Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.2.1.1 (ACS)
 78,556 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The fluorescent dye Alexa Fluor 488 or the anticancer drug doxorubicin is attached to the surface and inner pore walls of mesoporous Si particles by covalent attachment, and the oxidation-induced release of each molecule is studied. The molecules are bound to the Si matrix using a 10-undecenoic acid linker, which is attached by thermal hydrosilylation. Loading capacity of the microparticles using this method is approximately 0.5 and 45 mg/g of porous Si microparticle for Alexa Fluor 488 and doxorubicin, respectively. The Si-C-bound assembly is initially stable in aqueous solution, although oxidation of the underlying Si matrix results in conversion to silicon oxide and slow release of the linker-molecule complex by hydrolysis of the Si-O attachment points. When the attached molecule is a fluorophore (Alexa Fluor 488 or doxorubicin), its fluorescence is effectively quenched by the semiconducting silicon matrix. As the particle oxidizes in water, the fluorescence intensity of the attached dye increases due to growth of the insulating silicon oxide layer and, ultimately, dye release from the surface. The recovery of fluorescence in the microparticle and the release of the molecule into solution are monitored in real-time by fluorescence microscopy. Both processes are accelerated by introduction of the oxidizing species peroxynitrite to the aqueous solution. The oxidation-triggered release of the anticancer drug doxorubicin to HeLa cells is demonstrated.
ACS Nano 2008 Nov 25
PMID:Oxidation-triggered release of fluorescent molecules or drugs from mesoporous Si microparticles. 1920 8

An atomic force microscope and the colloidal probe technique are used to probe the interaction between a hydrophobic particle and a hydrophobic surface in water. The characteristics of the observed force curves strongly suggest that a gas bubble is formed when the particle is moved toward the surface and that the bubble ruptures when the particle subsequently is retracted from the surface. We demonstrate that this type of interaction is not unique for hydrophobic surfaces in water since the interaction between hydrophilic surfaces in air provides very similar force curves. However, the interaction between hydrophobic surfaces vanish if water is replaced by an organic solvent with low polarity. The bridging bubble model is employed to explain the hysteresis observed between approach and retraction force traces and experimental conditions where the hysteresis can be almost eliminated are identified. Finally, it is demonstrated that the hydrophobic interaction is strongly temperature dependent and this dependence can be attributed mainly to the decreasing solubility of air in water with increasing temperature.
ACS Nano 2008 Sep 23
PMID:Force trace hysteresis and temperature dependence of bridging nanobubble induced forces between hydrophobic surfaces. 1920 20

We demonstrate the synthesis of a series of spin-labeled curved oligomers to determine their end-to-end lengths and distance distributions using electron spin resonance. We synthesize shape-persistent macromolecules from conformationally restricted, asymmetric monomers that are coupled through pairs of amide bonds to create water-soluble, spiro-ladder oligomers with well-defined three-dimensional structures. We synthesized seven different macromolecules, each containing eight monomers but differing in the sequence to create macromolecules with different curved shapes. The ends of the oligomers were labeled with nitroxide spin probes, and double electron-electron resonance (DEER) electron spin resonance (ESR) experiments were carried out to obtain quantitative information about the shapes and flexibility of the oligomers. The most probable end-to-end distance of the oligomers ranges from 23 to 36 A, a range of length that we previously accessed by assembling rod-like homo-oligomers that contain 4-8 bisamino acid monomers. The relative distances measured for the oligomers confirm that, by varying the sequence of an oligomer, we are able to control its shape. The shapes of the ESR-derived population distributions allow us to compare the degree of shape persistence and flexibility of spiro-ladder oligomers to other well-studied nanoscale molecular structures such as p-phenylethynylenes.
ACS Nano 2008 Sep 23
PMID:Distance distributions of end-labeled curved bispeptide oligomers by electron spin resonance. 1920 25

