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1.
Nano Lett ; 17(7): 4497-4501, 2017 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-28617606

RESUMO

Additive manufacturing processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymerization, which is the most versatile technology enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process. Light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the metal tip, enabling redox reactions to form radicals in aerobic conditions. In particular, we demonstrate their use in 3D printing in water, where they simultaneously form hydroxyl radicals for the polymerization and consume dissolved oxygen that is a known inhibitor. We also demonstrate their potential for two-photon polymerization due to their giant two-photon absorption cross section.

2.
J Colloid Interface Sci ; 464: 167-74, 2016 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-26615512

RESUMO

HYPOTHESIS: Surface modification of nanoparticles during aerosol or gas-phase synthesis, followed by direct transfer into liquid media can be used to produce stable water-dispersed nanoparticle suspensions. EXPERIMENT: This work investigates a single-step, aerosol process for in-situ surface-modification of nanoparticles. Previous studies have used a two-step sublimation-condensation mechanism following droplet drying, for surface modification, while the present process uses a liquid precursor containing two solutes, a matrix lipid and a surface modifying agent. A precursor solution in chloroform, of stearic acid lipid, with 4 %w/w of surface-active, physiological molecules [1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol)-sodium salt (DPPG) or 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy (polyethylene glycol) 2000]-ammonium salt (DPPE-PEG)] was processed in an aerosol reactor at a low gas temperatures. The surface modified nanoparticles were characterized for morphology, surface composition and suspension properties. FINDINGS: Spherical, surface-modified lipid nanoparticles with median mobility diameters in the range of 105-150nm and unimodal size distributions were obtained. Fourier transform infra-red spectroscopy (FTIR) measurements confirmed the presence of surface-active molecules on external surfaces of modified lipid nanoparticles. Surface modified nanoparticles exhibited improved suspension stability, compared to that of pure lipid nanoparticles for a period of 30days. Lowest aggregation was observed in DPPE-PEG modified nanoparticles from combined electrostatic and steric effects. The study provides a single-step aerosol method for in-situ surface modification of nanoparticles, using minimal amounts of surface active agents, to make stable, aqueous nanoparticle suspensions.


Assuntos
Nanopartículas/química , Aerossóis , Tamanho da Partícula , Propriedades de Superfície , Suspensões , Água/química
3.
Int J Pharm ; 430(1-2): 228-37, 2012 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-22469694

RESUMO

The crystallinity of drug-loaded lipid nanoparticles is believed to affect drug release rates; however, effective control over lipid crystallinity has not been achieved by current lipid nanoparticle preparation methods. The present study investigates control over the crystallinity of drug-loaded nanoparticle aerosol lipid matrices (NALM) through differences in evaporation rates of precursor solution drops and the subsequent control over drug release rates from these matrices. Gefitinib-loaded NALM were synthesized in an aerosol reactor using precursor solutions of gefitinib and stearic acid at a ratio of 1:4 w/w in organic solvents with high (dichloromethane) and low (ethyl acetate and chloroform) vapor pressures. Mean mobility diameter measured using a scanning mobility particle sizer was in the range of 123-132 nm with a unimodal distribution and a geometric standard deviation of 1.6-1.9. A layered particle structure was observed using transmission electron microscopy, which suggests partial drug enrichment in the surface layer. Higher drug loading (20% w/w) and uniform entrapment efficiencies (∼100%) were achieved. The initial drug to lipid ratio (1:4 w/w) of the precursor solution was preserved in the synthesized lipid matrices. The crystallinity of the gefitinib-loaded lipid matrix was measured using X-ray diffraction and differential scanning calorimetry. In vitro drug release from gefitinib-loaded NALM in phosphate buffered saline (pH 7.2) over 10 days showed an initial fast release period followed by a prolonged sustained release period with varying release rates. Gefitinib-loaded NALM synthesized at higher evaporation rates exhibited lower degrees of crystallinity and faster drug releases. These results suggest the determinant role of lipid crystallinity manipulated by differing evaporation rates during aerosol synthesis on drug releases from nanometer-sized lipid matrices.


