180,755 research outputs found
Simple Modifications of Branched PEI Lead to Highly Efficient siRNA Carriers with Low Toxicity
No full textPolymer carriers like PEI which proved their efficiency in DNA delivery were found to be far less effective for the applications with siRNA. In the current study, we generated a number of nontoxic derivates of branched PEI through modification of amines by ethyl acrylate, acetylation of primary amines, or introduction of negatively charged propionic acid or succinic acid groups to the polymer structure. The resulting products showed high efficiency in siRNA-mediated knockdown of target gene. In particular, succinylation of branched PEI resulted in up to 10-fold lower polymer toxicity in comparison to unmodified PEI. Formulations of siRNA with succinylated PEI were able to induce remarkable knockdown (80% relative to untreated cells) of target luciferase gene at the lowest tested siRNA concentration of 50 nM in Neuro2ALuc cells. The polyplex stability assay revealed that the efficiency of formulations which are stable in physiological saline is independent of the affinity of siRNA to the polymer chain. The improved properties of modified PEI as siRNA carrier are largely a consequence of the lower polymer toxicity. In order to achieve significant knockdown of target gene, the PEI-based polymer has to be applied at higher concentrations, required most probably for sufficient accumulation and proton sponge effects in endosomes. Unmodified PEI is highly toxic at such polymer concentrations. In contrast, the far less toxic modified analogues can be applied in concentrations required for the knockdown of target genes without side effects
Experimental investigations on core drilling by ultrasonic-vibration-assisted grinding for hard-to-machine materials - A review
No full textCitation: Qin, N., Lei, J., & Pei, Z. J. (2016). Experimental investigations on core drilling by ultrasonic-vibration-assisted grinding for hard-to-machine materials - A review. International Journal of Manufacturing Research, 11(1), 28-52. doi:10.1504/IJMR.2016.076976Ultrasonic-vibration-assisted grinding (UVAG), a hybrid machining process combining material removal mechanisms of diamond grinding and ultrasonic machining, has been used to machine various hard-to-machine materials. Large amount of research work on UVAG has been carried out since it is invented. However there are few review papers to cover the current literature on UVAG. The emphasis of this literature review is the experimental investigations of the drilling process with ultrasonic vibration using a core drill with metal-bonded diamond abrasives. Experimental results are summarised and compared. The inconsistent results and their reasons are discussed. Furthermore, directions of future research on UVAG are also presented. © 2016 Inderscience Enterprises Ltd
Differential intracellular distribution of DNA complexed with polyethylenimine (PEI) and PEI-polyarginine PTD influences exogenous gene expression within live COS-7 cells-2
No full text<p><b>Copyright information:</b></p><p>Taken from "Differential intracellular distribution of DNA complexed with polyethylenimine (PEI) and PEI-polyarginine PTD influences exogenous gene expression within live COS-7 cells"</p><p>http://www.gvt-journal.com/content/5/1/11</p><p>Genetic Vaccines and Therapy 2007;5():11-11.</p><p>Published online 26 Nov 2007</p><p>PMCID:PMC2211466.</p><p></p>us stained with DAPI (B, E) and merged immunofluorescence displayed as (C, F). Distribution of PEI/pDNA-YOYO in untreated (G) and nocodazole treated (J) cells with MitoTracker staining (H, K). Merge MitoTracker and PEI/pDNA-YOYO in untreated (I) and nocodazole treated (L) cells. Scale bar = 10 μm. Images represent typical result of two individual slides viewed for each sample, analyzed 5 h post transfection
Bio-inspired PEI/BNNS composite film via hydrogen bond self-assembly for efficiently enhancing high-temperature dielectric energy storage
