.062 and 0.022 min^?1.     

Plasmodium chabaudi-infected mice spleen response to synthesized silver nanoparticles from Indigofera oblongifolia extract

Malaria is a worldwide serious-threatening infectious disease caused by Plasmodium and the parasite resistance to antimalarial drugs has confirmed a significant obstacle to novel therapeutic antimalarial drugs. In this article, we assessed the antioxidant and anti-inflammatory activity of nanoparticles prepared from Indigofera oblongifolia extract (AgNPs) against the infection with Plasmodium chabaudi caused in mice spleen. AgNPs could significantly suppress the parasitaemia caused by the parasite to approximately 98% on day 7 postinfection with P. chabaudi and could improve the histopathological induced spleen damage. Also, AgNPs were able to increase the capsule thickness of the infected mice spleen. In addition, the AgNPs functioned as an antioxidant agent that affects the change in glutathione, nitric oxide and catalase levels in the spleen. Moreover spleen IL1β, IL-6 and TNF-α-mRNA expression was regulated by AgNPs administration to the infected mice. These results indicated the anti-oxidant and the anti-inflammatory protective role of AgNPs against P. chabaudi-induced spleen injury.     

Phytotoxicity of green synthesized silver nanoparticles on Camelina sativa L

Due to the increased production and release of silver nanoparticles (AgNPs) in the environment, the concerns about the possibility of toxicity and oxidative damage to plant ecosystems should be considered. In the present study, the effects of different concentrations of AgNPs (0, 0.5, 1, 2, 3 and 4 g/L) synthesized using the extract of camelina (Camelina sativa) leaves on the growth and the biochemical traits of camelina seedlings were investigated. The results showed that AgNPs significantly increased Ag accumulation in the roots and shoots which decreased the growth and photosynthetic pigments of camelina seedlings. The highest decrease in the height and total dry weight was observed by 53.1 and 61.8% under 4 g/L AgNPs, respectively over control plants. AgNPs application over 2 g/L enhanced the accumulation of proline, malondialdehyde, hydrogen peroxide and methylglyoxal, and up-regulated the activity of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase) and glyoxalase (glyoxalase I and II) system which indicates oxidative stress induction in camelina seedlings. Moreover, AgNPs reduced ASA and GSH contents and increased DHA and GSSG contents, hence disrupting the redox balance. These results showed that AgNPs at 4 g/L had the most toxic effects on the camelina growth. Therefore, increasing oxidative stress markers and the activity of antioxidant enzymes and enzymes involved in glyoxalase system indicated the oxidative stress induced by AgNPs treatments over 2 g/L as well as the induction of antioxidant defense systems to combat AgNPs-induced oxidative stress.     

纳米银的抗菌特性及对多重耐药菌株的抗菌作用

【目的】利用革兰氏阴性细菌、革兰氏阳性细菌和真菌的模式菌株分析纳米银的抗菌特性,并评价纳米银对多重耐药菌株的抗菌作用。【方法】利用生物法合成的纳米银,以微量肉汤法测定3种标准菌株的最小抑菌浓度(MIC)和最小杀菌浓度(MBC),并计算MBC/MIC比值。用系列浓度的纳米银处理3株标准菌株后经平板计数法绘制时间-杀菌曲线。采用菌落平板计数法测定了纳米银对3种标准菌株的"抗生素后效应"(post-antibiotic effect,PAE),最后在生物安全II级实验室测定纳米银对临床分离的多重耐药菌株的抗菌作用。【结果】用生物法合成了粒径5–30 nm的纳米银,zeta电位为–19.5 m V。该纳米银制剂对3种标准菌株的时间-杀菌曲线均表现为时间依赖型抗菌作用。纳米银对大肠杆菌和白色念珠菌"抗生素后效应"随着浓度增加而增加,对金黄色葡萄球菌无明显"抗生素后效应"。纳米银对3种标准菌株的MIC值和MBC值均在1.00–4.00μg/m L之间;对3株人源性多重耐药菌MIC值在6.00–26.00μg/m L之间,MBC值在1.00–32.00μg/m L之间;对14株动物源性多重耐药菌MIC值在4.00–10.00μg/m L之间,MBC值在8.00–16.00μg/m L之间。纳米银对所有测试菌株的MBC/MIC值均小于2。【结论】纳米银是一种时间依赖型的抗菌剂,有不同程度的"抗生素后效应",对人源和动物源性多重耐药菌有杀菌作用。     

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.     

