RESUMO
Drug eluting stents (DESs) have revolutionized the interventional cardiology over the past decade since the first DES became commercially available in Europe in 2002. Compared to bare metal stents that are deployed to keep the vessel open by mechanical force, DESs have an additional function of reducing restenosis by the action of the drug on the target site. Coatings on the stent surface which ensure the maximum delivery of therapeutic agents to the target site with minimal systematic toxicity, also play an important role in adjusting the drug release profile. Coating material and technology not only affect the surface biocompatibility and the integrity maintenance during the implanting process, but also decide the way of drug delivering and transmitting from the coating. This paper reviews the basic principles of DES coating design, the categories of DES coatings, the commonly used clinical DES coatings and their efficiency in reducing restenosis, and finally provides the future perspectives for DES coatings.
Assuntos
Sistemas de Liberação de Medicamentos , Stents Farmacológicos , Materiais Biocompatíveis , Portadores de Fármacos , Ácido Láctico , Fosforilcolina , Polietilenos , Ácido Poliglicólico , Copolímero de Ácido Poliláctico e Ácido Poliglicólico , Desenho de Prótese , TitânioRESUMO
Owing to their unique structure and properties, carbon nanotubes (CNTs) have become the highlight of research since they were discovered. Part of the research interest lies in introducing them into solid state matrix to make them materialized. However, CNTs tend to aggregate in the matrix, which makes it difficult to make homogeneous composites. In order to solve this problem, we first modified the surface of CNTs by chemically bonding them to 3-aminopropyltrie-thoxysilane (NH2 (CH2)3Si(OC2H5)3, APTES) using three-step reactions, and then connected them to silica network by sol-gel technique. In the present paper, CNTs were first treated with HNO3 to get CNTs-COOH, which were then treated with SOCl2 to be transferred to CNTs-COCl, and finally CNTs-COCl reacted with APTES to get CNTs-APTES. After that, CNTs were introduced into silica net work through the individual hydrolysis of CNTs-APTES, tetrathyloxysilane (Si(OC2H5)4, TEOS) and 3-glycidoxy-propltrimethoxysilane (CH2OCHCH2O(CH2)3Si(OCH3)3, GPTMS) as sol-gel precursors, and the copolymerization of their hydrolysis products. FTIR and SEM were used to characterize the composition and microstructure of the obtained samples. (Owing to the connection of CNTs with silica network, little aggregation of CNTs was observed and high-quality CNTs/SiO2 composite gel glass was obtained. A model of CNTs/SiO2 network was also given.
Assuntos
Nanotecnologia/métodos , Nanotubos de Carbono/química , Dióxido de Silício/química , Géis/química , VidroRESUMO
In decades, metallo-phthalocyanines (MPcs) have undergone a renaissance because of their singular and unconventional physical properties. However, for the successful application of MPcs in practical devices, it is important to disperse MPc molecules into solid state matrix to fabricate MPc doped composite with desired properties. Inorganic glass is an ideal matrix because of its transparency and high environmental stability. One attractive approach to fabricating MPc/inorganic composite is sol-gel technique. In the present paper, silica gel glass matrix was prepared by hydrolysis and poly-condensation of tetraethyloxysilane. 1,2-dicyanobenzene and analytically pure soluble nickle salt were used as the nickle phthalocyanine (NiPc) reactants and chemical synthesis technique was used to prepare NiPc doped sol-gel materials at several temperatures. During the heat treatment, four 1, 2-dicyanobenzene molecules and one nickle ion collide to form a NiPc molecule. In-situ synthesizing process of NiPc in the pores of silica gel glass matrix was traced by UV/Vis absorption spectra. Owing to the remarkable absorption band of NiPc in visible region, quantity of in-situ synthesized NiPc was calculated by the absorbance at certain wavelength of 670 nm, using composites with physically doped NiPc as a reference. The in-situ synthesized kinetics was studied in detail and found to be consistent with Avrami-Erofeev equation The reaction grades were deduced to be 4.5, 4.5, 3.7, 3.2 and 1.9 respectively at temperatures of 180 degrees C, 185 degrees C, 190 degrees C, 195 degrees C and 200 degrees C, respectively.
Assuntos
Indóis/química , Níquel/química , Silanos/química , Absorção , Géis , Vidro/química , Temperatura Alta , Hidrólise , Isoindóis , Teste de Materiais , Microscopia Eletrônica de Varredura , Nanoestruturas/química , Nanotecnologia , Nitrilas/química , Tamanho da Partícula , Sílica Gel , Dióxido de Silício/químicaRESUMO
Linear and nonlinear optical properties of five kinds of zinc phthalocyanines (ZnPcs) were investigated using UV-Vis absorption spectra, fluorescence spectra and Z-scan measurements. The influence of concentrations on the optical properties of zinc phthalocyanine (ZnPc) was also studied. Linear optical results show that the five investigated ZnPcs are fluorescent, while nonlinear optical results show that they are effective reverse saturable absorption materials. The concentrations have drastically influenced the linear and nonlinear optical properties of ZnPc.
