Esta pesquisa foi apoiada pelo National Science Foundation da China (21474057 e 21604076).

atenção: favor consultar todas as fichas de dados de segurança (MSDS) antes do uso. Por favor, use as práticas de segurança adequadas ao realizar experimentos de química, incluindo o uso de uma coifa e equipamento de protecção pessoal (óculos de segurança, luvas de proteção, jaleco, etc.). O protocolo exige célula padrão manipulação técnicas (esterilização, recuperação da célula, célula passagem, congelamento de célula, coloracao celular, etc).
 1. preparação do hidrogel <ol><li>síntese do benzaldeído finalizado di-acrescida de polietileno glicol (PEG DF) <ol><li>pré-dessecação de PEG polímero <ol><li>pesar 4,00 g PEG (4.000 MW, 1.00 mmol), transferir para um balão de fundo redondo (250 mL) e adicionar tolueno (100 mL). 
			Nota: Outras PEGs com diferentes pesos moleculares pode trabalhar para a formação de hidrogel, mas levará a rigidez diferente.</li>
			<li>Aquecer a solução por uma pistola de calor (ou um prato quente em torno de 40 ° C) ligeiramente para ajudar a dissolver todos os polímeros. Depois de dissolvem todos os polímeros, use um evaporador para remover todos os solventes. Repita esse processo seco e dissolver duas vezes tornar o PEG secado polímeros. 
			Atenção: Esta deve ser executada em uma coifa com extremo cuidado. Tolueno é inflamável.</li>
		</ol></li> <li>Reação de terminação benzaldeído de PEG <ol><li>Adicionar um agitador magnético e tetrahidrofurano (THF, 100 mL) no balão e dissolver PEG, utilizando um agitador. Adicionar 4-carboxybenzaldehyde (0,90 g, 6,0 mmol) e 4-dimetilaminopiridina (0,07 g, 0,6 mmol) em sequência para as soluções para dissolver todos os sólidos completamente.</li>
			<li>Add N, N &#39;-dicyclohexylcarbodiimide (DCC, 1,25 g, 6,0 mmol) para a solução e adicionar um tubo de secagem que é preenchido com anidro CaCl 2 para o balão. Manter a reação sob agitação à temperatura ambiente (~ 20 ° C) por cerca de 12 h.</li>
		</ol></li> <li>Processo de pós-reação <ol><li>filtrar os sólidos brancos gerados na solução por vácuo, depois que a reação é terminada. Despeje a solução em éter dietílico frio (500 mL) sob agitação para precipitar os sólidos brancos. Reunir todos os sólidos brancos pelo filtro e seque os sólidos em uma coifa.</li>
			<li>Dissolver os sólidos brancos em THF novamente, filtrar qualquer sólidos insolúveis brancos, despeje a solução de éter dietílico frio fresco para precipitar os sólidos brancos e secá-lo. Repita este processo de duas a três vezes e em seguida, coloque os sólidos brancos em um forno de secagem a vácuo (20 ° C, 0.1 mbar) para secá-los completamente. Recolher o pó branco como o produto final: benzaldeído finalizado PEG DF.</li>
		</ol></li></ol></li> <li>Preparação do hidrogel <ol><li>pesar quantidades diferentes de PEG DF (0,11 g, 0,028 mmol g 0,22, 0.055 mmol; 0,44 g, 0.110 mmol) em um tubo (10 mL), adicionar água desionizada (5,0 mL) e use um vórtice ou agitador magnético para ajudar dissolver o polímero.</li>
		<li>Dissolver glicol quitosana (0,495 g, 6.18 x 10 -3 mmol) em água desionizada (15,0 mL) em um tubo (50 mL) e usar um vórtice por alguns minutos para homogeneizar a solução de quitosana (3% em peso).</li>
		<li>Adicionar a solução de quitosana glicol (0,2 mL, 3% em peso) e soluções DF PEG (0,2 mL) sequencialmente em um tubo (2,0 mL). Use um vórtice para misturar as soluções homogênea de hidrogel forma em vários minutos. Siga as proporções na tabela 1 tornar hidrogel de forças mecânicas diferentes. 
		Nota: Use o método do tubo-invertendo para determinar se o hidrogel já formou.</li>
	</ol></li> <li>Análises de reologia <ol><li>efectuar análises de reologia em um rheometer rotatória com uma placa de aço paralela (diâmetro: 20 mm). Para o teste de gelificação, espalhe o glicol solução de quitosana (0,2 mL, 3% em peso) em uma placa inferior. Em seguida, adicionar DF PEG soluções aquosas (0,2 mL, 2% em peso) gota uniformemente sobre a superfície da solução de quitosana e misture rapidamente com uma pipeta. Abaixe a placa superior e iniciar para teste</li>
		<li>De hidrogel &#39; s teste de rigidez, cortar um círculo um hidrogel (diâmetro: 20 mm) e medir o módulo de armazenamento (G &#39;) valores contra as análises de frequência na estirpe de 1%. G típico &#39; valores a 6,3 rad s &#8722; 1 estão listados na tabela 1. 
		Nota: Efectuar as análises de reologia do hidrogel 0,5 h após a formação de hidrogel para assegurar a estabilização de vínculo dinâmico do hidrogel.</li>