No full textPolymer-based film capacitors are in high demand for modern electronic and electrical applications, but it is still challengeable to optimize their high-temperature energy storage capability. Herein, inspired by the regular alignment of fish scales, polyetherimide/BN nanosheets (PEI/BNNS) films with similar morphology were designed via hydrogen bond self-assembly process. The results indicated that the BNNS inorganic layer played important roles on suppressing carrier transport and reducing conduction loss, resulting in simultaneous improvements on dielectric and breakdown properties as well as energy storage performances. At room temperature, the highest energy density (Ue) of PEI/BNNS samples (PEI-BN4) achieved to 8.50 J cm−3 with charge/discharge efficiency (η) of 90.2 %, which increased by 77.1 % compared to the Ue of neat PEI. At 200 °C, PEI-BN4 also exhibited the highest Ue of 4.46 J cm−3 with η of 91.3 %, which was 94.8 % higher than neat PEI film (Ue = 2.29 J cm−3 with the η of 87.8 %). To the best of our knowledge, the energy storage performances of PEI-BN4 were better than most of currently reported high-temperature PEI-based dielectric films. The current work proposes a novel surface engineering strategy to design high-performance polymer composite film, and promote the applications of new generation of high-temperature resistant electronic devices
[Report to Chief J. E. Curry, by an unknown author #1]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
[Report to Chief J. E. Curry, by an unknown author #2]
No full textReport to Chief J. E. Curry, by an unknown author. The report contains a list of officers who gave depositions to the United States Attorney
Síntese de polietilenoiminas ramificadas decoradas com grupos hidrofóbicos e nucleosídeos e estudos de sua interação com dodecilsulfato de sódio e DNA
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciencias Fisicas e Matematicas, Programa de Pós-Graduação em Química, Florianópolis, 2012A poli(etilenoimina) (PEI) foi modificada por meio da alquilação com grupos n-alquila (n = 4, 6, 8 e 12 carbonos). O espalhamento de raios X a baixos ângulos (SAXS), tensão superficial, emissão de fluorescência do pireno, viscosidade e medidas de pH foram as técnicas usadas para investigar a conformação e agregação das PEIs hidrofobicamente modificadas em solução aquosa, na ausência e na presença de dodecil sulfato de sódio (SDS). Medidas de SAXS mostraram que o raio de giro diminui com o aumento do comprimento da cadeia alquílica, enquanto que os dados de viscosidade indicaram uma diminuição na viscosidade intrínseca. A PEI não modificada não apresentou atividade na superfície, enquanto as PEIs modificadas mostraram atividade pronunciada na superfície e presença de domínios hidrofóbicos. Na presença de SDS, o início da formação do complexo polímero-surfactante foi determinado, indicando uma diminuição na concentração de agregação crítica (cac) com o aumento no comprimento da cadeia alquílica substituída na PEI. A PEI também foi decorada com o grupo uridina com dois graus de substituição (5% e 15%). A formação de complexos das PEIs, decoradas com uridina ou hidrofobicamente modificadas, com o DNA do timo de bezerro foi investigada através das técnicas de emissão de fluorescência do brometo de etídio, espectrofotometria de UV-Vis, dicroísmo circular (CD), potencial zeta, viscosidade, espalhamento de luz dinâmico (DLS) e SAXS, na ausência e na presença de SDS. Todas as PEIs apresentaram três etapas na formação de complexos com o DNA: a primeira, quando uma pequena quantidade de polieletrólito foi adicionada, as cadeias do DNA são parcialmente condensadas; a segunda, quando mais polieletrólito foi adicionado, apresenta complexos com densidade de carga nula, com tamanho micrométrico; a terceira, em concentrações mais altas da PEI, o DNA foi completamente condensado pelas cadeias das PEIs, formando complexos positivamente carregados com valores de RH,ap na faixa de 51 a 88 nm. Análises de viscosidade e SAXS sugerem que o a PEI não modificada teve a interação mais forte e que melhor condensa o DNA.Abstract : The polyethylene imine (PEI) was modified by means of the alkylation with n-alkyl groups (n = 4, 6, 8 and 12 carbons). Small-angle X-ray scattering (SAXS), viscosity, surface tension, and pyrene fluorescence emission were then used as techniques to examine the conformation and aggregation of the hydrophobically modified PEIs in aqueous solution, in the absence and presence of sodium dodecylsulfate (SDS). Analysis of the SAXS data showed that the radius of gyration decreases with an increase in the alkyl chain length of the polymer, while the viscosity data indicated a decrease in the intrinsic viscosity under the same conditions. The nonmodified PEI was not surface active, while the hydrophobically modified samples showed pronounced surface activity and the presence of hydrophobic domains. On addition of SDS, the onset of the formation of polymer#surfactant complexes was determined, indicating a decrease in the critical aggregate concentration (cac) with an increase in the alkyl chain length of the polymer