Este trabalho foi financiado pela NSF / DOE Parceria em Plasma Ciência e Tecnologia (NSF Grant No. CBET-0853777 e DOE Grant No. DE-SC0001169), a Fase I do projeto STTR (NSF STTR FASE I No.1010133). Os autores gostariam de agradecer ao Programa de Pesquisa PPPL Offsite apoiado pelo Escritório do Fusion Energy Sciences para apoiar experiências de arco.

1. Preparação do ânodo <ol><li> Pó de níquel escala (99,8%, a 300 mesh) e ítrio em pó (99,9%, 40 mesh) de acordo com a rádio molar de 4.2:1 como o pó de catalisador. </li><li> Misture o pó catalisador com pó de grafite (99,9995%, a 200 mesh) muito bem. Preencha o pó misturado em bastão de grafite oca (5 mm de diâmetro externo, 2,5 mm de diâmetro interno e 75 mm de comprimento) com firmeza. Certifique-se o rádio totais molar de C: Ni: Y no ânodo é 94.8:4.2:1, que é óptima relação de sintetizar SWCNT 9. </li><li> Instale catodo haste (grafite puro, 13 mm de diâmetro) eo ânodo de pelúcia dentro de câmara cilíndrica (aço inoxidável, 152 mm de diâmetro e 254 mm de comprimento). Ajustar a distância lacuna entre o cátodo eo ânodo de cerca de 3 mm. </li></ol> 2. Configuração do substrato <ol><li> Coloque um ímã permanente cubóide (25 mm × 25 mm × 100 mm) no interior da câmara em cerca de 25 mm de distância do eixo intereletrodos. O Ultra-High-Temp ímã Alnico usadosNo experimento tem o peso de 650 gramas. Use a configuração quando o gap intereletrodos é colocado a uma distância de cerca de h = 75 mm (Figura 1a) do fundo do imã permanente. </li><li> Corte a folha de 0,3 milímetros de espessura de molibdênio (99,95%) como o de 25 mm × 100 mm forma retangular. Eliminar a contaminação da superfície por dismembrator ultra-som em acetona e etanol, durante 30 min com 50% da amplitude da sonicando, 150 w de potência de saída e 40 kHz. </li><li> Instale folha de molibdênio anexando um lado do ímã permanente, e virar deste lado para eletrodos. </li><li> Medir o campo magnético no gap intereletrodos por um gaussmeter. Manter o campo magnético médio entre os eletrodos é de cerca de 0,06 T. </li></ol> 3. Ignição de arco de plasma <ol><li> Bomba de baixo da câmara cilíndrica à pressão inferior a 10 -1 a vácuo Torr e depois encheu-o com hélio (99,995%) a 500 Torr. </li><li> Conectar eletrodos arco para DC welding fonte de alimentação e configurar o fornecimento de energia em corrente de arco de cerca de 75 A. </li><li> Registre os valores em tempo real da tensão do arco do arco atual, e pressão da câmara de pós-experiência de análise. </li><li> Iniciar o vídeo do arco da viewports direita e frontal por duas câmeras digitais simultaneamente. Os instantâneos após 1 segundo de arco de partida são mostrados na Figura 1b (de viewport direita) e Figura 1d (de frente viewport). </li><li> Execute o arco para 15 segundos. Arrefecer câmara por convecção natural durante pelo menos 20 minutos. </li></ol> 4. Pós-síntese de análise e caracterização <ol><li> Use uma pinça para arrancar o floco de deposição a partir da superfície da folha de molibdênio, onde o arco jet plasmas foi dirigido. Outra amostra é coletada do colarinho preto de catodo. Observar a morfologia de ambos os lados do floco de deposição em SEM (tensão de aceleração de 30 KV foi usado). </li><li> Em relação à preparação de amostras para<html> TEM análise, os filmes finos de amostra foram obtidos por queda de fundição uma suspensão de solução de metanol dispersos SWCNT após sonicando por 60 minutos, utilizando dismembrator ultra-som com 50% sonicando amplitude. Observar a morfologia do filme fino sob TEM JEOL com a tensão de 100 KV após a volatilização de solução de metanol. Para o cargo de interesse na amostra, o padrão de difração de elétrons podem ser obtidas com o comprimento da câmara CCD de 50 cm associada a TEM. </li><li> A espectroscopia Raman foi realizada em um sistema micro-Raman baseado em um 200 mW Lexel 3000 Ar ion laser (saída de linha única sintonizável), com óptica holográfica, um espectrômetro de 0,5 m e um de nitrogênio líquido refrigerado detector CCD; 514 nm, que corresponde à de energia de 2,33 eV. Medidas Raman cobriu a faixa de 100 cm -1 a 3100 cm -1, e foram realizadas na superfície de flocos de grafeno. </li></ol> 5. Resultados representante &quot;&gt; Os instantâneos de vídeo obtida simultaneamente a partir de viewports direita e frontal da câmara são mostrados na Figura 