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1.
J Phys Condens Matter ; 29(25): 255501, 2017 Jun 28.
Artigo em Inglês | MEDLINE | ID: mdl-28516897

RESUMO

Intrinsic valley polarization can be obtained in VSe2 monolayers with broken inversion symmetry and time reversal symmetry. First-principles investigations reveal that the magnitude of the valley splitting in magnetic VSe2 induced by spin-orbit coupling reaches as high as 78.2 meV and can be linearly tuned by biaxial strain. Besides conventional polarized light, hole doping or illumination with light of proper frequency can offer effective routes to realize valley polarization. Moreover, spin-orbit coupling in monolayer VSe2 breaks not only the valley degeneracy but also the three-fold rotational symmetry in band structure. The intrinsic and tunable valley splitting and the breaking of optical isotropy bring additional benefits to valleytronic and optoelectronic applications.

2.
J Insect Sci ; 14: 187, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25480973

RESUMO

The western flower thrips, Frankliniella occidentalis (Pergande), and the sweetpotato whitefly, Bemisia tabaci (Gennadius), are both invasive insect pests and are present in most of the same agricultural crops without a clear dominance of either species. Here, intra- and interspecific competition in B. tabaci and F. occidentalis was determined under controlled experiments. The results showed that intraspecific competition was distinct in F. occidentalis and that the co-occurrence of B. tabaci had a strong effect on F. occidentalis, resulting in a decrease in oviposition. Significant intraspecific competition was found in B. tabaci, and the coexistence of F. occidentalis had limited effect on the oviposition of B. tabaci. In a selective host plant preference experiment, both F. occidentalis and B. tabaci preferred eggplants most, followed by cucumbers and tomatoes. On cucumber plants, B. tabaci was predominant, whereas on eggplant and tomato plants, F. occidentalis and B. tabaci exhibited comparative competitive abilities during the initial stage. However, over time, higher numbers of B. tabaci than that of F. occidentalis were found on the two host plants. Our in vitro and potted plant experiments indicate that B. tabaci is competitively superior to F. occidentalis, which might help to explain their differential distribution patterns in China.


Assuntos
Hemípteros/fisiologia , Tisanópteros/fisiologia , Animais , Comportamento Competitivo , Comportamento Alimentar , Feminino , Fertilidade , Cadeia Alimentar , Masculino , Oviposição , Densidade Demográfica , Especificidade da Espécie
3.
Biomaterials ; 35(18): 5028-38, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24680191

RESUMO

A somatostatin analog, vapreotide (VAP), can be used as a ligand for targeting drug delivery based on its high affinity to somatostatin receptors (SSTRs), which is overexpressed in many tumor cells. RNA interference plays an important role on downregulation of vascular endothelial growth factor (VEGF), which is important for tumor growth, progression and metastasis. To improve tumor therapy efficacy, the vapreotide-modified core-shell type nanoparticles co-encapsulating VEGF targeted siRNA (siVEGF) and paclitaxel (PTX), termed as VAP-PLPC/siRNA NPs, were developed in this study. When targeted via somatostatin receptors to tumor cells, the VAP-PLPC/siRNA NPs could simultaneously delivery siVEGF and PTX into cells and achieve a synergistic inhibition of tumor growth. Interestingly, in vitro cell uptake and gene silencing experiments demonstrated that the targeted VAP-PLPC/siRNA NPs exhibited significant higher intracellular siRNA accumulation and VEGF downregulation in human breast cancer MCF-7 cells, compared to those of the non-targeted PEG-PLPC/siRNA NPs. More importantly, in vivo results further demonstrated that the targeted VAP-PLPC/siRNA NPs had significant stronger drug distribution in tumor tissues and tumor growth inhibition efficacy via receptor-mediated targeting delivery, accompany with an obvious inhibition of neovascularization induced by siVEGF silencing. These results suggested that the co-delivery of siRNA and paclitaxel via vapreotide-modified core-shell nanoparticles would be a promising approach for tumor targeted therapy.


Assuntos
Antineoplásicos Fitogênicos/farmacologia , Terapia de Alvo Molecular , Nanopartículas/química , Paclitaxel/farmacologia , RNA Interferente Pequeno/genética , Somatostatina/análogos & derivados , Fator A de Crescimento do Endotélio Vascular/genética , Animais , Neoplasias da Mama/terapia , Ciclo Celular/efeitos dos fármacos , Regulação para Baixo , Sistemas de Liberação de Medicamentos , Feminino , Humanos , Células MCF-7 , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptores de Somatostatina/metabolismo , Somatostatina/farmacologia , Fator A de Crescimento do Endotélio Vascular/metabolismo
4.
Biomaterials ; 34(21): 5303-16, 2013 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-23570718

