Copper-based Nanoparticles Research Articles

Toxic effects of copper-based nanoparticles or compounds to lettuce (Lactuca sativa) and alfalfa (Medicago sativa).

The increased production and use of nanoparticles (NPs) has generated concerns about their impact on living organisms. In this study, nCu, bulk Cu, nCuO, bulk CuO, Cu(OH)2 (CuPRO 2005, Kocide 3000), and CuCl2 were exposed for 15 days to 10 days-old hydroponically grown lettuce (Lactuca sativa) and alfalfa (Medicago sativa). Each compound was applied at 0, 5, 10, and 20 mg L(-1). At harvest, we measured the size of the plants and determined the concentration of Cu, macro and microelements by using ICP-OES. Catalase and ascorbate peroxidase activity was also determined. Results showed that all Cu NPs/compounds reduced the root length by 49% in both plant species. All Cu NPs/compounds increased Cu, P, and S (>100%, >50%, and >20%, respectively) in alfalfa shoots and decreased P and Fe in lettuce shoot (>50% and >50%, respectively, excluding Fe in CuCl2 treatment). Biochemical assays showed reduced catalase activity in alfalfa (root and shoot) and increased ascorbate peroxidase activity in roots of both plant species. Results suggest that Cu NPs/compounds not only reduced the size of the plants but altered nutrient content and enzyme activity in both plant species.

Matching the organic and inorganic counterparts during nucleation and growth of copper-based nanoparticles – in situ spectroscopic studies

Closing the loop: initially, the reactivity of benzyl alcohol determines the nucleation of Cu nanoparticles, but as soon as they start to form they begin to catalyze the condensation of benzyl alcohol to dibenzylether.

Influence of extracellular polymeric substances on the long-term fate, dissolution, and speciation of copper-based nanoparticles.

The influence of phytoplankton-derived soluble extracellular polymeric substances (EPS), pH, and ionic strength (IS) on the dissolution, speciation, and stability of nano-CuO, nano-Cu, and Kocide (a micron sized Cu(OH)2-based fungicide) was investigated over 90 days. EPS improved the stability of commercial copper-based nanoparticles (CBNPs) in most conditions, in addition to influencing their dissolution. The dissolution rate was pH 4≫pH 7>pH 11. The presence of EPS correlated with higher dissolved Cu at pH 7 and 11, and lower dissolved Cu at pH 4. More dissolution was observed at higher IS (NaCl) due to complexation with Cl-. Dissolution of nano-CuO at pH 7 increased from 0.93% after 90 days (without EPS) to 2.01% (with 5 mg-C EPS/L) at 10 mM IS. Nano-CuO dissolved even more (2.42%) when IS was increased to 100 mM NaCl (with EPS). The ratio of free-Cu2+/total dissolved Cu decreased in the presence of EPS, or as pH and/or IS increased. On a Cu mass basis, Kocide had the highest dissolved and suspended Cu at pH 7. However, dissolution of nano-Cu resulted in a higher fraction of free Cu2+, which may make nano-Cu more toxic to pelagic organisms.

Bioactivity, mechanism of action, and cytotoxicity of copper-based nanoparticles: A review

Nanotechnology is an emerging branch of science, which has potential to solve many problems in different fields. The union of nanotechnology with other fields of sciences including physics, chemistry, and biology has brought the concept of synthesis of nanoparticles from their respective metals. Till date, many types of nanoparticles have been synthesized and being used in different fields for various applications. Moreover, copper nanoparticles attract biologists because of their significant and broad-spectrum bioactivity. Due to the large surface area to volume ratio, copper nanoparticles have been used as potential antimicrobial agent in many biomedical applications. But the excess use of any metal nanoparticles increase the chance of toxicity to humans, other living beings, and environment. In this article, we have critically reviewed the bioactivities and cytotoxicity of copper nanoparticles. We have also focused on possible mechanism involved in its interaction with microbes.

