共查询到20条相似文献,搜索用时 0 毫秒
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The transport of guest molecules between adjacent pore channels (cross-wall transport) is the limiting factor in the release of guest molecules from SBA-3-like fibers. This specific mode of diffusion is identified by microscopic observation and studied quantitatively in a UV/Vis-monitored release experiment. Analysis of release curves reveals that the external particle surface offers resistance to the guest molecules passing through it (external diffusion barrier). This barrier is native to as-synthesized fibers and can be effectively modified to slow down the release. Extremely effective slowdown is achieved by deposition of a nanometer-thick layer of sodium silicate, that is, the guest molecules are then safely stored in the particles. 相似文献
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Barry NP Zava O Dyson PJ Therrien B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(35):9669-9677
A series of large cationic hexanuclear metalla-prisms, [Ru(6)(p-iPrC(6)H(4)Me)(6)(tpt)(2)(donq)(3)](6+), [Ru(6)(p-iPrC(6)H(4)Me)(6)(tpt)(2)(doaq)(3)](6+) and [Ru(6)(p-iPrC(6)H(4)Me)(6)(tpt)(2)(dotq)(3)](6+), composed of p-cymene-ruthenium building blocks bridged by OO∩OO ligands (donq=5,8-dioxido-1,4-naphthoquinonato; doaq=5,8-dioxido-1,4-anthraquinonato, dotq=6,11-dioxido-5,12-naphthacenedionato) and connected by two 2,4,6-tripyridin-4-yl-1,3,5-triazine (tpt) panels, which encapsulate the guest molecules 1-(4,6-dichloro-1,3,5-triazin-2-yl)pyrene and Pd(acac)(2), have been prepared. The host-guest properties of these water-soluble delivery systems were studied in solution by NMR and fluorescence spectroscopy, providing the stability constants (K) for these host-guest systems. Moreover, the ability of the hosts to deliver the guests into cancer cells was evaluated and the uptake mechanism studied; the rate of release of the guest molecule was found to depend on the portal size of the host. 相似文献
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Mellaerts R Aerts CA Van Humbeeck J Augustijns P Van den Mooter G Martens JA 《Chemical communications (Cambridge, England)》2007,(13):1375-1377
This in vitro study reports on the enhanced release of the hydrophobic drug itraconazole from the ordered mesoporous SBA-15 silica material and on the existence of a critical mesopore diameter for enhancing release. 相似文献
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Laughrey ZR Gibb CL Senechal T Gibb BC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(1):130-139
The synthesis of three different nanoscale molecular hosts is reported. These cavitands each possess a highly preorganized cavity with an open portal (nearly 1 nm wide), by which guests can enter and egress the cavity. Additionally, these hosts are deep-functionalized with a crown of weakly acidic benzal C-H groups which can form a variety of noncovalent interactions with guest molecules residing within the cavity. Thirty-one guests were examined for their propensity to form complexes with the hosts. Guests that possess halogen atoms were the strongest binders, suggesting the formation of polydentate C-H triplebond X-R hydrogen bonds with the deep crown of benzal hydrogens. Exchange rates between the free and bound states were noted to be dependent on the size of the guest and the solvent used to study complexation. In general, stronger binding and slower exchange were noted for complexations carried out in DMSO with highly complementary guests. The orientation of each guest within the cavity was determined using either EXSY NMR spectroscopy or (1)H NMR shift data. Cumulatively these results showed that the principal factors directing orientation were interactions with the benzal groups and the type of solvent. Van't Hoff analyses of selected complexations were also carried out. As well as revealing that all complexations were entropically unfavorable, these experiments provided support for guest orientation determinations, and gave an estimation that the formation of a C-H triplebond I-R hydrogen bond releases between 1 and 1.5 kcal mol(-1). 相似文献
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A multifunctional drug delivery system based on MCM-41-type mesoporous silica nanoparticles is described that behaves as if nanogates were covalently attached to the outlets of the mesopores through a highly acid-sensitive benzoic-imine linker. Tumor-specific uptake and intracellular delivery results from the pH-dependent progressive hydrolysis of the benzoic-imine linkage that starts at tumor extracellular pH = 6.8 and increases with decreasing pH. The cleavage of the benzoic-imine bond leads to the removal of the polypseudorotaxane caps and subsequent release of the payload drugs at tumor sites. At the same time, the carrier surface becomes positively charged, which further facilitates cellular uptake of the nanocarriers, thus offering a tremendous potential for targeted tumor therapy. 相似文献
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Isabel Izquierdo-Barba Edesia Sousa Juan Carlos Doadrio Antonio Luis Doadrio Joaquín Pérez Pariente Africa Martínez Florence Babonneau María Vallet-Regí 《Journal of Sol-Gel Science and Technology》2009,50(3):421-429
Ordered mesoporous materials exhibit potential features to be used as controlled drug delivery systems, including their wide
range of chemical compositions and their outstanding textural and structural properties. Therefore, it is possible to control
the drug release kinetics by tailoring such parameters. In this paper, mesoporous materials such as MCM-48 and SBA-15, which
present different pore sizes (3.7 and 8.8 nm) and structural characteristics (3D-bicontinuous cubic and 2D-hexagonal, respectively)
have been synthesized to evaluate their application as drug delivery system and to determine their influence on release kinetic
of ibuprofen. Moreover, a chemical modification of the SBA-15 mesoporous material with octadecyltrimethoxysilane has also
been performed to study its influence on the release rate of ibuprofen. The structural characteristics (3D cubic and 2D hexagonal
pore system) do not affect the release kinetic profiles of ibuprofen. On the contrary, the pore size affects highly to the
release kinetic profiles from first-order kinetic to zero-order kinetic for MCM-48 and SBA-15, respectively. Moreover, the
importance of surface functionalization was demonstrate through the very fast delivery of ibuprofen from SBA-15 mesoporous
materials functionalized with octadecyl chains. 相似文献