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Buy Copper Nanoparticles [PORTABLE]

In a previous communication, we reported a new method of synthesis of stable metallic copper nanoparticles (Cu-NPs), which had high potency for bacterial cell filamentation and cell killing. The present study deals with the mechanism of filament formation and antibacterial roles of Cu-NPs in E. coli cells. Our results demonstrate that NP-mediated dissipation of cell membrane potential was the probable reason for the formation of cell filaments. On the other hand, Cu-NPs were found to cause multiple toxic effects such as generation of reactive oxygen species, lipid peroxidation, protein oxidation and DNA degradation in E. coli cells. In vitro interaction between plasmid pUC19 DNA and Cu-NPs showed that the degradation of DNA was highly inhibited in the presence of the divalent metal ion chelator EDTA, which indicated a positive role of Cu(2+) ions in the degradation process. Moreover, the fast destabilization, i.e. the reduction in size, of NPs in the presence of EDTA led us to propose that the nascent Cu ions liberated from the NP surface were responsible for higher reactivity of the Cu-NPs than the equivalent amount of its precursor CuCl2; the nascent ions were generated from the oxidation of metallic NPs when they were in the vicinity of agents, namely cells, biomolecules or medium components, to be reduced simultaneously.

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Copper nanoparticles (Cu-NPs) have a wide range of applications as heterogeneous catalysts. In this study, a novel green biosynthesis route for producing Cu-NPs using the metal-reducing bacterium, Shewanella oneidensis is demonstrated. Thin section transmission electron microscopy shows that the Cu-NPs are predominantly intracellular and present in a typical size range of 20-40 nm. Serial block-face scanning electron microscopy demonstrates the Cu-NPs are well-dispersed across the 3D structure of the cells. X-ray absorption near-edge spectroscopy and extended X-ray absorption fine-structure spectroscopy analysis show the nanoparticles are Cu(0), however, atomic resolution images and electron energy loss spectroscopy suggest partial oxidation of the surface layer to Cu2 O upon exposure to air. The catalytic activity of the Cu-NPs is demonstrated in an archetypal "click chemistry" reaction, generating good yields during azide-alkyne cycloadditions, most likely catalyzed by the Cu(I) surface layer of the nanoparticles. Furthermore, cytochrome deletion mutants suggest a novel metal reduction system is involved in enzymatic Cu(II) reduction and Cu-NP synthesis, which is not dependent on the Mtr pathway commonly used to reduce other high oxidation state metals in this bacterium. This work demonstrates a novel, simple, green biosynthesis method for producing efficient copper nanoparticle catalysts.

The average size of the nanoparticle from TEM stayed within a very small range of the average, as indicated by the small error (Table 1). This indicates that the reducing agent provides good control over the average particle size, which is desired in nanoparticle synthesis. Statistical descriptive analysis of particle size of Cu NPs suggests that the statistical skewness (a measure of data asymmetry) was positively skewed. The positive skewness of data indicates an increased number of finer nanoparticles in the distribution. This result agrees with the results obtained by the semiquantitative weight percentage composition of copper species (Table 2).

Zhu et al36 explained the influence of reducing agent ratio on the formation of copper nanoparticles. In this paper, the authors indicate that at low reducing agent ratios, the reduction rate of copper sulphate is slow and only few nuclei of copper can be formed in the early period of the reduction. The atoms formed at that period might participate mainly in collision with already formed nuclei, instead of the formation of new nuclei, so the particle size was larger. As the reducing agent is increased, the percentage of zerovalent copper increases. However at a lower reducing agent ratio, the Cu2O percentage dominates over that of zerovalent copper. During the reduction with lower reducing agent ratio (1.0%), the particles had large size dispersion (49%). Increasing the ratio of ascorbic acid to 1.5% decreased polydispersity significantly to 15.5%. After this ratio, the average particle size and the size dispersion did not change very much.

The off-diagonal peaks are called cross peaks, and indicate that the two bands change at the same time, though not necessarily in the same direction. A positive synchronous cross peak (solid black area) indicates that the variations in intensity at corresponding frequencies proceed in the same direction during the observation period, while a negative synchronous cross peak shows that the changes are in opposite directions. The synchronous plot shows only positive cross peaks, which means that all peak intensities are changing in the same (positive) direction. This plot is in good agreement with the spectroscopic data shown in Figure 8 and substantiates the fact that in the synchronous plot the interaction of copper to carboxylate ion is apparent as the association of copper to oxygen of hydroxyl groups.