Molecular Responses of Mouse Macrophages to Copper and Copper Oxide Nanoparticles Inferred from Proteomic Analyses

The molecular responses of macrophages to copper-based nanoparticles have been investigated via a combination of proteomic and biochemical approaches, using the RAW264.7 cell line as a model. Both metallic copper and copper oxide nanoparticles have been tested, with copper ion and zirconium oxide nanoparticles used as controls. Proteomic analysis highlighted changes in proteins implicated in oxidative stress responses (superoxide dismutases and peroxiredoxins), glutathione biosynthesis, the actomyosin cytoskeleton, and mitochondrial proteins (especially oxidative phosphorylation complex subunits). Validation studies employing functional analyses showed that the increases in glutathione biosynthesis and in mitochondrial complexes observed in the proteomic screen were critical to cell survival upon stress with copper-based nanoparticles; pharmacological inhibition of these two pathways enhanced cell vulnerability to copper-based nanoparticles, but not to copper ions. Furthermore, functional analyses using primary macrophages derived from bone marrow showed a decrease in reduced glutathione levels, a decrease in the mitochondrial transmembrane potential, and inhibition of phagocytosis and of lipopolysaccharide-induced nitric oxide production. However, only a fraction of these effects could be obtained with copper ions. In conclusion, this study showed that macrophage functions are significantly altered by copper-based nanoparticles. Also highlighted are the cellular pathways modulated by cells for survival and the exemplified cross-toxicities that can occur between copper-based nanoparticles and pharmacological agents.

Biological and Environmental Transformations of Copper-Based Nanomaterials

Copper-based nanoparticles are an important class of materials with applications as catalysts, conductive inks, and antimicrobial agents. Environmental and safety issues are particularly important for copper-based nanomaterials because of their potential large-scale use and their high redox activity and toxicity reported from in vitro studies. Elemental nanocopper oxidizes readily upon atmospheric exposure during storage and use, so copper oxides are highly relevant phases to consider in studies of environmental and health impacts. Here we show that copper oxide nanoparticles undergo profound chemical transformations under conditions relevant to living systems and the natural environment. Copper oxide nanoparticle (CuO-NP) dissolution occurs at lysosomal pH (4-5), but not at neutral pH in pure water. Despite the near-neutral pH of cell culture medium, CuO-NPs undergo significant dissolution in media over time scales relevant to toxicity testing because of ligand-assisted ion release, in which amino acid complexation is an important contributor. Electron paramagnetic resonance (EPR) spectroscopy shows that dissolved copper in association with CuO-NPs are the primary redox-active species. CuO-NPs also undergo sulfidation by a dissolution-reprecipitation mechanism, and the new sulfide surfaces act as catalysts for sulfide oxidation. Copper sulfide NPs are found to be much less cytotoxic than CuO-NPs, which is consistent with the very low solubility of CuS. Despite this low solubility of CuS, EPR studies show that sulfidated CuO continues to generate some ROS activity due to the release of free copper by H2O2 oxidation during the Fenton-chemistry-based EPR assay. While sulfidation can serve as a natural detoxification process for nanosilver and other chalcophile metals, our results suggest that sulfidation may not fully and permanently detoxify copper in biological or environmental compartments that contain reactive oxygen species.

Analytical characterization and antimicrobial properties of novel copper nanoparticle–loaded electrosynthesized hydrogel coatings

In this study, a novel antimicrobial coating was developed to avoid infections and to provide sterile conditions for stainless steel devices. Poly(ethylene glycol diacrylate) hydrogel thin films were modified with copper-based nanoparticles, following two different entrapment procedures. These coatings were firmly attached on metal substrates by means of a simple and fast electrochemical polymerization technique. The surface composition of the Cu nanoparticles–modified hydrogel coatings and their bactericidal effect against Staphylococcus aureus and Escherichia coli was studied, and the efficacy of such systems in preventing bacterial infections demonstrated.