1b, d para h = 75 mm. Estas imagens ilustram perturbação significativa da coluna do arco plasma na presença de campo magnético externo, em comparação com a coluna de arco axialmente simétrica observado no caso sem um campo magnético 10. Figura 2a e 2b mostrar a morfologia típica de SWCNT e catalisador partículas coletadas na gola de catodo sem campo magnético e com o campo magnético de B = 0,06 Tesla sob TEM, respectivamente. Pode ser visto que SWCNT com o campo magnético são close-embalados em pacotes com diâmetros variando de 2 a 20 nm, devido à interação de van der Waals entre SWCNT individual. Em comparação, o campo magnético SWCNT sem ter o diâmetro maior em feixes e de maior diâmetro individual, o que é consistente com a análise do espectro de Raman. Além disso, o campo magnético can resultar na SWCNT com maior pureza mostrado na Figura 2a e 2b. A influência mais interessante do campo magnético é que flocos de grafeno pode ser obtido a partir da superfície de flocos de deposição que está perto de folha de molibdênio no mesmo processo. Figura 2c e 2d mostram as imagens SEM e TEM de flocos de grafeno, bem como alguns- grafeno camada obtidos a partir da amostra colhida no local correspondeu a jatos de plasmas de arco. A inserção da Figura 2d mostra o padrão de difração de elétrons associados com o grafeno. O padrão hexagonal pontos de difração de elétrons apresenta as evidências de estruturas bem ordenadas de cristal. Espectro Raman é uma ferramenta poderosa para a caracterização de grafeno flocos e SWCNT. Os picos típicos observados em grafeno são os picos G e 2D em ~ 1600 cm -1 e ~ 2700 centímetros -1, respectivamente, usando o comprimento de onda de excitação de 514 nm. O Gpico tem origem nas vibrações de avião que pode ser observado em todos os materiais de carbono sp2. O pico 2D é uma segunda ordem do pico D, mas é visto até mesmo em sistemas não desordenado, devido à ordem phonon quarto processo de dinâmica de troca de ressonância dupla. Ela desempenha um papel crucial na caracterização de grafeno. A intensidade I (2D) / I (G) é de aproximadamente 4 para o grafeno monocamada e diminui com a adição de camadas subsequentes, tornando assim possível estimar a espessura das camadas de grafeno. 11 Figura 3 indica que o valor de I (2D) / I (G) é de cerca de 1, que pode ser a evidência de algumas camadas de grafeno. O modo de respiração radial (RBM) entre 120 e 350 cm -1 no espectro Raman pode ser usada para identificar o diâmetro de nanotubos através da frequência de vibração coerente dos átomos C na direção radial. A relação experimental entre a freqüência e diâmetro SWCNT é RBM ω = A / t d + B, onde os parâmetros of A e B igual a 234 e 10 cm -1, respectivamente, para o SWCNT típico formado em feixes. Na Figura 3, as freqüências de RBM SWCNT sem e com campo magnético são 163,8 e 215,2 cm -1, correspondente à média diâmetros SWCNT individuais de 1,52 e 1,14 nm, respectivamente. <img alt="Figura 1." src="/files/ftp_upload/3455/3455fig1.jpg" /> Figura 1. Distribuição do campo magnético simulado por software FEMM 4.2 (a), fotografia de jet arco plasmas da viewport direita (b), diagrama esquemático de eletrodos de posição e de campo magnético em direção a lacuna para o caso quando o gap intereletrodos está posicionado cerca de 75 mm acima do fundo do imã permanente (c), e uma fotografia do jet arco plasmas da viewport front (d). <img alt="Figura 2." src="/files/ftp_upload/3455/3455fig2.jpg" /> Figura 2. Representante da imagem TEM como sintetizadosFeixes SWCNT sem campo magnético (a) e feixes SWCNT com o campo magnético (b), imagem SEM típicas de flocos de grafeno sintetizado com o campo magnético (c), e da imagem TEM de grafeno com o campo magnético. Inset é a área selecionada padrão de difração de elétrons mostrando a estrutura cristalina de grafeno. <img alt="Figura 3." src="/files/ftp_upload/3455/3455fig3.jpg" /> Figura 3. Espectro Raman das amostras com o campo magnético na faixa de 100-3100 cm -1. Detalhe: o espectro Raman das amostras sem campo magnético ao redor freqüências RBM. <img alt="Figura 4." src="/files/ftp_upload/3455/3455fig4.jpg" /> Figura 4. Nanoestrutura região de crescimento e densidade número de carbono e níquel para arco de 60 A. Note que as densidades de carbono e níquel mostrado no lado esquerdo e direito dos eletrodos, co-existem na mesma região.