Novel nanoporous poly(3,4-ethylenedioxythiophene) (PEDOT) films with basalt-like surface morphology are successfully obtained via a one-step, vapor phase process of oxidative chemical vapor deposition (oCVD) by introducing a new oxidant, CuCl(2). The substrate temperature of the oCVD process is a crucial process parameter for controlling electrical conductivity and conjugation length. Moreover, the surface morphology is also systemically tunable through variations in substrate temperature, a unique advantage of the oCVD process. By increasing the substrate temperature, the surface morphology becomes more porous, with the textured structure on the nanometer scale. The size of nanopores and fibrils appears uniformly over 25 mm x 25 mm areas on the Si wafer substrates. Conformal coverage of PEDOT films grown with the CuCl(2) oxidant (C-PEDOT) is observed on both standard trench structures with high aspect ratio and fragile surfaces with complex topology, such as paper, results which are extremely difficult to achieve with liquid phase based processes. The tunable nanoporosity and its conformal coverage on various complex geometries are highly desirable for many device applications requiring controlled, high interfacial area, such as supercapacitors, Li ion battery electrodes, and sensors. For example, a highly hydrophilic surface with the static water contact angle down to less than 10 degrees is obtained solely by changing surface morphology. By applying fluorinated polymer film onto the nanoporous C-PEDOT via initiative chemical vapor deposition (iCVD), the C-PEDOT surface also shows the contact angle higher than 150 degrees . The hierarchical porous structure of fluorinated polymer coated C-PEDOT on a paper mat shows superhydrophobicity and oil repellency.
ACS Nano 2008 Sep 23
PMID:Conformal coverage of poly(3,4-ethylenedioxythiophene) films with tunable nanoporosity via oxidative chemical vapor deposition. 1920 37

Cisplatin (CDDP) was incorporated inside single-wall carbon nanohorns with holes opened (SWNHox) by a nanoprecipitation method that involved dispersion of CDDP and SWNHox in a solvent followed by the solvent evaporation. The incorporated CDDP quantity increased from the previously reported value of 15 to 46%, and the total released quantity of CDDP also increased from 60 to 100% by changing the solvent from dimethylformamide to water. Concurrently, in vitro anticancer efficiency of CDDP@SWNHox increased to 4-6 times greater than that of the intact CDDP. In vivo, CDDP@SWNHox intratumorally injected to transplanted tumors of mice suppressed the tumor growth more than the intact CDDP. We observed that CDDP@SWNHox adhered to the cell surfaces in vitro and stayed within the tumor tissues in vivo. Therefore, we think that the CDDP released from SWNHox realized high concentrations locally at the cells in vitro and in the tissues in vivo and could efficiently attack the tumor cells. We also found that SWNHox itself had an in vivo anticancer effect, which might increase the anticancer activities of CDDP@SWNHox.
ACS Nano 2008 Oct 28
PMID:Enhancement of in vivo anticancer effects of cisplatin by incorporation inside single-wall carbon nanohorns. 1920 52

In this study, we report a rapid sonochemical synthesis of monodisperse nonaggregated Fe(3)O(4)@SiO(2) magnetic nanoparticles (NPs). We found that coprecipitation of Fe(II) and Fe(III) in aqueous solutions under the effect of power ultrasound yields smaller Fe(3)O(4) NPs with a narrow size distribution (4-8 nm) compared to the silent reaction. Moreover, the coating of Fe(3)O(4) NPs with silica using an alkaline hydrolysis of tetraethyl orthosilicate in ethanol-water mixture is accelerated many-fold in the presence of a 20 kHz ultrasonic field. The thickness of the silica shell can be easily controlled in the range of several nanometers during sonication. Mossbauer spectra revealed that nonsuperparamagnetic behavior of obtained core-shell NPs is mostly related to the dipole-dipole interactions of magnetic cores and not to the particle size effect. Core-shell Fe(3)O(4)@SiO(2) NPs prepared with sonochemistry exhibit a higher magnetization value than that for NPs obtained under silent conditions owing to better control of the deposited silica quantities as well as to the high speed of sonochemical coating, which prevents the magnetite from oxidizing.
ACS Nano 2008 May
PMID:Sonochemical approach to the synthesis of Fe(3)O(4)@SiO(2) core-shell nanoparticles with tunable properties. 1920 81