Antibiofilm properties of chemically synthesized silver nanoparticles found against Pseudomonas aeruginosa

Nanomedicine is now being introduced as a recent trend in the field of medicine. It has been documented that metal nanoparticles have antimicrobial effects for bacteria, fungi and viruses. Recent advances in technology has revived the use of silver nanoparticles in the medical field; treatment, diagnosis, monitoring and control of disease. It has been used since ancient times for treating wide range of illnesses. Bacterial cells adheres to surfaces and develop structures known as biofilms. These structures are natural survival strategy of the bacteria to invade the host. They are more tolerant to commonly used antimicrobial agents, thus being more difficult to be controlled. This leads to increase in severity of infection. In this study, we have investigated the effect of silver nanoparticles in the formation of biofilm in multidrug resistant strains of Pseudomonas aeruginosa. Observation showed that biofilm formation occurred at bacterial concentration of 10⁶ cfu/ml for the sensitive strain of P. aeruginosa while in the resistant strain, the biofilm was evident at bacterial concentration of about 10³ cfu/ml. The biofilm were then tested against various concentrations of silver nanoparticles to determine the inhibitory effect of the silver nanoparticles. In the sensitive strain, 20 μg/ml of silver nanoparticles inhibited the growth optimally at bacterial concentration of 10⁴ cfu/ml with an inhibition rate of 67%. Similarly, silver nanoparticles inhibited the formation of biofilm in the resistant strain at an optimal bacterial concentration of 10⁵ cfu/ml with an inhibition rate of 56%. Thus, silver nanoparticles could be used as a potential alternative therapy to reduce severity of disease due to P. aeruginosa infections.     

Catalytic degradation of methylene blue using silver nanoparticles synthesized by honey

This investigation displayed the good catalytic activity of silver nanoparticles (AgNPs) on the reduction of methylene blue dye. During this work, Honey was chosen for environmentally reducing and stabilizing agents for preparation of silver nanoparticles then characterized these nanoparticles by ultraviolet–visible spectroscopy (UV–Vis), functional biomolecules were confirmed by Fourier transform infrared spectroscopy (FTIR). Via transmission electron microscopy (TEM), the size and shape of silver nanoparticles revealed that the particles are spherical and monodispersed without major agglomeration, the particle size ranging from 5 to 25 nm, in addition, the largest particle density levels are 5–10 nm, ZETA Seizers studied the size distribution of the colloidal solution. UV/Vis spectrophotometer and HPLC were used to study and analyze the degradation performance of silver nanoparticles on methylene blue. The results show that 92% of methylene blue has been degraded after 72 h. additionally, several new peaks have appeared after treatment of the samples by using HPLC.     

Characterization of silver nanoparticles synthesized by using marine isolate Streptomyces albidoflavus

Silver nanoparticles production by the green chemistry approach was investigated using an isolated marine actinomycetes strain. The isolated strain was identified as Streptomyces albidoflavus based on chemotaxonomic and ribotyping properties. The strain revealed production of silver nanoparticles both extracellular and intracellularly. Surface Plasmon Resonance analysis with the function of time revealed that particle synthesis by this strain is reaction time dependent. The produced particles were spherical shaped and monodispersive in nature and showed a single surface plasmon resonance peak at 410 nm. Size distribution histograms indicated production of 10-40- nm-size nanoparticles with a mean size of 14.5 nm. FT-IR spectra of nanopartilces showed N-H, C-H, and C-N stretching vibrations, denoting the presence of amino acid/ peptide compounds on the surface of silver nanoparticles produced by S. albidoflavus. Synthesized nanoparticles revealed a mean negative zeta potential and electrophoretic mobility of -8.5 mV and -0.000066 cm2/Vs, respectively. The nanoparticles produced were proteinaceous compounds as capping agents with -8.5 mV zeta potential and revealed antimicrobial activity against both Gram-negative and -positive bacterial strains. Owing to their small size, these particles have greater impact on industrial application spectra.     

Biomedical potential of silver nanoparticles synthesized from calli cells of Citrullus colocynthis (L.) Schrad

Background

Transmission electron microscopy (TEM) remains an important technique to investigate the size, shape and surface characteristics of particles at the nanometer scale. Resulting micrographs are two dimensional projections of objects and their interpretation can be difficult. Recently, electron tomography (ET) is increasingly used to reveal the morphology of nanomaterials (NM) in 3D. In this study, we examined the feasibility to visualize and measure silica and gold NM in suspension using conventional bright field electron tomography.

Results

The general morphology of gold and silica NM was visualized in 3D by conventional TEM in bright field mode. In orthoslices of the examined NM the surface features of a NM could be seen and measured without interference of higher or lower lying structures inherent to conventional TEM. Segmentation by isosurface rendering allowed visualizing the 3D information of an electron tomographic reconstruction in greater detail than digital slicing. From the 3D reconstructions, the surface area and the volume of the examined NM could be estimated directly and the volume-specific surface area (VSSA) was calculated. The mean VSSA of all examined NM was significantly larger than the threshold of 60 m²/cm³. The high correlation between the measured values of area and volume gold nanoparticles with a known spherical morphology and the areas and volumes calculated from the equivalent circle diameter (ECD) of projected nanoparticles (NP) indicates that the values measured from electron tomographic reconstructions are valid for these gold particles.