<ol>
	<li>Dai, H. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrical+transport+properties+and+field+effect+transistors+of+carbon+nanotubes.">Electrical transport properties and field effect transistors of carbon nanotubes.</a> Nano. 1, 1-13 (2006).</li><li>Lai, K. W. C., Xi, N., Fung, C. K. M., Chen, H. Z., Tarn, T. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Engineering+the+band+gap+of+carbon+nanotube+for+infrared+sensors.">Engineering the band gap of carbon nanotube for infrared sensors.</a> Applied Physics Letters. 95, 221107-221107 (2009).</li><li>Gabor, N. M., Zhong, Z. H., Bosnick, K., Park, J., McEuen, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Extremely+Efficient+Multiple+Electron-Hole+Pair+Generation+in+Carbon+Nanotube+Photodiodes.">Extremely Efficient Multiple Electron-Hole Pair Generation in Carbon Nanotube Photodiodes.</a> Science. 325, 1367-1371 (2009).</li><li>Liu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hydrogen+storage+in+single-walled+carbon+nanotubes+at+room+temperature.">Hydrogen storage in single-walled carbon nanotubes at room temperature.</a> Science. 286, 1127-1129 (1999).</li><li>Keidar, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Magnetic-field-enhanced+synthesis+of+single-wall+carbon+nanotubes+in+arc+discharge.">Magnetic-field-enhanced synthesis of single-wall carbon nanotubes in arc discharge.</a> Journal of Applied Physics. 103, 094318-094318 (2008).</li><li>Li, J., Volotskova, O., Shashurin, A., Keidar, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Controlling+Diameter+Distribution+of+Catalyst+Nanoparticles+in+Arc+Discharge.">Controlling Diameter Distribution of Catalyst Nanoparticles in Arc Discharge.</a> Journal of Nanoscience and Nanotechnology. 11, 10047-10052 (2011).</li><li>Volotskova, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Tailored+Distribution+of+Single-Wall+Carbon+Nanotubes+from+Arc+Plasma+Synthesis+Using+Magnetic+Fields.">Tailored Distribution of Single-Wall Carbon Nanotubes from Arc Plasma Synthesis Using Magnetic Fields.</a> Acs. Nano. 4, 5187-5192 (2010).</li><li>Volotskova, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-step+synthesis+and+magnetic+separation+of+graphene+and+carbon+nanotubes+in+arc+discharge+plasmas.">Single-step synthesis and magnetic separation of graphene and carbon nanotubes in arc discharge plasmas.</a> Nanoscale. 2, 2281-2285 (2010).</li><li>Farhat, S., Scott, C. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Review+of+the+arc+process+modeling+for+fullerene+and+nanotube+production.">Review of the arc process modeling for fullerene and nanotube production.</a> Journal of Nanoscience and Nanotechnology. 6, 1189-1210 (2006).</li><li>Keidar, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Increasing+the+length+of+single-wall+carbon+nanotubes+in+a+magnetically+enhanced+arc+discharge.">Increasing the length of single-wall carbon nanotubes in a magnetically enhanced arc discharge.</a> Applied Physics Letters. 92, 043129-043129 (2008).</li><li>Ferrari, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raman+spectrum+of+graphene+and+graphene+layers.">Raman spectrum of graphene and graphene layers.</a> Physical Review Letters. 97, 187401-187401 (2006).</li></ol>

Não temos nada a revelar.