Well-diffusion test and dispersed nanoparticles (MIC and MBC) showed high variability in results. Stabilized Cu NPs determined similar zones of inhibition on tested bacteria. The values for diameter of zone of inhibition of the stabilized Cu NPs vary from 9 to 12 mm depending on the bacterial strain; however, it was established that stabilized Cu NPs had antibacterial effects on both Gram-positive and Gram-negative bacteria, showing higher antibacterial activity against E. coli O157: H7 and S. enterica serovar Typhimurium than some of the standard antibiotics.

A copper nanoparticle is a copper based particle 1 to 100 nm in size.[1] Like many other forms of nanoparticles, a copper nanoparticle can be prepared by natural processes or through chemical synthesis.[2] These nanoparticles are of particular interest due to their historical application as coloring agents and the biomedical as well as the antimicrobial ones.[3]

One of the earliest uses of copper nanoparticles was to color glass and ceramics during the ninth century in Mesopotamia.[1] This was done by creating a glaze with copper and silver salts and applying it to clay pottery. When the pottery was baked at high temperatures in reducing conditions, the metal ions migrated to the outer part of the glaze and were reduced to metals.[1] The end result was a double layer of metal nanoparticles with a small amount of glaze in between them. When the finished pottery was exposed to light, the light would penetrate and reflect off the first layer. The light penetrating the first layer would reflect off the second layer of nanoparticles and cause interference effects with light reflecting off the first layer, creating a luster effect that results from both constructive and destructive interference.[2]

Various methods have been described to chemically synthesize copper nanoparticles. An older method involves the reduction of copper hydrazine carboxylate in an aqueous solution using reflux or by heating through ultrasound under an inert argon atmosphere.[4] This results in a combination of copper oxide and pure copper nanoparticle clusters, depending on the method used. A more modern synthesis utilizes copper(II) chloride in a room temperature reaction with sodium citrate or myristic acid in an aqueous solution containing sodium formaldehyde sulfoxylate to obtain a pure copper nanoparticle powder.[5] While these syntheses generate fairly consistent copper nanoparticles, the possibility of controlling the sizes and shapes of copper nanoparticles has also been reported. The reduction of copper(II) acetylacetonate in organic solvent with oleyl amine and oleic acid causes the formation of rod and cube-shaped nanoparticles while variations in reaction temperature affect the size of the synthesized particles.[6]

Another method of synthesis involves using copper (II) hydrazine carboxylate salt with ultrasound or heat in water to generate a radical reaction, as shown in the figure to the right. Copper nanoparticles can also be synthesized using green chemistry to reduce the environmental impact of the reaction. Copper chloride can be reduced using only L-ascorbic acid in a heated aqueous solution to produce stable copper nanoparticles.[7]

Copper nanoparticles display unique characteristics including catalytic and antifungal/antibacterial activities that are not observed in commercial copper. First of all, copper nanoparticles demonstrate a very strong catalytic activity, a property that can be attributed to their large catalytic surface area. With the small size and great porosity, the nanoparticles are able to achieve a higher reaction yield and a shorter reaction time when utilized as reagents in organic and organometallic synthesis.[8] In fact, copper nanoparticles that are used in a condensation reaction of iodobenzene attained about 88% conversion to biphenyl, while the commercial copper exhibited only a conversion of 43%.[8]

Copper nanoparticles that are extremely small and have a high surface to volume ratio can also serve as antifungal/antibacterial agents.[9] The antimicrobial activity is induced by their close interaction with microbial membranes and their metal ions released in solutions.[9] As the nanoparticles oxidize slowly in solutions, cupric ions are released from them and they can create toxic hydroxyl free radicals when the lipid membrane is nearby. Then, the free radicals disassemble lipids in cell membranes through oxidation to degenerate the membranes. As a result, the intracellular substances seep out of cells through the destructed membranes; the cells are no longer able to sustain fundamental biochemical processes.[10] In the end, all these alterations inside of the cell caused by the free radicals lead to cell death.[10]

Copper nanoparticles with great catalytic activities can be applied to biosensors and electrochemical sensors. Redox reactions utilized in those sensors are generally irreversible and also require high overpotentials (more energy) to run. In fact, the nanoparticles have the ability to make the redox reactions reversible and to lower the overpotentials when applied to the sensors.[11] 041b061a72


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