Assuntos
Antineoplásicos/química , Portadores de Fármacos , Nanopartículas , Quinazolinas/química , Solventes/química , Ácidos Esteáricos/química , Acetatos/química , Aerossóis , Varredura Diferencial de Calorimetria , Química Farmacêutica , Clorofórmio/química , Cristalização , Cristalografia por Raios X , Preparações de Ação Retardada , Composição de Medicamentos , Gefitinibe , Concentração de Íons de Hidrogênio , Cinética , Cloreto de Metileno/química , Microscopia Eletrônica de Transmissão , Nanotecnologia , Tamanho da Partícula , Solubilidade , Tecnologia Farmacêutica/métodos , Pressão de Vapor
4.
In Vivo ; 23(2): 303-7, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19414419

RESUMO

BACKGROUND: Recent reports regarding acetylsalicylic acid (ASA) and its metabolites suggest suppressive effects against mitomycin C (MMC)-induced genotoxicity in a mice chromosomal aberration assay. Keeping this in mind, the potential anti-genotoxic effect of the thio-analogue of salicylic acid namely thio-salicylic acid (TSA) was speculated upon. The present study investigated and compared the anti-genotoxic potential of ASA and TSA. MATERIALS AND METHODS: The study was performed in male swiss mice (20+/-2 g) using single-cell gel electrophoresis and a peripheral blood micronucleus assay. ASA and TSA (5, 10 or 20 mg/kg) were administered 15 minutes after MMC (1 mg/kg) once daily for 3 or 7 days. RESULTS: Both ASA and TSA significantly decreased the DNA damage induced by MMC as indicated by a decrease in the comet parameters in bone marrow cells and decreased frequencies of micronucleated reticulocytes in peripheral blood. CONCLUSION: The results clearly demonstrate the anti-genotoxic potential of ASA and TSA.


Assuntos
Mitomicina/farmacologia , Ácido Salicílico/farmacologia , Animais , Células da Medula Óssea , Ensaio Cometa , Dano ao DNA , Masculino , Camundongos , Testes para Micronúcleos , Testes de Mutagenicidade , Mutagênicos/toxicidade , Reticulócitos/metabolismo , Ácido Salicílico/química , Fatores de Tempo
5.
Phytother Res ; 21(12): 1221-7, 2007 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-17661327

RESUMO

Mitomycin C (MMC) is a highly active anticancer drug commonly used alone and in combination with other chemotherapeutic agents for the treatment of different cancers. Its bioactivated form critically damages the DNA present in both rapidly dividing cancerous cells as well as in normal cells. Genotoxicity in the normal cells makes this drug highly toxic; thereby decreasing its therapeutic index for clinical use. The study investigated the chemoprotective potential of American ginseng root extract against MMC by using the micronuclei test in a mouse test system. Pre-treatment with ginseng at doses 50 mg/kg and 100 mg/kg, p.o. for 3 and 7 days significantly decreased the frequency of micronucleated polychromatic erythrocytes (PCEs). Similar protective effects were also observed during co-treatment with ginseng at similar doses for 3 and 7 days. The present results indicate that American ginseng extract is capable of suppressing the chromosomal aberration induced by MMC in mice. Thus, American ginseng may be a potent chemoprotective agent against the toxicity of the anticancer drug, mitomycin C.


Assuntos
Antibióticos Antineoplásicos/efeitos adversos , Citoproteção/efeitos dos fármacos , Micronúcleos com Defeito Cromossômico/efeitos dos fármacos , Mitomicina/efeitos adversos , Panax , Extratos Vegetais/farmacologia , Animais , Masculino , Camundongos , Micronúcleos com Defeito Cromossômico/induzido quimicamente , Raízes de Plantas
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