Nos instantâneos de vídeo mostrado na figura 1b e 1d, para o caso que a diferença intereletrodos foi colocado a uma distância de cerca de h = 75 mm da base de ímã permanente, deve-se notar que a mudança de posição do ímã (que testamos mudança ímã ao longo eixo z e girando o ímã sobre) resulta em desvio do fluxo de jacto de arco eléctrico na direção x correspondente à direção de J × B força ilustrada na Figura 1c. Também foi observado que a geome...

Tabela de reagentes e equipamentos específicos: <table border="1"><tbody><tr><th> Nome do reagente </th><th> Companhia </th><th> Número de catálogo </th><th> Comments (opcional) </th></tr><tr><td> Metanol </td><td> Acros Organics </td><td> 423950010 </td><td></td></tr><tr><td> Pó de níquel </td><td> Alfa Aesar </td><td> 10581 </td><td></td></tr><tr><td> Ítrio pó </td><td> Acros Organics </td><td> 318060050 </td><td></td></tr><tr><td> Pó de grafite </td><td> Alfa Aesar </td><td> 40799 </td><td></td></tr><tr><td> Bastão de grafite oco </td><td> Saturno Industries </td><td> POCO EDM 3 </td><td></td></tr><tr><td> Ímã permanente </td><td> McMaster-Carr </td><td> 57315K51 </td><td></td></tr><tr><td> Folha de molibdênio </td><td> Dingqi Sci. e Tech. </td><td> 080504-11 </td><td></td&gt; </tr><tr><td> Ultra-som dismembrator </td><td> Fisher Scientific </td><td> Modelo 150T </td><td></td></tr><tr><td> De efeito Hall gaussmeter </td><td> AI </td><td> Modelo 100 </td><td></td></tr><tr><td> Fornecimento de energia de soldagem </td><td> Miller Elétrica </td><td> Gold Star 600SS </td><td></td></tr><tr><td> Bomba de vácuo </td><td> J / B </td><td> DV-85N </td><td></td></tr><tr><td> SEM </td><td> Zeiss </td><td> LEO 1430VP </td><td></td></tr><tr><td> TEM </td><td> JEOL </td><td> 1200 EX </td><td></td></tr><tr><td> Raman </td><td> Horiba </td><td> HR800 </td><td></td></tr></tbody></table>

simultaneous synthesis of single-walled carbon nanotubes and graphene in a magnetically-enhanced arc plasma

Nanoestruturas de carbono, como nanotubos de carbono de parede única (SWCNT) e grafeno atrair um dilúvio de interesse dos estudiosos hoje em dia, devido à sua aplicação muito promissora para sensores molecular, transistor de efeito de campo e super fino e flexível dispositivos eletrônicos 1-4. Descarga de arco anódica apoiado pela erosão do ânodo é um dos métodos mais práticos e eficientes, o que pode fornecer específicos não-equilíbrio processos e um fluxo elevado de material de carbono para o desenvolvimento de estruturas em temperatura relativamente mais altos e, conseqüentemente, o as- produtos sintetizados têm poucos defeitos estruturais e melhor cristalinidade. Para melhorar ainda mais a controlabilidade e flexibilidade da síntese de nanoestruturas de carbono na descarga de arco, os campos magnéticos podem ser aplicados durante o processo de síntese de acordo com as respostas magnético forte de plasmas de arco. Foi demonstrado que o magneticamente avançada arco Discharge pode aumentar a duração média de SWCNT 5, estreita a distribuição de diâmetro de partículas de catalisador metálico e nanotubos de carbono 6, e alterar a relação de materiais metálicos e nanotubos de carbono semicondutores 7, bem como levar à síntese de grafeno 8. Além disso, vale a pena observar que quando introduzimos um campo magnético não uniforme com o componente normal para a corrente em arco, a força de Lorentz ao longo da direção J × B pode gerar o jet plasmas e fazer a entrega efetiva de partículas de carbono e de íons fluxo de calor para amostras. Como resultado, flocos em larga escala de grafeno e nanotubos de carbono de alta pureza single-walled foram simultaneamente gerados por tal método novo arco magneticamente avançada anódica. Arc de imagem, microscópio eletrônico de varredura (SEM), microscopia eletrônica de transmissão (TEM) e espectroscopia Raman foram empregadas para analisar a caracterização de nanoestruturas de carbono. Estes resultados indicam umaamplo espectro de oportunidades para manipular com as propriedades de nanoestruturas produzidas em plasmas por meio de controlar as condições de arco.

