Biogenic synthesis of silver nanoparticles using ginger(Zingiber officinale)extract and their antibacterial properties against aquatic pathogens

With the development of aquaculture, there is an urgent demand for an alternative antibacterial agent to reduce the drug resistance and environmental pollution caused by the abuse of antibiotics. Recently, silver nanoparticles（Ag NPs） have been viewed as a novel type of antimicrobial agents due to their unique advantages. In this study,Ag NPs were biosynthesized with the ginger rhizomes extract. The biosynthesized Ag NPs were characterised by UV–visible spectroscopy, transmission electron microscopy, X-ray diffraction and fourier transform infrared spectroscopy. Furthermore, the antimicrobial activities of the Ag NPs were fully analyzed against six typical aquatic pathogens. The results indicated that the components in ginger extract could function as the chemical reductant to synthesize Ag NPs. Moreover, compared with the Ag NPs synthesized by chemical methods, the biosynthesized Ag NPs were smaller, and had higher stability and antibacterial activity. Therefore, the biosynthesized Ag NPs using ginger extract may have prospective applications in aquaculture.

Spectral features and antibacterial properties of Cu-doped ZnO nanoparticles prepared by sol-gel method

Zn（1-x）Cux O（x=0.00, 0.01, 0.03, and 0.05） nanoparticles are synthesized via the sol-gel technique using gelatin and nitrate precursors. The impact of copper concentration on the structural, optical, and antibacterial properties of these nanoparticles is demonstrated. Powder x-ray diffraction investigations have illustrated the organized Cu doping into ZnO nanoparticles up to Cu concentration of 5%（x = 0.05）. However, the peak corresponding to CuO for x= 0.01 is not distinguishable. The images of field emission scanning electron microscopy demonstrate the existence of a nearly spherical shape with a size in the range of 30–52 nm. Doping Cu creates the Cu–O–Zn on the surface and results in a decrease in the crystallite size. Photoluminescence and absorption spectra display that doping Cu causes an increment in the energy band gap. The antibacterial activities of the nanoparticles are examined against Escherichia coli（Gram negative bacteria）cultures using optical density at 600 nm and a comparison of the size of inhibition zone diameter. It is found that both pure and doped ZnO nanoparticles indicate appropriate antibacterial activity which rises with Cu doping.

Antibacterial properties of copper-substituted cobalt ferrite nanoparticles synthesized by co-precipitation method

Controlled growth and careful characterization of cobalt ferrite nanoparticles for antibacterial applica- tions are challenging. Copper-substituted cobalt ferrite nanoparticles （CuxCo1-xFe2O4）, where x = 0.0, 0.3, 0.5, 0.7 and 1.0, were synthesized using an economical and simple co-precipitation technique. The crys- tal structure and antibacterial properties of the samples as a function of Cu-substituted content were systematically studied. With increasing Cu concentration, the nanopartide size decreased from ~30 to ~20 nm. The Fourier transform infra-red spectra exhibit two prominent fundamental absorption bands, at ~595 and 419 cm^-1. These bands correspond to intrinsic stretching vibrations of metals at tetrahedral and octahedral sites, respectively. The Raman scattering results reveal that increasing the Cu content enhances the local disorder at both tetrahedral and octahedral sub lattices. The results indicate that the substitution of Co with Cu in cobalt ferrite nanoparticles strongly influences the microstructure, crystal structure, and oarticle diameter, and also improves the antibacterial properties.

Antibacterial and Antioxidant Activities of ZnO Nanoparticles Synthesized Using Extracts of Allium sativum,Rosmarinus officinalis and Ocimum basilicum

ZnO nanoparticles（ZnO NPs） were synthesized by chemical method（coprecipitation） and biological method using aqueous extracts of garlic（Allium sativum）,rosemary（Rosmarinus officinalis） and basil（Ocimum basilicum）.The influence of plant extract on the antibacterial and antioxidant activities of green synthesized nanoparticles was investigated.The X-ray diffraction studies reveal that all ZnO samples have hexagonal wurtzite structure.The particle size of ZnO NPs estimated by transmission electron microscopy analysis（between 14 and 27 nm） varies depending on the synthesis method of nanoparticles and the type of extracts from the plants used.The functional groups involved in the biosynthetic procedure were evidenced by Fourier transform infrared spectroscopy.The presence of Mn^（2＋）ions,Zn vacancy complexes and oxygen vacancies in ZnO samples was highlighted by electron paramagnetic resonance spectroscopy.The green synthesized ZnO NPs have shown a good bactericidal activity against Staphylococcus aureus,Bacillus subtilis,Listeria monocytogenes,Escherichia coli,Salmonella typhimurium and Pseudomonas aeruginosa bacterial strains.ZnO NPs synthesized using extracts of the selected plant species have been found to exhibit more enhanced antibacterial and antioxidant activities as compared to chemical ZnO NPs.

