Nanoparticle

Silver nanoparticles (Ag NPs) play important roles in the development of plasmonic applications. Combining these nanoparticles with graphene can yield hybrid materials with enhanced light–matter interaction. Here, we report a simple method for the synthesis of graphene–silver nanoparticle hybrids on highly oriented pyrolytic graphite (HOPG) substrates. We demonstrate by scanning tunneling microscopy and local tunneling spectroscopy measurements the electrostatic n-type doping of graphene by contact with silver. We show by UV-Vis reflectance investigations that the local surface plasmon resonance (LSPR) of Ag NPs partially covered with graphene is preserved for at least three months, i.e., three times longer than the LSPR of bare Ag NPs. The gradual loss of LSPR is due to the spontaneous sulfurization of non-covered Ag NPs, as revealed by scanning electron microscopy and energy-dispersive X-ray spectroscopy. We show that the Ag NPs completely sandwiched between graphene and HOPG do n...

Amphiphilic gold nanoclusters with the diameter of 1.8 ± 0.2 nm were prepared by decomposition of organometallic gold precursor CH3AuPPh3 in the presence of mercaptoacids in o-xylene. Self-assembly of the 16-mercaptohexadecanoic acid protected gold clusters led to the formation of the nanosheets consisted of aligned gold clusters. The hydrogen bonding between the carboxylic groups attached on the adjacent gold clusters likely drives the self-assembly. This phenomenon was cross-verified by employing the preheated mercaptoacid-amine surfactant system where a part of the mercaptoacids and amines were converted into –NH3+–−OOC– ion pair and interrupting a part of the hydrogen bonding sites to lead to the reduction in the size of the structures from nanosheets to nanobelts. Interestingly, we found the dependency of the luminescent properties on the extent of maintaining the self-assembly of the clusters intern dictated by the surfactants.

An eco-friendly microbial method for synthesis of silver colloid solution with antimicrobial activity is developed using a fungal strain of Peni-cillium purpurogenum NPMF. It is observed that increase in concentration of AgNO3 increases the formation of silver nanoparticle. At ...

Solubilization of hydrophobic drugs at the molecular level as inclusion complexes inside cyclodextrins (CDs) offers a good alternative for improving their stability, solubility and bioavailability, and for preventing against their possible toxicity or controlling secondary effects. Therefore CDs are widely used as solubilizing excipients. However since dissociation takes place too readily upon dilution, inclusion complexes inside simple water-soluble CD appears ineffective for drug delivery applications. Chemical modifications of CDs allow them to self-organize as larger assemblies useful for resolving this lability issue. Depending on the position, the number and the nature of these groups, amphiphilic CDs can form assemblies such as vesicles, solid-lipid nanoparticles, nanospheres, liquid crystals, or micellar systems. This review deals with the synthesis of amphiphilic cyclodextrins leading to supramolecular assemblies and the physical properties of these assemblies. From the fir...

The potential eco-toxicity of nanosized titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) water suspensions was investigated using Gram-positive Bacillus subtilis and Gram-negative Escherichia coli as test organisms. These three photosensitive nanomaterials were harmful to varying degrees, with antibacterial activity increasing with particle concentration. Antibacterial activity generally increased from SiO2 to TiO2 to ZnO, and B. subtilis was most susceptible to their effects. Advertised nanoparticle size did not correspond to true particle size. Apparently, aggregation produced similarly sized particles that had similar antibacterial activity at a given concentration. The presence of light was a significant factor under most conditions tested, presumably due to its role in promoting generation of reactive oxygen species (ROS). However, bacterial growth inhibition was also observed under dark conditions, indicating that undetermined mechanisms additional to photocatalytic ROS production were responsible for toxicity. These results highlight the need for caution during the use and disposal of such manufactured nanomaterials to prevent unintended environmental impacts, as well as the importance of further research on the mechanisms and factors that increase toxicity to enhance risk management.

The efficiency of Zinc Oxide nanoparticles on removal of E124 dye in aqueous solution has been studied. Different factors and parameters that affect the degradation efficiency of E124 dye were studied including the initial concentration of pollutant, pH of solution, treatment time, concentration of ZnO nanoparticle (ZnO NP), temperature and salt addition. Under the achieved optimal conditions (initial concentration of dye solution 5ppm, treatment time 80 min, concentration of ZnO NP 0.08g, pH 7 and temperature of 40 0C) for best removal of E124 dye from aqueous solution the efficiency of ZnO NP doped with Ag+ was tested. Different amounts of Ag+ % doped on ZnO NP from 0.5 to 2% were tested and the highest dye removal % of 92 was achieved at 1 % Ag+ doping of ZnO NP.

