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Green Synthesis of Metallic Nanoparticles via ..
115. Ge S, Shi X, Sun K, Li C, Baker JR, Banaszak Holl MM andOrr BG. A facile hydrothermal synthesis of iron oxide nanoparticles with tunable magnetic properties. 2009;13:13593-9
44. Yi DK, Selvan ST, Lee SS, Papaefthymiou GC, Kundaliya D, Ying JY. Silica-coated nanocomposites of magnetic nanoparticles and quantum dots. 2005;127:4990-1
metal oxide nanoparticles stand out as one of
One of the most notable differences between metal oxide aerogels and silica aerogels is that many metal oxide aerogels are often brilliantly colored. It is important to remember that the bluish cast characteristic of a silica aerogel is a result of Rayleigh scattering by nanoparticles which make up the aerogel backbone, and that silica itself is not blue. Similarly, aerogels of metal oxides which are white as powders and clear in their crystalline form (such as alumina, titania , and zirconia among others) look like silica aerogels–transparent with bluish Rayleigh scattering, and perhaps occasionally somewhat cloudy white. However, many metal oxides (such as chromium oxide and iron oxide) exhibit bright coloring as both powders and crystals, and are in fact used in dyes, paints, and glazes because of this. As a result, aerogels of these oxides are also brightly colored–iron oxide aerogels are Martian red, for example. Below are some of the colors associated with different metal oxide aerogels.
In recent years, multifunctional nanoparticles (NPs) consisting of either metal (e.g. Au), or magnetic NP (e.g. iron oxide) with other fluorescent components such as quantum dots (QDs) or organic dyes have been emerging as versatile candidate systems for cancer diagnosis, therapy, and macromolecule delivery such as micro ribonucleic acid (microRNA). This review intends to highlight the recent advances in the synthesis and application of multifunctional NPs (mainly iron oxide) in theranostics, an area used to combine therapeutics and diagnostics. The recent applications of NPs in miRNA delivery are also reviewed.
the nonaqueous synthesis of metal oxide …
In the mid-1990’s, Drs. Tom Tillotson, Alex Gash, Joe Satcher, John Poco, Larry Hrubesh, and Randall Simpson at Lawrence Livermore National Laboratory developed a new technique for synthesizing metal oxide gels: epoxide-assisted gelation of metal salts. This technique proved to not only enable preparation of metal oxide gels previously not possible, but also made synthesis of metal oxide gels much easier and resulted in stronger gels (and thus aerogels) with much better monolithicity. Gash further developed the technique in the early 2000’s by identifying the underlying mechanisms and extending it to many new elements. For this reasons the technique is commonly referred to as the “Gash Prep”.
In this technique, a hydrated metal salt (such as a nitrate or a chloride) is dissolved in a solvent (such as water, ethanol, or half-water/half-ethanol), to which an epoxide (such as propylene oxide or epichlorohydrin) is added dropwise. The metal salts exist as some sort of aquo complex in solution (that is, they have water ligands attached to them). The epoxide then acts as a proton scavenger, stealing a proton away from the metal complex and protonates itself, resulting in an irreversible ring-opening reaction. The pH of the system, in turn, gently increases, and aquo-hydroxy metal complexes form. These species, which contain M-OH sites, can then condense together to form metal-oxygen-metal bridges (similar to the way Si-OH groups condense together to form silicon-oxygen-silicon bridges)–the necessary connectivity for producing a metal oxide gel. Upon supercritical drying of the resulting gel, a metal oxide aerogel is produced.
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in the chemical synthesis of copper nanoparticles is ..
Our group has been actively involved in the synthesis of QDs and magnetic QDs (MQDs) [-]. We have successfully demonstrated the magnetic and fluorescent properties of Fe2O3-CdSe MQDs, silica -coated QDs or MQDs and their application in cell labeling (Figure ) . The silanization using aminopropyl triethoxysilane (APS) in a reverse microemulsion produced thin silica coating on bare CdSe QDs or Fe2O3-CdSe MQD with surface NH2 groups. The methoxy groups of APS were hydrolyzed and condensed with another APS, exposing surface amine groups on the silanized QDs (SiO2/QDs) for conjugation with oleyl-O-poly(ethyleneglycol)-succinyl-N-hydroxysuccinimidyl ester, denoted as bio-anchored membrane (BAM). The reaction between the amine group and NHS ester resulted in a covalent amide bond formation, leaving the exposed oleyl group for the effective targeting of cell membrane. The labeling of live cell membranes (HepG2 human liver cancer cells and NIH-3T3 mouse fibroblast cells) using confocal laser scanning microscopy (CLSM) indicated the successful conjugation of silica-coated QDs or MQDs with BAM.
Green Synthesis of Magnesium Oxide Nanoparticles
In another interesting work, Louie and coworkers have reported the synthesis of a reversible T2 contrast agent that is capable of modulating the relaxation time in response to light irradiation . A spiropyran (SP) derivative that changes conformation between hydrophilic and hydrophobic isomers in response to light, has been covalently attached to dextran sulfate coated iron oxide nanoparticles (ADIO). The light induced reversible aggregation of MNPs has been found to modulate the T2 relaxation time (Figure ).
Synthesis and characterization of ZnO nanoparticles.
Although many synthetic routes have been developed for the preparation of iron oxide core with tunable shape, size and magnetization, several challenges remain for the naked SPIONs in terms of stem cell labeling, including: (i) poor water solubility and tendency of aggregation due to large surface/volume ratio; (ii) low cellular uptake efficiency; (iii) potential toxicity. To address these problems, the most straightforward and effective method seems to be coating the iron oxide core by a layer. The nature of the surface coatings and modification methods determine the physical and biologic properties such as the overall size, surface charge, coating density, toxicity and degradability, which finally affect the fate of SPIONPs in the cells [, ]. This following section focuses on the currently used surface modification materials (e.g. PLL, PEI, chitosan, PEG, citric acid and so on) and methods (e.g. coating, post-synthesis coatings including blending, polymerization, ligand exchange) for the SPIONs applied for stem cell labeling and tracking. The influence of these factors on labeling efficiency and biocompatibility is also discussed.
Synthesis of Metal Oxide Nanoparticles and Its …
Heparin is a highly sulfated glycosaminoglycan molecule that interacts with various proteins containing heparin-binding domains within the extracellular matrix milieu. It has been widely used in drug delivery systems and tissue engineering to improve the biocompatibility and blood compatibility of biomaterials . Recently, Lee and coworkers  synthesized SPIONs coated with unfractionated heparin (UFH-SPIOs) by coating (Figure ). The uptake efficiency of UFH-SPIO without the aid of transfection agents was greater than that of dextran coated SPIO by approximately 3 folds when treated for 1 h. This was because the coating of heparin on the surface of NP increased its hydrophilicity, which promoted cell attachment to the NP surface. When the UFH-SPIO-labeled hMSCs were transplanted into the left renal subcapsular membranes of nude mice, they were successfully visualized and detected by 2 weighted MRI imaging after a month.
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