Luminescent silicon quantum dots (Si QDs) have great potential for use in biological imaging and diagnostic applications. To exploit this potential, they must remain luminescent and stably dispersed in water and biological fluids over a wide range of pH and salt concentration. There have been many challenges in creating such stable water-dispersible Si QDs, including instability of photoluminescence due their fast oxidation in aqueous environments and the difficulty of attaching hydrophilic molecules to Si QD surfaces. In this paper, we report the preparation of highly stable aqueous suspensions of Si QDs using phospholipid micelles, in which the optical properties of Si nanocrystals are retained. These luminescent micelle-encapsulated Si QDs were used as luminescent labels for pancreatic cancer cells. This paves the way for silicon quantum dots to be a valuable optical probe in biomedical diagnostics.
ACS Nano 2008 May
PMID:Biocompatible luminescent silicon quantum dots for imaging of cancer cells. 1920 83

Drug delivery, magnetic resonance and fluorescence imaging, magnetic manipulation, and cell targeting are simultaneously possible using a multifunctional mesoporous silica nanoparticle. Superparamagnetic iron oxide nanocrystals were encapsulated inside mesostructured silica spheres that were labeled with fluorescent dye molecules and coated with hydrophilic groups to prevent aggregation. Water-insoluble anticancer drugs were delivered into human cancer cells; surface conjugation with cancer-specific targeting agents increased the uptake into cancer cells relative to that in non-cancerous fibroblasts. The highly versatile multifunctional nanoparticles could potentially be used for simultaneous imaging and therapeutic applications.
ACS Nano 2008 May
PMID:Multifunctional inorganic nanoparticles for imaging, targeting, and drug delivery. 1920 85

The influence of coating on interparticle interactions in ferrofluids has been investigated using various techniques such as Mossbauer spectroscopy, magnetometry, transmission electron microscopy, photon correlation spectroscopy, X-ray diffraction, X-ray photoelectron, and resonance micro-Raman spectroscopy. Aging and spin-glass-like behavior was investigated in frozen ferrofluids of various concentrations from dense, initial value of 40 mg of coated nanoparticles per 1 mL of water, to dilute 1:10 (4 mg/mL). The as-prepared nanoparticles, core size 7-8 nm, were subsequently coated with a gummic acid corona of 20 nm thickness, which was observed to prevent agglomeration and to delay aggregation even in dense ferrofluids. The resulting separation of magnetic cores due to the coating eliminated all magnetic interparticle interaction mechanisms, such as exchange and dipoledipole, thus ensuring no aging effects of the magnetic particle system, as manifested in particle agglomeration and precipitation.
ACS Nano 2008 May
PMID:No aging phenomena in ferrofluids: the influence of coating on interparticle interactions of maghemite nanoparticles. 1920 95

Nanocrystalline ZrO(2) samples with narrow size distributions and mean particle sizes below 10 nm have been synthesized in a continuous flow reactor in near and supercritical water as well as supercritical isopropyl alcohol using a wide range of temperatures, pressures, concentrations and precursors. The samples were comprehensively characterized by powder X-ray diffraction (PXRD), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS), and the influence of the synthesis parameters on the particle size, particle size distribution, shape, aggregation and crystallinity was studied. On the basis of the choice of synthesis parameters either monoclinic or tetragonal zirconia phases can be obtained. The results suggest a critical particle size of 5-6 nm for nanocrystalline monoclinic ZrO(2) under the present conditions, which is smaller than estimates reported in the literature. Thus, very small monoclinic ZrO(2) particles can be obtained using a continuous flow reactor. This is an important result with respect to improvement of the catalytic properties of nanocrystalline ZrO(2).
ACS Nano 2008 May
PMID:Critical size of crystalline ZrO(2) nanoparticles synthesized in near- and supercritical water and supercritical isopropyl alcohol. 1920 4


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>