Watch this Scientific Journal Video about Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma at JoVE.com

Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Descarga de arco anódica é um dos métodos mais práticos e eficientes para sintetizar nanoestruturas de carbono diversos. Para aumentar a controlabilidade de arco e flexibilidade, um campo magnético não uniforme foi apresentado ao processo de síntese de uma etapa de flocos em larga escala de grafeno e nanotubos de carbono de alta pureza single-walled.

Síntese simultânea de nanotubos de carbono de parede única e de grafeno em um Plasma Arc magnética avançada

Carbon nanostructures such as single-walled carbon nanotubes (SWCNT) and graphene attract a deluge of interest of scholars nowadays due to their very ...

simultaneous-synthesis-single-walled-carbon-nanotubes-graphene

Research

JoVE Journal

Bioengineering

15.2K visualizações.  The George Washington University. Descarga de arco anódica é um dos métodos mais práticos e eficientes para sintetizar nanoestruturas de carbono diversos. Para aumentar a controlabilidade de arco e flexibilidade, um campo magnético não uniforme foi apresentado ao processo de síntese de uma etapa de flocos em larga escala de grafeno e nanotubos de carbono de alta pureza single-walled.

Vídeo: Simultaneous Synthesis of Single-walled Carbon Nanotubes and Graphene in a Magnetically-enhanced Arc Plasma

Graphene Coatings for Biomedical Implants

Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with nanometer thick layers of graphene for applications as a stent material. Graphene was grown on copper substrates via chemical vapor deposition and then transferred onto nitinol substrates. In order to understand how the graphene coating could change biological response, cell viability of rat aortic endothelial cells and rat aortic smooth muscle cells was investigated. Moreover, the effect of graphene-coatings on cell adhesion and morphology was examined with fluorescent confocal microscopy. Cells were stained for actin and nuclei, and there were noticeable differences between pristine nitinol samples compared to graphene-coated samples. Total actin expression from rat aortic smooth muscle cells was found using western blot. Protein adsorption characteristics, an indicator for potential thrombogenicity, were determined for serum albumin and fibrinogen with gel electrophoresis. Moreover, the transfer of charge from fibrinogen to substrate was deduced using Raman spectroscopy. It was found that graphene coating on nitinol substrates met the functional requirements for a stent material and improved the biological response compared to uncoated nitinol. Thus, graphene-coated nitinol is a viable candidate for a stent material.

Graphene offers potential as a coating material for biomedical implants. In this study we demonstrate a method for coating nitinol alloys with nanometer thick layers of graphene and determine how graphene may influence implant response.

Revestimentos de grafeno para implantes biomédicos

Atomically smooth graphene as a surface coating has potential to improve implant properties. This demonstrates a method for coating nitinol alloys with ...

Bioengenharia

Localization and Relative Quantification of Carbon Nanotubes in Cells with Multispectral Imaging Flow Cytometry

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich cell structures and de facto there is still no quantitative method to assess their distribution at cell and tissue levels. What we propose here is an innovative method allowing the detection and quantification of CNTs in cells using a multispectral imaging flow cytometer (ImageStream, Amnis). This newly developed device integrates both a high-throughput of cells and high resolution imaging, providing thus images for each cell directly in flow and therefore statistically relevant image analysis. Each cell image is acquired on bright-field (BF), dark-field (DF), and fluorescent channels, giving access respectively to the level and the distribution of light absorption, light scattered and fluorescence for each cell. The analysis consists then in a pixel-by-pixel comparison of each image, of the 7,000-10,000 cells acquired for each condition of the experiment. Localization and quantification of CNTs is made possible thanks to some particular intrinsic properties of CNTs: strong light absorbance and scattering; indeed CNTs appear as strongly absorbed dark spots on BF and bright spots on DF with a precise colocalization.
This methodology could have a considerable impact on studies about interactions between nanomaterials and cells given that this protocol is applicable for a large range of nanomaterials, insofar as they are capable of absorbing (and/or scattering) strongly enough the light.