Physico-chemical investigation on adsorption of congo red, an anionic azo dye by chitosan hydrobeads has been carried out. Adsorption process has been found to be dependant on temperature with optimum activity at 30 °C. Both ionic interaction as well as physical forces is responsible for binding of congo red with chitosan. Theoretical correlation of the experimental equilibrium adsorption data for congo red–chitosan hydrobeads system would be best explained by linearized form of Langmuir isotherm model. The kinetic results follow pseudo second-order rate equation. pH of the experimental solution influenced congo red adsorption inversely, and ∼20.0% of the dye could be desorbed from the loaded beads by changing the pH of the solution to alkaline range (∼pH 12.0). Both sodium chloride and sodium dodecyl sulfate significantly influenced the adsorption process.

Enabled by their size and supramolecular structures, nanoparticles (that is, particles of approximately 10 to 100 nanometers) promise to be particularly capable agents in the detection, diagnosis, and treatment of cancer. When loaded with chemotherapeutic agents, nanoparticle delivery to cancerous tissues relative to healthy tissues may be favorably biased by size and through the attachment of targeting ligands to the surface of the particle. Nanoparticles may be made from a variety of materials, and in addition to chemotherapeutic payloads, nanoparticles can incorporate non-bioactive elements useful as diagnostic and device agents. For example, the inclusion of iron oxide colloids enables nanoparticle use as magnetic resonance imaging (MRI) contrast agents, and also, through the application of an alternating magnetic field (AMF), enables the particle to generate enough heat to be used for hyperthermic therapeutic applications. In this report, we also introduce novel Magnetic Nanoparticle Hydro-Gel (MagNaGelTM) materials comprised of chemotherapeutic agents, iron oxide colloids, and targeting ligands. MagNaGel particles were fabricated in the 20- to 40-nm size range with very narrow size dispersion. These particles demonstrate high (>10 wt %) chemotherapeutic loading, tumor-associated biomolecular binding, good magnetic susceptibility, and attractive toxicity and circulation profiles in mouse models. Looking forward, the convergence of drug and device on the nano-scale promises treatment modalities that cannot be practiced through traditionally distinct drug and device combinations. MagNaGel nanoparticles are drug-device hybrids that, when used in conjunction with diagnostic MRI and inductive heating, may play a key role in new and powerful cancer treatment regimens. Drug Dev. Res. 67:70–93, 2006. © 2006 Wiley-Liss, Inc.

Cyclic voltammetry of the CuCl powder in a cavity microelectrode revealed direct electro-reduction in solid state in 1-butyl-3-methylimidazolium hexafluorophosphate. Potentiostatic electrolysis of the salt powder (attached to a current collector) in the ionic liquid produced Cu ...

Protein kinase CK2, a protein serine/threonine kinase, plays a global role in activities related to cell growth, cell death, and cell survival. CK2 has a large number of potential substrates localized in diverse locations in the cell including, for example, NF-κB as an important downstream target of the kinase. In addition to its involvement in cell growth and proliferation it is also a potent suppressor of apoptosis, raising its key importance in cancer cell phenotype. CK2 interacts with diverse pathways which illustrates the breadth of its impact on the cellular machinery of both cell growth and cell death giving it the status of a “master regulator” in the cell. With respect to cancer, CK2 has been found to be dysregulated in all cancers examined demonstrating increased protein expression levels and nuclear localization in cancer cells compared with their normal counterparts. We originally proposed CK2 as a potentially important target for cancer therapy. Given the ubiquitous and essential for cell survival nature of the kinase, an important consideration would be to target it specifically in cancer cells while sparing normal cells. Towards that end, our design of a tenascin based sub-50 nm (i.e., less than 50 nm size) nanocapsule in which an anti-CK2 therapeutic agent can be packaged is highly promising because this formulation can specifically deliver the cargo intracellularly to the cancer cells in vivo. Thus, appropriate strategies to target CK2 especially by molecular approaches may lead to a highly feasible and effective approach to eradication of a given cancer.