		<li>Para o hidrogel &#39; s auto reparáveis Propriedade testar, cortar um hidrogel em pedaços e juntar os pedaços de auto-recuperação de uma peça integrante. Em seguida, corte a peça de hidrogel para fazer um círculo (diâmetro: 20 mm) e colocá-lo sobre o rheometer para realizar a análise de reologia.</li>
	</ol></li></ol> 2. cultivo de célula 3D em hidrogel <ol><li>preparação de soluções de gelificação de hidrogel <ol><li>pesar DF PEG (0,44 g, 0.11 mmol) em um tubo estéril (4,0 mL), adicionar em meios de cultura celular (RPMI-1640, 2.0 mL) e usar um vórtice ou agitador para ajudar a dissolver o polímero para obter a solução de polímero (20% em peso). Carregar a solução em uma seringa (10,0 mL) e então ele esterilizar por passagem através de um filtro de bactérias-retentiva mícron (0,22 µm).</li>
		<li>Pesar a quitosana de glicol (0,165 g, 2,06 x 10 -3 mmol) em um tubo estéril (15,0 mL), adicionar em meios de cultura celular (RPMI-1640, 4,0 mL) e o vórtice para ajudar a dissolver o polímero para obter a solução de quitosana glicol (4,0% em peso). Carregar a solução em uma seringa (10,0 mL) e filtrá-la com um filtro de 0,22 µm bactérias-retentiva.</li>
	</ol></li> <li>Cultivo celular em hidrogel atenção: executar todos os procedimentos relacionados em uma capa de cultura de tecidos de células. Conhecimentos básicos de técnica estéril é esperado.
	<ol><li>Preparação da suspensão de células <ol><li>células L929 cultura RPMI-1640, suplementado com 10% FBS, 5% de penicilina (10 mL) em uma Petri prato (diâmetro 10 cm) e incubar a 37 ° C, 5% de CO 2. Mudar o meio todos os dias antes de usar.</li>
			<li>Colher as células L929 com PBS contendo tripsina (0,025% do w/v) e EDTA (0,01% w/v), centrifugar (70 x g, 5 min) e ressuspender as células em meio RPMI-1640 (1,0 mL). Realize a contagem de células usando a operação padrão da placa de contagem de sangue. Ressuspender as células para ajustar a concentração de células para ~ 3,75 × 10 6 células/mL.</li>
		</ol></li> <li>Encapsulamento de célula em hidrogel <ol><li>misturar as suspensões de células L929 (0,4 mL, 3,75 x 10 6 células mL -1) com solução de quitosana glicol (0,4 mL) em um tubo (4,0 mL) pelo vórtice. Pipetar a solução de quitosana L929/glicol (0,8 mL) para o centro de um prato de Petri confocal (diâmetro 2,0 cm). Pipetar as DF PEG soluções (0,2 mL) para o mesmo prato e pipetar delicadamente para misturar a solução e induzir a formação de hidrogel. 
			Nota: Avaliar a formação de hidrogel inclinando o prato de petri.</li>
			<li>Para cultura de células direta, adicionar quantidades adicionais de meios de cultura RPMI-1640 (1,0 mL) em cima do hidrogel. Colocar a célula incorporada hidrogel (1,0 mL, 1.5 wt % glicol quitosana, 4,0 wt % DF PEG, 1,5 × 10 6 células mL -1) em uma incubadora (37 ° C, 5% CO 2) e altere o meio todos os dias. Prepare-se para a imagem latente de célula no dia 1, 3, 5 e 7 após encapsulamento celular.</li>
		</ol></li> <li>Para a pós-cultura de células 3D em hidrogel após a injeção, preparar celular carregado hidrogel (1,0 mL, consulte a etapa 2.2.2) numa seringa (10,0 mL, agulha 48 G). Após as formas de hidrogel, injetar o hidrogel lentamente em uma placa de Petri para a imagem latente confocal. Adicionar um montante adicional de meios de cultura (1,0 mL) em cima do hidrogel e alterá-lo todos os dias. Coloque o prato de Petri em uma incubadora (37 ° C, 5% CO 2) e prepare-se para a imagem latente depois. 
		Atenção: Verifique e seguir o protocolo de operação de segurança de uma seringa.</li>
	</ol></li> <li>Análise de viabilidade de células <ol><li>Confocal observação <ol>
			<li>Enxaguar o hidrogel com PBS (1,0 mL) por duas vezes. Mancha o hidrogel com diacetato de fluoresceína (FDA, 0,5 mL, 0,05 mg/mL) e soluções de propidium iodeto (PI, 0,5 mL, 0,08 mg/mL) por 15 min. Depois da coloração, remover todos os solventes.</li>
			<li>Observar o hidrogel usando um microscópio confocal em comprimentos de onda de excitação de 488 nm e 543 nm a visualização ao vivo e mortos células, respectivamente. Leva pilhas através de cada profundidade de 2 µm do hidrogel para validar uma distribuição uniforme de células ao longo de z. 
			Nota: FDA manchas de células vivas enquanto PI manchas de células mortas.</li>
		</ol></li> <li>Degradar o hidrogel (1,0 mL) com ácido acético (HAc, 3% de v, 1,0 mL) por 5 min e pipetar para um tubo (4,0 mL). Coletar as células por centrifugação (70 x g, 5 min) e ressuspender as células em meio de cultura RPMI 1640 celular (1,0 mL). Executar célula contagem usando um sangue contagem placa.</li>
	</ol>
	</li>
</ol>