RESUMO
Optical limiting (OL) cycling performance and photostability of vanadyl phthalocyanines (VOPcs) and naphthalocyanines (VONcs) were studied. The results show that although vanadyl 2,11,20,29-tetra-tert-butyl-2,3-naphthalocyanine has the most pronounced OL effect originally, it is not a promising OL material due to its poor photostability. Meanwhile, vanadyl 2,9, 16,23-etraphenoxy-29H, 31H-phthalocyanine is considered to be a potential OL material, owing to its considerable OL effect and good photostability. A possible photochemical mechanism behind the reverse saturable absorption (RSA) and photolysis process of the studied species is proposed.
RESUMO
Optical limiting (OL) cycling behavior of chloroindium (III) phthalocyanine (InPcCl) solution was investigated by repeating Z-scan measurement up to 150 times, while photostability was characterized by changes in the UV-Vis absorption spectra during the process of laser irradiation and daylight illumination. The results show that InPcCl is stable against laser irradiation, leading to its good OL cycling behavior, although it features poor stability against daylight illumination. The possible mechanism behind this difference in photostability is proposed.
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The present paper reports the encapsulation of lead (II) tetrakis (4-cumylphenoxy)-phthalocyanine (PbPc(CP)4) into silica gel glass matrix to produce homogeneously doped composites by sol-gel technique. The existing state and structure of the doped PbPc(CP)4 were studied by UV-Vis absorption spectra and TEM images. Optical limiting properties were measured at 532 nm with 8 ns pulses. The results show that the doped PbPc(CP)4 molecules aggregate to form clusters in the gel glass composites, and PbPc(CP)4 has better optical limiting properties in the gel glass composites owing to the rigid structure of solid matrix.
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Nickel tetrasulfo-phthalocyanine (NiTSPc) was successfully doped into vinyltriethoxysilane (VTES)modified silicate gel glass by sol-gel technique, IR and UV-Vis spectral examination was carried out. The results show that vinyl has been introduced into SiO2 network, and the structure of gel glass is therefore changed. The encapsulation of NiTSPc does not make any noteworthy changes in the composition and structure of gel glass matrix. NiTSPc molecules are well dispersed in the organic modified matrix, and the phenomenon of aggregation is greatly suppressed.
RESUMO
The composition and structure evolution of carbon nanotube (CNT)/silica xerogel composites during the process of laser irradiation was traced by infrared (IR) spectra, Raman spectra, transmission electronic microscope (TEM) and pore structure analysis. The results of IR and Raman spectra show that during the process of laser irradiation the compositions of the composites do not make any noteworthy changes, while the matrix silica network becomes perfect and the doped CNTs become more graphitized. TEM images and pore structure analysis show that the SiO2 granules and the corresponding pore size increase after laser irradiation.
RESUMO
Nickle tetrasulfo-phthalocyanine (NiTSPc) and Lead phthalocyanine (PbPc) are introduced respectively into silica gel glass matrix by sol-gel technique. Homogeneously doped composites are produced, and optical limiting examination was carried out. The results show that the change in matrix composition, structure and sol-gel process will influence the chemical micro-environment and excited state physical process of doped metallo phthalocyanine, resulting in the change in composite's optical limiting behaviors.
RESUMO
One of the focal topics in the field of phthalocyanine research is its materialization for practical use. The present paper reports the encapsulation of gallium phthalocyanine chloride (GaPcCl) into silica gel glass to make homogeneously doped composite by sol-gel technique. The spectral properties of the composite gel glass were carried out by IR, UV-Vis and fluorescence measurements. The results show that the introduction of GaPcCl doesn't make noteworthy changes in the IR spectra of silica gel glass matrix. The absorption of GaPcCl dimers increases compared with DMF solution. The fluorescence intensity of GaPcCl is greatly enhanced in the composite gel glass.
RESUMO
Nickle phthalocyanine(NiPc) and Nickle tetrasulfo-phthalocyanine (NiTSPc) were introduced respectively into silica gel matrix by sol-gel technique. Composites were produced and their UV/Vis spectra were measured. The results show that the introduction of soluble tetrasulfo-substituents can greatly increase the solubility of phthalocyanine molecule, which is helpful for the steady co-existence of phthalocyanine in sol-gel hybrid and therefore beneficial to the production of homogeneous composite.
RESUMO
We report here the preparation of nickel tetrasulfo-phthalocyanine (NiTSPc)-doped silica xerogel matrix obtained by sol-gel technique. The evolution of silica matrix's texture and the rate during the sol-gel process, as well as silica xerogel's pore structure were studied. Dimerization behavior of NiTSPc molecules was characterized by electronic absorption spectra, and changes in the absorption spectra were correlated with various stages of the sol-gel process. The results show that in the composites NiTSPc concurs in the forms of monomer and dimer, and dimerization is stronger during the latter stages. The reason is given from the change in the micro-environment in which NiTSPc existed during the sol-gel process.