Conclusion

The characterization and definition of the examined gold and silica NM can benefit from application of conventional bright field electron tomography: the NM can be visualized in 3D, while surface features and the VSSA can be measured.     

Mechanistic aspects of biologically synthesized silver nanoparticles against food- and water-borne microbes

Bioprocess and Biosystems Engineering - In the present study, silver nanoparticles (AgNPs) synthesized from aqueous leaves extract of Malva crispa and their mode of interaction with food- and...     

Chemotactic assay for biological effects of silver nanoparticles

A method is proposed for assessing the biocidal efficacy of water-dispersed nanoparticles of silver. It is based on negative chemotaxis of the plasmodia of the slime mold Physarum polycephalum. Biocidal and repellent effects were compared for silver nanoparticles, Ag⁺ ions, and AOT in solution and in the agar gel. In such characteristics as increasing the period of auto-oscillations of contractile activity, decreasing the area of spreading on substrate, and substrate preference in spatial tests, silver nanoparticles proved to be substantially more effective than Ag⁺ and AOT. The lethal concentrations of the nanoparticles were close to those found earlier for bacteria and viruses. The chemotactic tests allow quantitative assessment of the biological reaction and monitoring its dynamics; in resolution, they are superior to the tests based on the lethal action of biocidal agents.     

Antimicrobial activity of chemically and biologically synthesized silver nanoparticles against some fish pathogens

Pathogens isolated from fish appear to possess considerable antimicrobial resistance and represent a problem for the economy and public health. Natural antimicrobial substitutes to traditional antibiotics represent an essential tool in the fight against antibiotic resistance. Nanotechnology has shown considerable potential in different research fields, and the antimicrobial properties of silver nanoparticles are known. Silver has been used for medical purposes since ancient times because of its bactericidal properties, and the highly reactive surfaces of silver nanoparticles (AgNPs) indicate that they might have a function in antimicrobial applications. This work aimed to study the antimicrobial properties of biologically produced AgNPs from Origanum vulgare leaves compared to chemically produced AgNPs. Both types were characterized by UV–vis spectrophotometry, TEM, and dynamic light scattering and tested against three bacterial strains (Streptococcus agalactiae, and Aeromonas hydrophila, both isolated from Nile tilapia and Vibrio alginolyticus, isolated from sea bass) and three fungal strains (Aspergillus flavus, Fusarium moniliforme, and Candida albicans, all isolated from Nile tilapia). Disk diffusion test and evaluation of ultrastructure changes of tested microorganisms treated with AgNPs by transmission electron microscopy were performed. Moreover, the hemolytic properties of AgNPs were studied on chicken and goat red blood cells. The results obtained declare that the green biological production of silver nanoparticles is safer and more effective than the chemical one; moreover, AgNPs have interesting dose-dependent antimicrobial properties, with better results for biologically produced ones; their effectiveness against tested bacterial and fungal strains opens the way to their use to limit fish diseases, increase economy and improve human health.     

Electrochemical and antibacterial activity of silver nanoparticles synthesized using Mukia madarasapattana leaf extract

In this study, biosynthesis of stable silver nanoparticles (Ag NPs) were prepared using Mukia madarasapattana leaf extract. X-ray diffraction analysis revealed the synthesized silver nanoparticles had face centered cubic crystalline structure. The TEM image showed the silver nanoparticles are not agglomerated, moderately mono dispersed with the size of 15 nm. The high negative zeta potential values indicated the dispersion stability of Ag NPs. Antibacterial activity was carried out against different test microorganisms in silver nanoparticles. The cyclic Voltammetry study showed that Ag NPs have an oxidation peak at 0.61 mV.

     

Antibacterial activity of silver nanoparticles (AgNps) synthesized by tea leaf extracts against pathogenic Vibrio harveyi and its protective efficacy on juvenile Feneropenaeus indicus

Aims: To determine the antibacterial potential of silver nanoparticles (AgNps) synthesized by tea leaf extract against Vibrio harveyi and its protective effect on juvenile Feneropenaeus indicus. Methods and Results: AgNps were synthesized by a simple procedure using tea leaf extract as the reducing agent. Bacteriological tests were performed in Luria–Bertani medium on solid agar plates and in liquid systems supplemented with V. harveyi against different concentrations of AgNps. AgNps synthesized in the present study were shown to be effective against V. harveyi isolated from F. indicus. The combined results of long‐ and short‐term treatment of AgNps synthesized by tea leaf extract showed a 71% reduction in accumulated mortality. Conclusions: The long‐term administration of AgNps synthesized by tea leaf extracts at the concentration of 10 μg significantly reduced the mortalities in F. indicus from V. harveyi infections. Significance and Impact of the Study: The AgNps synthesized by tea leaf extract may be an alternative to antibiotics in controlling V. harveyi infections.