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Os autores não têm nada para divulgar.

O hidrogel apresentado neste protocolo (Figura 1) tem dois componentes principais: a polímero natural quitosana de glicol e um sintético benzaldeído encerrado gelator polímero PEG do DF, que são ambos os materiais biocompatíveis. Síntese do DF PEG é apresentado utilizando uma reação de modificação de uma etapa. PEG, de peso molecular 4.000 foi escolhida no presente protocolo em preocupações de solubilidade, eficiência de modificação, bem como rigidez de hidrogel. Uma série ...

Hidrogel é materiais de polímero reticulado com grandes quantidades de água e propriedades mecânicas macias, e eles têm sido usados em muitas aplicações bio-medical1,2. Hidrogel pode oferecer um ambiente suave e molhado, que é muito semelhante ao ambiente fisiológico para células em vivo. Portanto, hidrogel tornaram-se uma das plataformas mais populares para cultura de células 3D3,4. Em relação à cultura de pilha do prato de Petri 2D, cultura de células 3D avançou rapidamente para oferecer que uma matriz extracelular (ECM) imitou o microambiente para células de contato e montar para fins de proliferação e diferenciação5. Além disso, o hidrogel contendo polímeros naturais poderia oferecer biocompatível e promovendo ambientes para as células a proliferar e diferenciar3. Hidrogel derivado de polímeros sintéticos é preferidos para seus componentes simples e claras, que excluem influências complexas como as proteínas de origem animal ou vírus. Entre todos os candidatos de hidrogel para cultura de células 3D, hidrogel que facilmente é preparados e têm uma propriedade consistente é sempre preferidos. A facilidade para ajustar propriedades do hidrogel para atender necessidades diferentes pesquisas é importante como bem6.
Aqui apresentamos uma preparação superficial de um hidrogel de glicol baseado em quitosana usando química imina dinâmico, que se torna uma plataforma versátil de hidrogel para cultura de células 3D7. Neste método, conhecido biocompatível glicol quitosana são usados para estabelecer quadros de redes do hidrogel. Seus grupos aminoácidos são reagiu com um glicol de polietileno benzaldeído encerrado como o gelator de polímeros que formam ligações de imina dinâmico como crosslinkages de hidrogel8. Obrigações de imina dinâmico podem formar e decompor reversível e responsiva ao redor, dotando o hidrogel com quitosana mecanicamente ajustável redes9,10,11. Devido ao seu conteúdo de água de alto, materiais biocompatíveis e forças mecânicas ajustáveis, o hidrogel é aplicado com sucesso como um andaime para células L929 em cultura de células 3D12,13. O protocolo aqui detalha os procedimentos, incluindo a síntese de polímeros gelator, preparação de hidrogel, incorporação de célula e cultivo celular 3D.
O hidrogel também mostra várias outras características devido a sua crosslinkages de imina dinâmico, incluindo sua multi responsivo aos vários estímulos bio-(ácido e pH, piridoxal derivados de vitamina B6, papaína de proteína, etc), indicando que o hidrogel pode ser induzido a decompor-se sob condições fisiológicas8. O hidrogel é também auto reparáveis e injetável, o que significa que o hidrogel pode ser administrado através de um método de injeção invasiva mínima e ganhar uma vantagem em droga e célula entregas14,15. Pela adição de aditivos funcionais ou gelators de polímero preconcebidos específico, o hidrogel é compatível para obter propriedades específicas como magnética, temperatura, pH-responsivo, etc.16,,17, que pudesse cumprir um ampla gama de requisitos de pesquisa. Essas propriedades revelaram capacidade potencial do hydrogel ser um injetável várias transportadoras para drogas e células em ambos in vitro e em vivo pesquisa biomédica e aplicações.

