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81.
Water-dispersible sugar-coated iron oxide nanoparticles. An evaluation of their relaxometric and magnetic hyperthermia properties 总被引:1,自引:0,他引:1
Lartigue L Innocenti C Kalaivani T Awwad A Sanchez Duque Mdel M Guari Y Larionova J Guérin C Montero JL Barragan-Montero V Arosio P Lascialfari A Gatteschi D Sangregorio C 《Journal of the American Chemical Society》2011,133(27):10459-10472
Synthesis of functionalized magnetic nanoparticles (NPs) for biomedical applications represents a current challenge. In this paper we present the synthesis and characterization of water-dispersible sugar-coated iron oxide NPs specifically designed as magnetic fluid hyperthermia heat mediators and negative contrast agents for magnetic resonance imaging. In particular, the influence of the inorganic core size was investigated. To this end, iron oxide NPs with average size in the range of 4-35 nm were prepared by thermal decomposition of molecular precursors and then coated with organic ligands bearing a phosphonate group on one side and rhamnose, mannose, or ribose moieties on the other side. In this way a strong anchorage of the organic ligand on the inorganic surface was simply realized by ligand exchange, due to covalent bonding between the Fe(3+) atom and the phosphonate group. These synthesized nanoobjects can be fully dispersed in water forming colloids that are stable over very long periods. Mannose, ribose, and rhamnose were chosen to test the versatility of the method and also because these carbohydrates, in particular rhamnose, which is a substrate of skin lectin, confer targeting properties to the nanosystems. The magnetic, hyperthermal, and relaxometric properties of all the synthesized samples were investigated. Iron oxide NPs of ca. 16-18 nm were found to represent an efficient bifunctional targeting system for theranostic applications, as they have very good transverse relaxivity (three times larger than the best currently available commercial products) and large heat release upon application of radio frequency (RF) electromagnetic radiation with amplitude and frequency close to the human tolerance limit. The results have been rationalized on the basis of the magnetic properties of the investigated samples. 相似文献
82.
Smith NM Labrunie G Corry B Tran PL Norret M Djavaheri-Mergny M Raston CL Mergny JL 《Organic & biomolecular chemistry》2011,9(17):6154-6162
A series of novel 2,4,6-triarylpyridines have been synthesized and their interactions with intramolecular G-quadruplexes have been measured by F?rster Resonance Energy Transfer (FRET) melting and Fluorescent Intercalator Displacement (FID) assays. A few of these compounds exhibit stabilization of G4-DNA that is comparable to other benchmark G4-DNA ligands with fair to excellent G4-DNA vs. duplex selectivity and significant cytotoxicity towards HeLa cells. The nature of the 4-aryl substituents along with side chain length governs the G4-DNA stabilization ability of the compounds. In addition, we demonstrate that there is a strong correlation between the ability of the compounds to stabilize the same G4-DNA sequence in K(+) and Na(+) conditions and a strong correlation between the ability of the compounds to stabilize different G4-DNA sequences in K(+) or Na(+) buffer. 相似文献
83.
Okadaic acid (OA), responsible for gastrointestinal problems, inhibits protein phosphatase 2A (PP2A). Therefore, the inhibition exerted by the toxin on PP2A could be used to detect the presence of OA in aqueous solution and in shellfish sample.In this work, two commercial PP2As (from ZEU Immunotec and Millipore) and one produced by molecular engineering (from GTP Technology) were tested. Enzymes were used in solution and also immobilized within a polymeric gel. In solution, best performances were obtained using PP2A purchased from ZEU Immunotec (Spain). OA was detected in aqueous solution in concentration as low as 0.0124 μg L−1 using the enzyme from ZEU Immunotec whereas the detection limits were 0.47 μg L−1 and 0.123 μg L−1 with PP2As from Millipore and GTP Technology, respectively. Considering that the immobilization step contributes to stabilize the PP2A activity, enzymes were entrapped within a photopolymer and an agarose gel. These different polymeric matrices were optimized, tested and compared. Agarose gel seems to be a good alternative to the photopolymer largely used in our group. For instance, the IC50 value obtained with the test based on PP2A from ZEU Immunotec immobilized within an agarose gel was 1.98 μg L−1. This value was 1.8-fold lower than those obtained with the photopolymer test using the same enzyme. The proposed test is sensitive, fast and does not require expensive equipment. To evaluate the efficiency of the assay, PP inhibition tests based on PP2A from ZEU Immunotec in solution or immobilized within a gel were used for OA detection in contaminated shellfish. 相似文献
84.