In this study, the main purpose was to monitor the cellular uptake and eventual exocytosis of carbon nanotubes (CNTs). From this perspective, we proposed here a unique method using multispectral imaging flow cytometry allowing a quantification and localization of CNTs in a statistically relevant number of cells.

Carbon-based nanomaterials, like carbon nanotubes (CNTs), belong to this type of nanoparticles which are very difficult to discriminate from carbon-rich ...

Synthesis of an Intein-mediated Artificial Protein Hydrogel

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of this hydrogel are two protein block-copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. A highly hydrophilic random coil is inserted into one of the block-copolymers for water retention. Mixing of the two protein block copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit with crosslinkers at either end that rapidly self-assembles into a hydrogel. This hydrogel is very stable under both acidic and basic conditions, at temperatures up to 50 &#176;C, and in organic solvents. The hydrogel rapidly reforms after shear-induced rupture. Incorporation of a &#34;docking station peptide&#34; into the hydrogel building block enables convenient incorporation of &#34;docking protein&#34;-tagged target proteins. The hydrogel is compatible with tissue culture growth media, supports the diffusion of 20 kDa molecules, and enables the immobilization of bioactive globular proteins. The application of the intein-mediated protein hydrogel as an organic-solvent-compatible biocatalyst was demonstrated by encapsulating the horseradish peroxidase enzyme and corroborating its activity.

We present the synthesis of a split-intein-mediated protein hydrogel. The building blocks of this hydrogel are two protein copolymers each containing a subunit of a trimeric protein that serves as a crosslinker and one half of a split intein. Mixing of the two protein copolymers triggers an intein trans-splicing reaction, yielding a polypeptide unit that self-assembles into a hydrogel. This hydrogel is highly pH- and temperature-stable, compatible with organic solvents, and easily incorporates functional globular proteins.

Síntese de uma proteína artificial intein mediada Hidrogel

We present the synthesis of a highly stable protein hydrogel mediated by a split-intein-catalyzed protein trans-splicing reaction. The building blocks of ...

Synthesis of Keratin-based Nanofiber for Biomedical Engineering

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of these porous nanofibers is of great interest due to their unique physiochemical properties. Here we elaborate on the fabrication of keratin containing poly (&#949;-caprolactone) (PCL) nanofibers (i.e., PCL/keratin composite fiber). Water soluble keratin was first extracted from human hair and mixed with PCL in different ratios. The blended solution of PCL/keratin was transformed into nanofibrous membranes using a laboratory designed electrospinning set up. Fiber morphology and mechanical properties of the obtained nanofiber were observed and measured using scanning electron microscopy and tensile tester. Furthermore, degradability and chemical properties of the nanofiber were studied by FTIR. SEM images showed uniform surface morphology for PCL/keratin fibers of different compositions. These PCL/keratin fibers also showed excellent mechanical properties such as Young&#39;s modulus and failure point. Fibroblast cells were able to attach and proliferate thus proving good cell viability. Based on the characteristics discussed above, we can strongly argue that the blended nanofibers of natural and synthetic polymers can represent an excellent development of composite materials that can be used for different biomedical applications.

Electrospun nanofibers have a high surface area to weight ratio, excellent mechanical integrity, and support cell growth and proliferation. These nanofibers have a wide range of biomedical applications. Here we fabricate keratin/ PCL nanofibers, using the electrospinning technique, and characterize the fibers for possible applications in tissue engineering.

Síntese de nanofibras baseado em queratina de Engenharia Biomédica

Electrospinning, due to its versatility and potential for applications in various fields, is being frequently used to fabricate nanofibers. Production of ...