<table border="0" cellpadding="0" cellspacing="0" width="1151">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:276px;">Glycol chitosan</td>
			<td style="width:360px;">Wako Pure Chemical Industries</td>
			<td style="width:131px;">39280-86-9</td>
			<td style="width:385px;">90% degree of deacetylation</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4-Carboxybenzaldehyde</td>
			<td>Shanghai Aladdin&#160;Bio-Chem Technology Co.,LTD</td>
			<td>619-66-9</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">N, N&#39;-dicyclohexylcarbodiimide</td>
			<td>Shanghai Aladdin&#160;Bio-Chem Technology Co.,LTD</td>
			<td>538-75-0</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Calcium chloride anhydrous</td>
			<td>Shanghai Aladdin&#160;Bio-Chem Technology Co.,LTD</td>
			<td>10043-52-4</td>
			<td>96%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4-dimethylamiopryidine</td>
			<td>Shanghai Aladdin&#160;Bio-Chem Technology Co.,LTD</td>
			<td>1122-58</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Polyethyleneglycol</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>5254-43-7</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Tetrahydrofuran</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>109-99-9</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Toluene</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>108-88-3</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Ethyl ether</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>60-29-7</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Acetic acid</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>64-19-7</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Anhydrous CaCl2</td>
			<td>Sino-pharm Chemical Reagent</td>
			<td>10043-52-4</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fluorescein diacetate</td>
			<td>Sigma</td>
			<td>596-09-8</td>
			<td>99%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Propidium iodide&#160;</td>
			<td>Sigma</td>
			<td>25535-16-4</td>
			<td>94%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">RPMI-1640 culture media</td>
			<td>Gibco</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Fetal bovine serum</td>
			<td>Gibco</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Trypsin-EDTA</td>
			<td>Gibco</td>
			<td></td>
			<td>0.25%</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">PBS</td>
			<td>Solarbio</td>
			<td></td>
			<td>0.01 M</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Penicillin streptomycin solution</td>
			<td>Hyclone</td>
			<td></td>
			<td>10,000 U/mL</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Rheometer</td>
			<td>TA Instrument</td>
			<td></td>
			<td>AR-G2</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Confocal microscope</td>
			<td>Zeiss</td>
			<td></td>
			<td>710-3channel</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">L929 Cells</td>
			<td>ATCC</td>
			<td></td>
			<td>NCTC clone 929; L cell, L929, derivative of Strain L</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Evaporator</td>
			<td>EYELA</td>
			<td></td>
			<td>N-1100</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">48 guage needle</td>
			<td>ShanghaiZhiyu Medical Material Co., LTD</td>
			<td></td>
			<td>48-guage</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microscope</td>
			<td>Leica</td>
			<td></td>
			<td>DM3000 B</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Microscope software</td>
			<td>Imaris</td>
			<td></td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Heat gun</td>
			<td>Confu</td>
			<td></td>
			<td>KF-5843&#160;</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Petri dish</td>
			<td>NEST</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

preparation of chitosan-based injectable hydrogels and its application in 3d cell culture