Evaluation of copper iodide and copper phosphate nanoparticles for their potential cytotoxic effect

To explore the potential biological activities of transition metal-based nanoparticles (NPs), we synthesized two copper-based NPs, CuI and Cu3(PO4)2. The structural features of these NPs were determined by the X-ray diffraction (XRD), dynamic light scattering (DLS) and transmission electron microscopy (TEM). The size of CuI and Cu3(PO4)2 NPs were 35 ± 4.2 nm and 67 ± 6.3 nm respectively as determined by TEM. Cell viability, generation of reactive oxygen species (ROS), cell cycle and induction of apoptosis were assessed on human breast cancer cell line MCF7 after the treatment of these NPs. Exposure of CuI and Cu3(PO4)2 NPs decreased cell viability in a dose-dependent manner. Also, CuI NPs produced more ROS compared to Cu3(PO4)2 and presence of N-acetyl cysteine (NAC) along with NPs increased the cell survival. Cell cycle analysis indicated that after exposure of these NPs at their respective LD50 doses increased Sub G1 and G2/M peak after 8 h and 24 h of treatment respectively. Apoptosis study by AnnexinV-FITC staining showed slight increased in the early and late apoptosis after 8 h of treatment and most of the cells were dead after 24 h of treatment. Thus our observations suggest that the exposure of these two NPs induced dose-dependent cytotoxicity on MCF7 cell that is associated with ROS-mediated apoptosis.

Novel Porous Composite Material Containing Catalytic Nanoparticles for Hydrogen Production from Biofuel

ABSTRACTIn this study, a novel flow-based method is presented to place catalytic nanoparticles into a reactor by sol-gelation of a porous ceramic consisting of copper-based nanoparticles, silica sand, ceramic binder, and a gelation agent. This method allows for the placement of a liquid precursor containing the catalyst into the final reactor geometry without the need of impregnating or coating of a substrate with the catalytic material. The so generated foam-like porous ceramic shows properties highly appropriate for use as catalytic reactor material, e.g., reasonable pressure drop due to its porosity, high thermal and catalytic stability, and excellent catalytic behavior.The catalytic activity of micro-reactors containing this foam-like ceramic is tested in terms of their ability to convert alcoholic biofuel (e.g. methanol) to a hydrogen-rich gas mixture with low concentrations of carbon monoxide (up to 75% hydrogen content and less than 0.2% CO, for the case of methanol). This gas mixture is subsequently used in a low-temperature fuel cell, converting the hydrogen directly to electricity. A low concentration of CO is crucial to avoid poisoning of the fuel cell catalyst. Since conventional Polymer Electrolyte Membrane (PEM) fuel cells require CO concentrations far below 100 ppm and since most methods to reduce the mole fraction of CO (such as Preferential Oxidation or PROX) have CO conversions of up to 99%, the alcohol fuel reformer has to achieve initial CO mole fractions significantly below 1%. The catalyst and the porous ceramic reactor of the present study can successfully fulfill this requirement.The results of the present study confirm that product gas mixtures with up to 75% hydrogen content and less than 0.2% CO content can be achieved, which is an excellent result. The reactor temperature can be kept as low as 220°C while obtaining a methanol conversion of up to 70%. The used PROX catalyst showed selective CO conversion rates above 99.5% for temperatures between 80 and 100°C in presence of large molar fractions of H2O and CO2.

Formation of paratacamite nanomaterials via the conversion of aged and oxidized copper nanoparticles in hydrochloric acidic media

Nanoparticles and nanostructured aggregates of paratacamite are prepared in acidic solutions through the conversion of copper-based nanoparticles. Aged and oxidized copper nanoparticles with an average primary particle size of ∼15 nm, when combined with hydrochloric acid solutions in the range of 0.025 to 0.1 M, show interesting behavior yielding both a change in nanoparticle primary size, as measured by an electrospray scanning mobility particle sizer, and in chemical composition to produce a copper chloride hydroxide mineral identified as paratacamite (γ-Cu2(OH)3Cl) by powder X-ray diffraction of the dehydrated solid sample. Taken together, these data suggest that paratacamite nanoparticles in solution can aggregate to yield microporous paratacamite materials. Microporous paratacamite was characterized by several techniques including X-ray diffraction, transmission electron microscopy, energy dispersive X-ray analysis, electron energy loss spectroscopy, X-ray photoelectron spectroscopy and surface area measurements. Oxidation of these copper-based nanoparticles with molecular oxygen and the role of the oxidized layer in the formation of paratacamite have been investigated. Comparison to microscale copper particles showed there is unique oxidation behavior of nanoscale copper particles that results in unique reaction chemistry of oxidized nanoscale copper particles with hydrochloric acid solutions to form paratacamite. This study provides a new route for the formation of paratacamite nanomaterials that can be used in a wide range of chemically interesting applications including hydrogen storage materials and as a heterogeneous catalyst for the synthesis of green solvents such as dimethyl and diethyl carbonates. Additionally, this study suggests a potentially new pathway for the degradation of art objects and ancient artifacts as well as other cultural heritage materials containing small copper particles that has not been previously considered.