backbone. The PEI also was decorated with uridine groups with two substitution degrees (5% and 15%). The complex formation of the decorated or hydrophobically modified PEI with calf thymus DNA was investigated through of the ethidium bromide fluorescence emission, UV-Vis spectrophotometry, circular dichroism (CD), potential zeta, viscosity, dynamic light scattering (DLS) and SAXS techniques, in the absence and presence of SDS. All versions of PEI showed three steps in complexes formation with DNA: first, when a small amount of polyelectrolyte was added, DNA chains were partially condensed; second, when more polyelectrolyte was added, the complexes had a null charge density and micrometric size; third, at higher concentration of PEI, the DNA was fully condensed by PEI chains, leading to positively charged complexes with RH,ap values in the range of 51-88 nm. Viscosity and SAXS analyses suggested that the unmodified PEI had the stronger interaction and promoted the best DNA condensation
Estudo da aplicação do pei hidrofobicamente modificado como agente de estabilização de emulsões do tipo óleo em água
No full textTCC (graduação) - Universidade Federal de Santa Catarina. Centro de Ciências Físicas e Matemáticas. Curso de Química.Uma emulsão é um sistema heterogêneo disperso em que as fases são líquidos imiscíveis ou parcialmente miscíveis. A aplicação prática de emulsões é considerável, e inclui produtos alimentares, preparações farmacêuticas, cosméticos, entre outros. Para preparar emulsões estáveis, um terceiro componente - um agente emulsificador (ou emulsificante) - precisa estar presente. As funções de um agente emulsificador são facilitar a emulsão e promover a estabilidade da emulsão. O agente emulsificador forma um filme adsorvido sobre as gotas dispersas que ajuda a prevenir coagulação e coalescência, estabilizando as emulsões através de dois possíveis mecanismos: estabilização elétrica e estérea. Neste trabalho, utilizamos como agente estabilizador de emulsões do tipo óleo em água um polieletrólito positivamente carregado: desta maneira, ambos os mecanismos de estabilização elétrica e estérica estarão presentes. O polímero é o PEI hidrofobicamente modificado, o poli(etilenoimina) N - dodecilado (PEI-DoD). O PEI derivado mostrou-se eficiente na preparação de emulsões, demonstrando um valor médio de tamanho das gotículas em torno de 150 nm. A presença de lecitina nas emulsões diminuiu o tamanho das gotículas como também as tornaram menos polidispersas. O potencial zeta medido nas partículas, em torno de 65-70 mV, é um valor considerado ótimo para manter as emulsões estáveis. A presença de lecitina nas formulações tornou o valor levemente superior, contribuindo também para a estabilidade das emulsões. Podemos concluir, assim, que as emulsões estudadas utilizando PEI-DoD se mostraram estáveis e o polímero hidrofobicamente modificada eficiente como agente estabilizante de emulsões do tipo O/A
Aerosolized BC-819 inhibits primary but not secondary lung cancer growth.
No full textDespite numerous efforts, drug based treatments for patients suffering from lung cancer remains poor. As a promising alternative, we investigated the therapeutic potential of BC-819 for the treatment of lung cancer in mouse tumor models. BC-819 is a novel plasmid DNA which encodes for the A-fragment of Diphtheria toxin and has previously been shown to successfully inhibit tumor growth in human clinical study of bladder carcinoma. In a first set of experiments, we examined in vitro efficacy of BC-819 in human lung cancer cell-lines NCI-H460, NCI-H358 and A549, which revealed >90% reduction of cell growth. In vivo efficacy was examined in an orthotopic mouse xenograft lung cancer model and in a lung metastasis model using luminescent A549-C8-luc adenocarcinoma cells. These cells resulted in peri- and intra-bronchiolar tumors upon intrabronchial application and parenchymal tumors upon intravenous injection, respectively. Mice suffering from these lung tumors were treated with BC-819, complexed to branched polyethylenimine (PEI) and aerosolized to the mice once per week for a period of 10 weeks. Using this regimen, growth of intrabronchially induced lung tumors was significantly inhibited (p = 0.01), whereas no effect could be observed in mice suffering from lung metastasis. In summary, we suggest that aerosolized PEI/BC-819 is capable of reducing growth only in tumors arising from the luminal part of the airways and are therefore directly accessible for inhaled BC-819
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