O protocolo apresenta um método fácil, eficiente e versátil para preparar hidrogel baseado em quitosana usando química imina dinâmico. O hidrogel é preparado misturando-se soluções de glicol quitosana com um gelator de polímero sintetizado benzaldeído finalizado e hidrogel com eficiência é obtidos em vários minutos à temperatura ambiente. Por razões diferentes entre quitosana glicol, gelator de polímero e conteúdo de água, obtêm-se versátil hidrogel com tempos diferentes de gelificação e rigidez. Quando danificadas, o hidrogel pode recuperar suas aparições e módulo de elasticidade, devido a reversibilidade das obrigações imina dinâmico como crosslinkages. Esta auto reparáveis propriedade permite que o hidrogel ser injetável, uma vez que pode ser auto curado de peças espremidas de um hidrogel em massa integral após o processo de injeção. O hidrogel é também multi sensível a muitos estímulos bio-ativos devido ao status de equilibração diferente das obrigações imina dinâmico. Este hidrogel foi confirmado como bio-compatível e células de fibroblasto de rato L929 foram incorporados procedimentos padrão e a proliferação das células foi facilmente avaliada por um processo de cultivo de células 3D. O hidrogel pode oferecer uma plataforma ajustável para diferentes pesquisas onde um mímico fisiológico de um ambiente 3D para as células é lucrou. Juntamente com suas propriedades multi responsivos, auto reparáveis e injetáveis, o hidrogel potencialmente pode ser aplicados como várias transportadoras para drogas e células em futuras aplicações biomédicas.

Uma apresentação esquemática do presente protocolo na preparação do hidrogel e seu uso como cultura de células 3D é oferecida na Figura 1. Informações do hidrogel conteúdo e rácios, preparados com diferentes forças mecânicas estão resumidas na tabela 1. O hidrogel é auto reparáveis e reologia Propriedade apresenta rigidez do hidrogel por módulo de armazenamento versus teste de frequência na Figura 2. As imagens confocal de cél...

Watch this Scientific Journal Video about Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture at JoVE.com

Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture

Aqui nós descrevemos uma preparação superficial de hidrogel injetável à base de quitosana usando química imina dinâmico. São apresentados métodos para ajustar a força mecânica do hidrogel e sua aplicação em cultura de células 3D.

Preparação do hidrogel injetável à base de quitosana e sua aplicação em cultura de células 3D

The protocol presents a facile, efficient, and versatile method to prepare chitosan-based hydrogels using dynamic imine chemistry. The hydrogel is ...

preparation-chitosan-based-injectable-hydrogels-its-application-3d

Research

JoVE Journal

Chemistry

18.9K visualizações.  Tsinghua University. Aqui nós descrevemos uma preparação superficial de hidrogel injetável à base de quitosana usando química imina dinâmico. São apresentados métodos para ajustar a força mecânica do hidrogel e sua aplicação em cultura de células 3D.

Vídeo: Preparation of Chitosan-based Injectable Hydrogels and Its Application in 3D Cell Culture

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

The development of fluorescent indicators represented a revolution for life sciences. Genetically encoded and synthetic fluorophores with sensing abilities allowed the visualization of biologically relevant species with high spatial and temporal resolution. Synthetic dyes are of particular interest thanks to their high tunability and the wide range of measureable analytes. However, these molecules suffer several limitations related to small molecule behavior (poor solubility, difficulties in targeting, often no ratiometric imaging allowed). In this work we introduce the development of dendrimer-based sensors and present a procedure for pH measurement in vitro, in living cells and in vivo. We choose dendrimers as ideal platform for our sensors for their many desirable properties (monodispersity, tunable properties, multivalency) that made them a widely used scaffold for several biomedical devices. The conjugation of fluorescent pH indicators to the dendrimer scaffold led to an enhancement of their sensing performances. In particular dendrimers exhibit reduced cell leakage, improved intracellular targeting and allow ratiometric measurements. These novel sensors were successfully employed to measure pH in living HeLa cells and in vivo in mouse brain.