ChemInform Abstract: PEG3400—Cu2O—Cs2CO3: An Efficient and Recyclable Microwave‐Enhanced Catalytic System for Ligand‐Free Ullmann Arylation of Indole and Benzimidazole.

Abstract A mild, simple and efficient microwave-enhanced copper-catalyzed protocol for N-arylation using high molecular weight poly(ethylene glycol) (PEG3400) as a solvent is reported. Indole and benzimidazole have been N-arylated in the presence of cuprous oxide, cesium carbonate, and PEG3400, under microwave activation, with no supplementary ligands. Simple treatment by precipitation in Et2O and filtration provided the expected product after evaporation and recovery of the catalytic system as a precipitate. The recovery and one successful re-use of the catalytic system is also described. The formation of copper-based nanoparticles was demonstrated by TEM analysis.

Cu and CuO nanoparticles immobilized by silica thin films as antibacterial materials and photocatalysts

Abstract CuO nanoparticles with average diameter of about 20 nm were accumulated on surface of sol–gel silica thin films heat treated at 300 °C in air. Heat treatment of the CuO nanoparticles at 600 °C in a reducing environment resulted in effective reduction of the nanoparticles and penetration of them into the film. While the thin films heat treated at 300 °C exhibited a strong antibacterial activity against Escherichia coli bacteria, the reducing process decreased their antibacterial activity. However, by definition of normalized antibacterial activity (antibacterial activity/surface concentration of coppers) it was found that Cu nanoparticles were more toxic to the bacteria than the CuO nanoparticles (by a factor of ∼ 2.1). Thus, the lower antibacterial activity of the reduced thin films was assigned to diffusion of the initially accumulated copper-based nanoparticles into the film. The CuO nanoparticles also exhibited a slight photocatalytic activity for inactivation of the bacteria (∼ 22% improvement in their antibacterial activity). Instead, the normalized antibacterial activity of the Cu nanoparticles covered by a thin oxide layer highly increased (∼ 63% improvement) in the photocatalytic process. A mechanism was also proposed to describe the better antibacterial activity of the Cu than CuO nanoparticles in dark and under light irradiation.

PEG 3400–Cu 2O–Cs 2CO 3: an efficient and recyclable microwave-enhanced catalytic system for ligand-free Ullmann arylation of indole and benzimidazole

A mild, simple and efficient microwave-enhanced copper-catalyzed protocol for N-arylation using high molecular weight poly(ethylene glycol) (PEG 3400) as a solvent is reported. Indole and benzimidazole have been N-arylated in the presence of cuprous oxide, cesium carbonate, and PEG 3400, under microwave activation, with no supplementary ligands. Simple treatment by precipitation in Et 2O and filtration provided the expected product after evaporation and recovery of the catalytic system as a precipitate. The recovery and one successful re-use of the catalytic system is also described. The formation of copper-based nanoparticles was demonstrated by TEM analysis.

Formation and dissolution of copper-based nanoparticles in SiO 2 sol–gel film using heat treatment and/or UV light exposure

We report in this paper, results on the formation and dissolution of Cu-based nanoparticles in sol–gel SiO 2 thin films using heat treatment and UV light exposure, respectively. Using UV–vis-NIR spectroscopy, we have shown that Cu 2O nanoparticles can be generated by controlling the aging of the sol prior to film deposition while the Cu 0 nanoparticles can be synthesized using a heat treatment in H 2 atmosphere at 550 °C for 6 h. It has been also demonstrated that irradiation with an UV pulsed (Q-switched Nd:YAG) or continuous black ray UV lamp can dissolve these Cu-based nanoparticles with controlled, spatial selectivity. The mechanism of the dissolution process was found to be mainly thermal. Finally, we report a new analytical technique for detecting/confirming the presence of low densities of Cu nanoparticles in the films, based on a relative heat flow measurement of such films using a micro-thermal analyzer (e.g., TA Instruments μTA model 2990).