Rodrigues AC Nascimento ML Bragatto CB Souquet JL 《The Journal of chemical physics》2011,135(23):234504
Conductivity data of the xAgI(1 - x)AgPO(3) system (0 ≤ x ≤ 0.5) were collected in the liquid and glassy states. The difference in the dependence of ionic conductivity on temperature below and above their glass transition temperatures (T(g)) is interpreted by a discontinuity in the charge carrier's mobility mechanisms. Charge carrier displacement occurs through an activated mechanism below T(g) and through a Vogel-Fulcher-Tammann-Hesse mechanism above this temperature. Fitting conductivity data with the proposed model allows one to determine separately the enthalpies of charge carrier formation and migration. For the five investigated compositions, the enthalpy of charge carrier formation is found to decrease, with x, from 0.86 to 0.2 eV, while the migration enthalpy remains constant at ≈0.14 eV. Based on these values, the charge carrier mobility and concentration in the glassy state can then be calculated. Mobility values at room temperature (≈10(-4) cm(2) V(-1) s(-1)) do not vary significantly with the AgI content and are in good agreement with those previously measured by the Hall-effect technique. The observed increase in ionic conductivity with x would thus only be due to an increase in the effective charge carrier concentration. Considering AgI as a weak electrolyte, the change in the effective charge carrier concentration is justified and is correlated to the partial free energy of silver iodide forming a regular solution with AgPO(3). 相似文献
85.
We investigate the problem of heat conduction across molecular junctions connecting two nanoparticles, both in vacuum and in a liquid environment, using classical molecular dynamics simulations. In vacuum, the well-known result of a length independent conductance is recovered; its precise value, however, is found to depend sensitively on the overlap between the vibrational spectrum of the junction and the density of states of the nanoparticles that act as thermal contacts. In a liquid environment, the conductance is constant up to a crossover length, above which a standard Fourier regime is recovered. 相似文献
86.
Jean-Louis Féménias 《Journal of Molecular Spectroscopy》2005,232(1):80-101
Applications of the χ2 test, the F test, the Durbin-Watson d test, and the f (or Sign) test, to examples of correlated data treatment, show important drawbacks with the d test and (apparently) with the f test. An analytical approach based on residual analysis suggests an improvement in their use that leads to better results at lowest order; it also points out a distinction between goodness-of-fit tests, as the f test, and goodness-of-modeling tests, as the χ2 and F tests. The residual analysis method is applied to the same examples; it looks faster, simpler, and often more accurate than the classical ones. 相似文献
87.
While the striking structures (e.g. nest architecture, trail networks) of insect societies may seem familiar to many of us, the understanding of pattern formation still constitutes a challenging problem. Over the last two decades, self-organization has dramatically changed our view on how collective decision-making and structures may emerge out of a population of ant workers having each their own individuality as well as a limited access to information. A variety of collective behaviour spontaneously outcome from multiple interactions between nestmates, even when there is no directing influence imposed by an external template, a pacemaker or a leader. By focussing this review on foraging structures, we show that ant societies display some properties which are usually considered in physico-chemical systems, as typical signatures of self-organization. We detail the key role played by feed-back loops, fluctuations, number of interacting units and sensitivity to environmental factors in the emergence of a structured collective behaviour. Nonetheless, going beyond simple analogies with non-living self-organized patterns, we stress on the specificities of social structures made of complex living units of which the biological features have been selected throughout the evolution depending on their adaptive value. In particular, we consider the ability of each ant individual to process information about environmental and social parameters, to accordingly tune its interactions with nestmates and ultimately to determine the final pattern emerging at the collective level. We emphasize on the parsimony and simplicity of behavioural rules at the individual level which allow an efficient processing of information, energy and matter within the whole colony. 相似文献
88.
The field of the rapid characterization of products by HS-MS is reviewed. The general principle of HS-MS systems consists of introducing volatile components present in the HS of a sample without prior chromatographic separation into the ionization chamber of a mass spectrometer. The spectrum resulting from simultaneous ionization and fragmentation of the mixture of molecules introduced constitutes a “fingerprint” that is characteristic of the product being analyzed. Exploitation of this spectral information allows one determine the composition of the sample. 相似文献
89.
A new convenient preparation of samarium dibromide in THF is reported. Pinacol coupling reactions using SmBr2 in catalytic amounts together with mischmetall as a coreductant have been performed with a variety of carbonyl compounds. 相似文献
90.
R. Kalfat N. Gharbi S. Romdhane J.-L. Fave A. Chaïeb M. Majdoub 《Journal of Sol-Gel Science and Technology》1998,13(1-3):439-443
Photoluminescence of a polysiloxane gel film incorporating a partially conjugated copolymer polyether-polyphenylenevinylene (PEPPV) has been studied and compared with results obtained from bulk and vacuum evaporated films of the same starting material. The evaporation clearly affects the distribution of lengths of the conjugated parts, yet the incorporation in the gel matrix induces only slight changes in the spectroscopic properties of the polymer. 相似文献