Synthesis, Cellular Delivery and In vivo Application of Dendrimer-based pH Sensors

Fluorescence sensors are powerful tools in life science. Here we describe a methodology to synthesize and use dendrimer-based fluorescent sensors to measure pH in living cells and in vivo. The dendritic scaffold enhances the properties of conjugated fluorescent dyes leading to improved sensing properties.

Síntese, Entrega Celular e<em&gt; In vivo</em&gt; Aplicação de sensores de pH à base de Dendrímero

The development of  fluorescent indicators represented a revolution for life sciences. Genetically  encoded and synthetic fluorophores with sensing ...

Química

Isolation and Preparation of Bacterial Cell Walls for Compositional Analysis by Ultra Performance Liquid Chromatography

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the face of turgor pressures several atmospheres in magnitude. Across the diverse shapes and sizes of the bacterial kingdom, the cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by short peptides. Peptidoglycan&#8217;s central importance to bacterial physiology underlies its use as an antibiotic target and has motivated genetic, structural, and cell biological studies of how it is robustly assembled during growth and division. Nonetheless, extensive investigations are still required to fully characterize the key enzymatic activities in peptidoglycan synthesis and the chemical composition of bacterial cell walls. High Performance Liquid Chromatography (HPLC) is a powerful analytical method for quantifying differences in the chemical composition of the walls of bacteria grown under a variety of environmental and genetic conditions, but its throughput is often limited. Here, we present a straightforward procedure for the isolation and preparation of bacterial cell walls for biological analyses of peptidoglycan via HPLC and Ultra Performance Liquid Chromatography (UPLC), an extension of HPLC that utilizes pumps to deliver ultra-high pressures of up to 15,000 psi, compared with 6,000 psi for HPLC. In combination with the preparation of bacterial cell walls presented here, the low-volume sample injectors, detectors with high sampling rates, smaller sample volumes, and shorter run times of UPLC will enable high resolution and throughput for novel discoveries of peptidoglycan composition and fundamental bacterial cell biology in most biological laboratories with access to an ultracentrifuge and UPLC.

The bacterial cell wall is composed of peptidoglycan, a macromolecular network of sugar strands crosslinked by peptides. Ultra Performance Liquid Chromatography provides high resolution and throughput for novel discoveries of peptidoglycan composition. We present a procedure for the isolation of cell walls (sacculi) and their subsequent preparation for analysis via UPLC.

Isolamento e Preparação de Paredes Celulares Bacterianas para Análise Composicional por Cromatografia Líquida de Ultra Desempenho

The bacterial cell wall is critical for the determination of cell shape during growth and division, and maintains the mechanical integrity of cells in the ...

Preparation and Use of Carbonyl-decorated Carbenes in the Activation of White Phosphorus

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures in multi-gram scale quantities. The goal of this manuscript is to clearly detail how to handle and prepare these unique carbenes such that a synthetic chemist of any skill level can work with them. The two carbenes described are a diamidocarbene (DAC, carbene 1) and a monoamidoaminocarbene (MAAC 2). These carbenes are highly electron-deficient and as such display reactivity profiles that are atypical of more traditional N-heterocyclic carbenes. Additionally, these two carbenes only differ in their electrophilic character and not their steric parameters, making them ideal for studying how carbene electronics influence reactivity. To demonstrate this phenomenon, we are also describing the activation of white phosphorus (P4) using these carbenes. Depending on the carbene used, two very different phosphorus-containing compounds can be isolated. When the DAC 1 is used, a tris(phosphaalkenyl)phosphane can be isolated as the exclusive product. Remarkably however, when MAAC 2 is added to P4 under identical reaction conditions, an unexpected carbene-supported P8&#160;allotrope of phosphorus is isolated exclusively. Mechanistic studies demonstrate that this carbene-supported P8allotrope forms via a [2+2] cycloaddition dimerization of a transient diphosphene which has been trapped by treatment with 2,3-dimethyl-1,3-butadiene.

Here, we present a protocol for the synthesis of two carbonyl-decorated carbenes. The protocol makes these interesting compounds readily available to chemists of all skill levels. In addition to the synthesis of these two carbenes, their use in the activation of white phosphorus is also described.