Synergistic Effect of Metal Nanoparticles on the Antimicrobial Activities of Antibiotics against Biorecycling Microbes

Biorecycling microbes, which have critical functionalities in natural cycles, are essential to sustain eco-system of the earth. Any alterations in these cycles caused by the mutations of microbes could be a potential threat to life on earth. Antibiotics leached from pharmaceutical waste, animal food and agribusiness prod- ucts are accumulating in the environment. Metal nanoparticles are also accumulating in environment because of their extensive use as biocidal agent in domestic products. Interaction of antibiotics and metal nanoparticles with eco-ffiendly microorganisms has a potential to alter the ecosystem of the earth. In this article, we have studied the antibacterial activities of silver and copper nanoparticles and their for- mulations with antibiotics, tetracycline, and kanamycin against biorecycling microbes, Bacillus subtilis and Pseudomonas fluorescens. Strong synergistic effect of metal nanoparticles on the antimicrobial ac- tivities of commercial antibiotics has been observed. Antimicrobial activity of tetracycline improves by 286%-346% and 0%-28% when being tested in the presence of 250 ppm of silver and copper nanoparticles, respectively. For kanamycin, the improvement is 154%-289% for silver and 3%-20% for copper nanoparticles. Irrespective of the antibiotics and tested organisms, synergy is more prominent for silver nanoparticles even at their minimum active concentration （100 ppm）. This study demonstrates that the combination of metal nanoparticles with antibiotics could be more fatal to ecosystem than either the metal nanoparticles or the antibiotics alone.

Green-synthesized gold nanoparticles from Plumeria alba flower extract to augment catalytic degradation of organic dyes and inhibit bacterial growth

Bio-inspired eco-friendly gold nanoparticles were synthesized by a green method using aqueous Plume- ria alba flower extract （PAFE）. The use of 1% and 5% concentrations of PAFE resulted in two different sizes of P. alba gold nanoparticles, PAGNPsl and PAGNPs2, with surface plasmon resonance （SPR） peaks at 552 and 536 nm, respectively. Size-controlled formation of gold nanoparticles was indicated by the SPR shift observed with increasing concentration of PAFE. The accurate size and morphology of PAGNPs I and PAGNPs2 were determined by transmission electron microscope （TEM） analysis is found to be 28 ＋ 5.6 and 15.6 4-3.4 nm, respectively, and those are spherical in shape. The antibacterial activity of PAGNPsl and PAGNPs2 was tested against Escherichia coil; the small-sized PAGNPs2 exhibited better antibacterial activity with a 16-mm zone of inhibition at a concentration of 400 txg/mL. Furthermore, the catalytic activity of PAGNPsl and PAGNPs2 was analyzed on six hazardous dyes; PAGNPs2 exhibited more pro- nounced catalytic activity than PAGNPsl. Among all of the dyes, 4-nitrophenol was most rapidly degraded to 4-aminophenol by PAGNPs2 within 5 min. The mechanism of catalysis in the presence of PAGNPsl and PAGNPs2 can be described as an electron transfer process from donor NaBH4 to an acceptor. The facile green synthesis of such eco-friendly nanoparticles in bulk suggests this method has potential industrial applications.

Synthesis of Ag/AgCl-mesoporous silica nanocomposites using a simple aqueous solution-based chemical method and a study of their antibacterial activity on E. coli

Simple aqueous solution-based chemical methods have been developed for the synthesis of Ag/AgCI nanoparticle-mesoporous silica nanocomposites. Ag loading in the mesoporous silica was accomplished using a wet-impregnation method. The AgCl-mesoporous silica nanocomposite material （AgCl-mSi） was synthesized by using a ＇one pot method. Synthesized materials were characterized using X-ray diffraction, N2 adsorption-desorption analysis and high-resolution transmission electron microscopy. Antibacterial activity of the synthesized materials was investigated against Escherichia coil （E. coil） using the conventional plate-count method. All the materials showed high antibacterial activity even when the percentage loading of Ag in the nanocomposite was as low as 10wt%.

Novel synthesis and characterization of CuO nanomaterials:Biological applications

CuO nanoparticles were synthesized at a relatively low temperature（80 ℃） for 2 h using polyethylene glycol-glycerol mixture which acts as a capping agent.A detailed characterization of the synthesized nanomaterials were performed utilizing X-ray diffraction（XRD）,infra-red spectroscopy（IR）,thermogravimetric analysis（TGA-DTA）,transmission electron microscopy（TEM）,photoluminescence（PL） by studying its crystalline phase,vibrational mode,thermal analysis,morphology and photoluminescence properties.The effect of annealing on the as-prepared nanoparticles were studied and compared with their corresponding bulk counterpart.The synthesized nanoparticles have been screened for in vitro cytotoxicity（1C_（50）） studies against the human cervical adenocarcinoma cell line（HeLa） using WITT assay methods.The as-prepared nanoparticle inhibits the proliferation of this HeLa cell.The standard disc diffusion method has been used to study the antibacterial activity of the samples against the human pathogenic bacteria Escherichia coli（MTCC 729）,Proteus mirabilis（MTCC 425） and Klebsiella pneumoniae subsp.pneumoniae（MTCC 432）.The results have been compared with the positive control antibiotic gentamycin.The synthesized nanoparticles would provide a potential alternative to antibiotics for controlling some of the microorganisms causing urolithiasis.