Engineering Molecular Recognition with Bio-mimetic Polymers on Single Walled Carbon Nanotubes

Semiconducting single-wall carbon nanotubes (SWNTs) are a class of optically active nanomaterial that fluoresce in the near infrared, coinciding with the optical window where biological samples are most transparent. Here, we outline techniques to adsorb amphiphilic polymers and polynucleic acids onto the surface of SWNTs to engineer their corona phases and create novel molecular sensors for small molecules and proteins. These functionalized SWNT sensors are both biocompatible and stable. Polymers are adsorbed onto the nanotube surface either by direct sonication of SWNTs and polymer or by suspending SWNTs using a surfactant followed by dialysis with polymer. The fluorescence emission, stability, and response of these sensors to target analytes are confirmed using absorbance and near-infrared fluorescence spectroscopy. Furthermore, we demonstrate surface immobilization of the sensors onto glass slides to enable single-molecule fluorescence microscopy to characterize polymer adsorption and analyte binding kinetics.

We present a protocol for engineering the corona phase of near infrared fluorescent single walled carbon nanotubes (SWNTs) using amphiphilic polymers and DNA to develop sensors for molecular targets without known recognition elements.

Reconhecimento Molecular de engenharia com Polymers Bio-mimético em únicos Walled nanotubos de carbono

Semiconducting single-wall carbon nanotubes (SWNTs) are a class of optically active nanomaterial that fluoresce in the near infrared, coinciding with the ...

Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. Recently, nanoparticles (NPs) have shown significant promise in the development of such delivery systems. Here, a liquid crystal NP (LCNP)-based delivery system has been employed for the controlled delivery of a water-insoluble dye, 3,3&#8242;-dioctadecyloxacarbocyanine perchlorate (DiO), from within the NP core to the hydrophobic region of a plasma membrane bilayer. During the synthesis of the NPs, the dye was efficiently incorporated into the hydrophobic LCNP core, as confirmed by multiple spectroscopic analyses. Conjugation of a PEGylated cholesterol derivative to the NP surface (DiO-LCNP-PEG-Chol) enabled the binding of the dye-loaded NPs to the plasma membrane in HEK 293T/17 cells. Time-resolved laser scanning confocal microscopy and F&#246;rster resonance energy transfer (FRET) imaging confirmed the passive efflux of DiO from the LCNP core and its insertion into the plasma membrane bilayer. Finally, the delivery of DiO as a LCNP-PEG-Chol attenuated the cytotoxicity of DiO; the NP form of DiO exhibited ~30-40% less toxicity compared to DiOfree delivered from bulk solution. This approach demonstrates the utility of the LCNP platform as an efficient modality for the membrane-specific delivery and modulation of hydrophobic molecular cargos.

A liquid crystal nanoparticle (LCNP) nanocarrier is exploited as a vehicle for the controlled delivery of a hydrophobic cargo to the plasma membrane of living cells.

Targeted Plasma Membrane entrega de um hidrofóbica Carga encapsulado em um cristal líquido nanopartículas Transportador

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. ...

DNA Nanotubes as a Versatile Tool to Study Semiflexible Polymers

Mechanical properties of complex, polymer-based soft matter, such as cells or biopolymer networks, can be understood in neither the classical frame of flexible polymers nor of rigid rods. Underlying filaments remain outstretched due to their non-vanishing backbone stiffness, which is quantified via the persistence length (lp), but they are also subject to strong thermal fluctuations. Their finite bending stiffness leads to unique, non-trivial collective mechanics of bulk networks, enabling the formation of stable scaffolds at low volume fractions while providing large mesh sizes. This underlying principle is prevalent in nature (e.g., in cells or tissues), minimizing the high molecular content and thereby facilitating diffusive or active transport. Due to their biological implications and potential technological applications in biocompatible hydrogels, semiflexible polymers have been subject to considerable study. However, comprehensible investigations remained challenging since they relied on natural polymers, such as actin filaments, which are not freely tunable. Despite these limitations and due to the lack of synthetic, mechanically tunable, and semiflexible polymers, actin filaments were established as the common model system. A major limitation is that the central quantity lp cannot be freely tuned to study its impact on macroscopic bulk structures. This limitation was resolved by employing structurally programmable DNA nanotubes, enabling controlled alteration of the filament stiffness. They are formed through tile-based designs, where a discrete set of partially complementary strands hybridize in a ring structure with a discrete circumference. These rings feature sticky ends, enabling the effective polymerization into filaments several microns in length, and display similar polymerization kinetics as natural biopolymers. Due to their programmable mechanics, these tubes are versatile, novel tools to study the impact of lp on the single-molecule as well as the bulk scale. In contrast to actin filaments, they remain stable over weeks, without notable degeneration, and their handling is comparably straightforward.