Preparação e Utilização de carbenos Carbonyl decorados na ativação de fósforo branco

Here we present a protocol for the synthesis of two distinct carbonyl-decorated carbenes. Both carbenes can be prepared using nearly identical procedures ...

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical (Methylation) and Physical (Mass Spectrometry, Nuclear Magnetic Resonance) Techniques

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans. De-starched wheat endosperm cell walls were isolated as an alcohol-insoluble residue (AIR)1 and sequentially extracted with water (W-sol Fr) and 1 M KOH containing 1% NaBH4 (KOH-sol Fr) as described by Ratnayake et al. (2014)2. Two different approaches (see summary in Figure 1) are adopted. In the first, intact W-sol AXs are treated with 2AB to tag the original RE backbone chain sugar residue and then treated with an endoxylanase to generate a mixture of 2AB-labelled RE and internal region reducing oligosaccharides, respectively. In a second approach, the KOH-sol Fr is hydrolyzed with endoxylanase to first generate a mixture of oligosaccharides which are subsequently labelled with 2AB. The enzymically released ((un)tagged) oligosaccharides from both W- and KOH-sol Frs are then methylated and the detailed structural analysis of both the native and methylated oligosaccharides is performed using a combination of MALDI-TOF-MS, RP-HPLC-ESI-QTOF-MS and ESI-MSn. Endoxylanase digested KOH-sol AXs are also characterized by nuclear magnetic resonance (NMR) that also provides information on the anomeric configuration. These techniques can be applied to other classes of polysaccharides using the appropriate endo-hydrolases.

Sequencing of Plant Wall Heteroxylans Using Enzymic, Chemical Methylation and Physical Mass Spectrometry, Nuclear Magnetic Resonance Techniques

This protocol describes the specific techniques used for the structural characterization of reducing end (RE) and internal region glycosyl sequence(s) of heteroxylans by tagging the RE with 2 aminobenzamide prior to enzymatic (endoxylanase) hydrolysis and then analysis of the resultant oligosaccharides using mass spectrometry (MS) and nuclear magnetic resonance (NMR).

Sequenciamento de parede planta heteroxilanos Usando enzimática, química (metilação) e físico (espectrometria de massa, ressonância magnética nuclear) Técnicas

This protocol describes the specific techniques used for the characterization of reducing end (RE) and internal region glycosyl sequence(s) of ...

Investigations on the Ga(III) Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue

We demonstrate a method for the isolation of EOB-DTPA (3,6,9-triaza-3,6,9-tris(carboxymethyl)-4-(ethoxybenzyl)-undecanedioic acid) from its Gd(III) complex and protocols for the preparation of its novel non-radioactive, i.e., natural Ga(III) as well as radioactive 68Ga complex. The ligand as well as the Ga(III) complex were characterized by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry and elemental analysis. 68Ga was obtained by a standard elution method from a 68Ge/68Ga generator. Experiments to evaluate the 68Ga-labeling efficiency of EOB-DTPA at pH 3.8&#8211;4.0 were performed. Established analysis techniques radio TLC (thin layer chromatography) and radio HPLC (high performance liquid chromatography) were used to determine the radiochemical purity of the tracer. As a first investigation of the 68Ga tracers&#39; lipophilicity the n-octanol/water distribution coefficient of 68Ga species present in a pH 7.4 solution was determined by an extraction method. In vitro stability measurements of the tracer in various media at physiological pH were performed, revealing different rates of decomposition.

Investigations on the GaIII Complex of EOB-DTPA and Its 68Ga Radiolabeled Analogue

A procedure for the isolation of EOB-DTPA and subsequent complexation with natural Ga(III) and 68Ga is presented herein, as well as a thorough analysis of all compounds and investigations on labeling efficiency, in vitro stability and the n-octanol/water distribution coefficient of the radiolabeled complex.

As investigações sobre o Complexo Ga (III) de EOB-DTPA e sua<sup&gt; 68</sup&gt; Ga Radiolabeled Analogue

We demonstrate a method for the isolation of EOB-DTPA (3,6,9-triaza-3,6,9-tris(carboxymethyl)-4-(ethoxybenzyl)-undecanedioic acid) from its Gd(III) ...