RESUMO

In this study, a series of bioreducible poly(amidoamine)s grafting different percentages of cholesterol (rPAA-Ch14: 14%, rPAA-Ch29: 29%, rPAA-Ch57: 57% and rPAA-Ch87: 87%) was synthesized and used for siRNA delivery. These amphiphilic polymers were able to self-assemble into cationic nanoparticles in aqueous solution at low concentrations. The nanoparticle formation was evidenced via cryo-transmission electron microscope (Cryo-TEM) and dynamic light scattering analysis. The average hydrodynamic size of rPAA-Ch blank nanoparticles was about 80-160 nm with zeta potential of 50-60 mV. Also, the effects of different percentages of cholesterol grafted onto rPAA on physicochemical characteristics, in vitro cytotoxicity, cellular uptake, VEGF gene silencing efficacy and translocation mechanism of rPAA-Ch/siRNA complexes were investigated. The results showed that rPAA-Ch57 polymer was not only able to form stable nanocomplexes and possess high cell uptake, but also to exhibit the best in vitro VEGF gene silencing efficacy and the best in vivo tumor growth inhibition effect when it was formulated with VEGF-siRNA. Moreover, the observations of confocal laser scanning microscope (CLSM) and the study of cholesterol competitive inhibition demonstrated that endosomal/lysosomal escape and cytoplasmic dissociation of rPAA-Ch57/siRNA complexes were dependent on the "proton sponge effect" and disulfide cleavage, following internalization with cholesterol-related endocytosis pathway and subsequent transportion into endosomes/lysosomes. These findings indicated that the rPAA-Ch57 polymer should be a promising and potent carrier for siRNA delivery.


Assuntos
Colesterol/química , Técnicas de Transferência de Genes , Nanopartículas/química , Poliaminas/química , RNA Interferente Pequeno/metabolismo , Animais , Cátions , Proliferação de Células , Endocitose , Endossomos/metabolismo , Feminino , Inativação Gênica , Humanos , Espaço Intracelular/metabolismo , Lisossomos/metabolismo , Células MCF-7 , Espectroscopia de Ressonância Magnética , Camundongos , Camundongos Nus , Nanopartículas/ultraestrutura , Oxirredução , Tamanho da Partícula , Poliaminas/síntese química , Polietilenoimina/química , Fator A de Crescimento do Endotélio Vascular/genética
6.
Biomaterials ; 33(28): 6793-807, 2012 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-22721724

RESUMO

Due to the absence of safe and effective carriers for in vivo delivery, the applications of small interference RNA (siRNA) in clinic for therapeutic purposes have been limited. In this study, a biodegradable amphiphilic tri-block copolymer (mPEG(2000)-PLA(3000)-b-R(15)) composed of monomethoxy poly(ethylene glycol), poly(d,l-lactide) and polyarginine was synthesized and further self-assembled to cationic polymeric nanomicelles for in vivo siRNA delivery, with an average diameter of 54.30 ± 3.48 nm and a zeta potential of approximately 34.8 ± 1.77 mV. The chemical structures of the copolymers were well characterized by (1)H NMR spectroscopy and FT-IR spectra. In vitro cytotoxicity and hemolysis assays demonstrated that the polymeric nanomicelles showed greater cell viability and haemocompatibility than those of polyethyleneimine (PEI) or R(15) peptide. In vitro experiments demonstrated that EGFR targeted siRNA formulated in micelleplexes exhibited approximately 65% inhibition of EGFR expression on MCF-7 cells in a sequence-specific manner, which was comparable to Lipofectamine™ 2000. The results of intravenous administration showed Micelleplex/EGFR-siRNA significantly inhibited tumor growth in nude mice xenografted MCF-7 tumors, with a remarkable inhibition of EGFR expression. Furthermore, no positive activation of the innate immune responses and no significant body weight loss was observed during treatment suggested that this polymeric micelle delivery system is non-toxic. In conclusion, the present nanomicelles based on cationic mPEG(2000)-PLA(3000)-b-R(15) copolymer would be a safe and efficient nanocarrier for in vivo delivery of therapeutic siRNA.


Assuntos
Nanopartículas/administração & dosagem , Neoplasias/tratamento farmacológico , Peptídeos/administração & dosagem , Poliésteres/administração & dosagem , RNA Interferente Pequeno/administração & dosagem , Análise de Variância , Animais , Feminino , Humanos , Células MCF-7 , Espectroscopia de Ressonância Magnética , Camundongos , Camundongos Endogâmicos BALB C , Micelas , Nanopartículas/química , Tamanho da Partícula , Peptídeos/química , Poliésteres/química , Polietilenoglicóis/administração & dosagem , Polietilenoglicóis/química , Espectroscopia de Infravermelho com Transformada de Fourier
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