Semiflexible polymers display unique mechanical properties that are extensively applied by living systems. However, systematic studies on biopolymers are limited since properties such as polymer rigidity are inaccessible. This manuscript describes how this limitation is circumvented by programmable DNA nanotubes, enabling experimental studies on the impact of filament rigidity.

Nanotubos de DNA como uma ferramenta versátil para estudar semiflexível polímeros

Mechanical properties of complex, polymer-based soft matter, such as cells or biopolymer networks, can be understood in neither the classical frame of ...

Melt Electrospinning Writing of Three-dimensional Poly(&#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

Melt Electrospinning Writing of Three-dimensional Poly(&amp;#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This protocol serves as a comprehensive guideline to fabricate scaffolds via electrospinning with polymer melts in a direct writing mode. We systematically outline the process and define the appropriate parameter settings for achieving targeted scaffold architectures.

Derreter a eletrofiação escrita de andaimes Poly(ε-caprolactone) tridimensional com morfologias controláveis para aplicações de engenharia de tecidos

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology ...

Microhoneycomb Monoliths Prepared by the Unidirectional Freeze-drying of Cellulose Nanofiber Based Sols: Method and Extensions

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb monoliths (MHMs) with micrometer-scale channels are expected as efficient platforms for reactions and separations because of their large surface areas. Up to now, MHMs have been prepared by a unidirectional freeze-drying (UDF) method only from very limited precursors. Herein, we report a protocol from which a series of MHMs consisting of different components can be obtained. Recently, we found that cellulose nanofibers function as a distinct structure-directing agent towards the formation of MHMs through the UDF process. By mixing the cellulose nanofibers with water soluble substances which do not yield MHMs, a variety of composite MHMs can be prepared. This significantly enriches the chemical constitution of MHMs towards versatile applications.

Here, we present a general protocol to prepare a variety of microhoneycomb monoliths (MHMs) in which fluid can pass through with an extremely low pressure drop. MHMs obtained are expected to be used as filters, catalyst supports, flow-type electrodes, sensors and scaffolds for biomaterials.

Monólitos de Microhoneycomb preparados pela liofilização unidirecional de nanofibras de celulose com base Sols: método e extensões

Monolithic honeycomb structures have been attractive to multidisciplinary fields due to their high strength-to-weight ratio. Particularly, microhoneycomb ...

Synthesis of Multi-walled Carbon Nanotubes Modified with Silver Nanoparticles and Evaluation of Their Antibacterial Activities and Cytotoxic Properties

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver MWCNTs were prepared by the reductive deposition of silver from an aqueous solution of AgNO3 on the oxidized MWCNTs. Given the unique color of the CNTs, it was not possible to apply them to the minimum inhibitory concentration or mitochondrial toxicity assays to evaluate the toxicity and antibacterial properties, since they would interfere with the assays. The inhibition zone and minimum bactericidal concentration for the Ag-MWCNTs were measured and Live/Dead and Trypan Blue assays were used to measure the toxicity and antibacterial properties without interfering with the color of the CNTs.

In this study, antimicrobial nanomaterials were synthesized by acidic oxidation of multiwalled carbon nanotubes and subsequent reductive deposition of silver nanoparticles. Antimicrobial activity and cytotoxicity tests were performed with the as-prepared nanomaterials.

Síntese de nanotubos de carbono de paredes Multi modificados com nanopartículas de prata e avaliação das suas actividades antibacterianas e propriedades citotóxicas

In this study, multi-walled carbon nanotubes (MWCNTs) were treated with an aqueous sulfuric acid solution to form an oxygen-based functional group. Silver ...