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We present methods for depositing and passively manipulating C60 molecules on rippled graphene that advance the pursuit of realizing applications involving 1D C60/graphene hybrid structures. The techniques applied in this exposition are geared towards high vacuum systems with preparation areas capable of supporting molecular deposition as well as thermal annealing of the samples. We focus on C60 deposition at low pressure using a homemade Knudsen cell connected to a scanning tunneling microscopy (STM) system. The number of molecules deposited is regulated by controlling the temperature of the Knudsen cell and the deposition time. One-dimensional (1D) C60 chain structures with widths of two to three molecules can be prepared via tuning of the experimental conditions. The surface mobility of the C60 molecules increases with annealing temperature allowing them to move within the periodic potential of the rippled graphene. Using this mechanism, it is possible to control the transition of 1D C60 chain structures to a hexagonal close packed quasi-1D stripe structure.

Preparation and Characterization of C60/Graphene Hybrid Nanostructures

Here we present a protocol for the fabrication of C60/graphene hybrid nanostructures by physical thermal evaporation. Particularly, the proper manipulation of deposition and annealing conditions allow the control over the creation of 1D and quasi 1D C60 structures on rippled graphene.

Preparação e caracterização de nanoestruturas de híbrido C60/Graphene

Physical thermal deposition in a high vacuum environment is a clean and controllable method for fabricating novel molecular nanostructures on graphene. We ...

Bio-inspired Polydopamine Surface Modification of Nanodiamonds and Its Reduction of Silver Nanoparticles

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a simple protocol for the multifunctional surface modification of NDs by using mussel-inspired polydopamine (PDA) coating. In addition, the functional layer of PDA on NDs could serve as a reducing agent to synthesize and stabilize metal nanoparticles. Dopamine (DA) can self-polymerize and spontaneously form PDA layers on ND surfaces if the NDs and dopamine are simply mixed together. The thickness of a PDA layer is controlled by varying the concentration of DA. A typical result shows that a thickness of ~5 to ~15 nm of the PDA layer can be reached by adding 50 to 100 &#181;g/mL of DA to 100 nm ND suspensions. Furthermore, the PDA-NDs are used as a substrate to reduce metal ions, such as Ag[(NH3)2]+, to silver nanoparticles (AgNPs). The sizes of the AgNPs rely on the initial concentrations of Ag[(NH3)2]+. Along with an increase in the concentration of Ag[(NH3)2]+, the number of NPs increases, as well as the diameters of the NPs. In summary, this study not only presents a facile method for modifying the surfaces of NDs with PDA, but also demonstrates the enhanced functionality of NDs by anchoring various species of interest (such as AgNPs) for advanced applications.

A facile protocol is presented to functionalize the surfaces of nanodiamonds with polydopamine.

Modificação de superfície de Polydopamine bio-inspirada de nanodiamantes e sua redução de nanopartículas de prata

Surface functionalization of nanodiamonds (NDs) is still challenging due to the diversity of functional groups on the ND surfaces. Here, we demonstrate a ...

Photogeneration of N-Heterocyclic Carbenes: Application in Photoinduced Ring-Opening Metathesis Polymerization

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes and determine the corresponding photochemical mechanism. Then, we describe a protocol to perform ring-opening metathesis polymerization (ROMP) in solution and in miniemulsion using this NHC-photogenerating system. To photogenerate IMes, a system comprising 2-isopropylthioxanthone (ITX) as the sensitizer and 1,3-dimesitylimidazolium tetraphenylborate (IMesH+BPh4-) as the protected form of NHC is employed. IMesH+BPh4- can be obtained in a single step by anion exchange between 1,3-dimesitylimidazolium chloride and sodium tetraphenylborate. A real-time steady-state photolysis setup is described, which hints that the photochemical reaction proceeds in two consecutive steps: 1) ITX triplet is photo-reduced by the borate anion and 2) subsequent proton transfer takes place from the imidazolium cation to produce the expected NHC IMes. Two separate characterization protocols are implemented. Firstly, CS2 is added to the reaction media to evidence the photogeneration of NHC through formation of the IMes-CS2 adduct. Secondly, the amount of NHC released in situ is quantified using acid-base titration. The use of this NHC photo-generating system for the ROMP of norbornene is also discussed. In solution, a photopolymerization experiment is conducted by mixing ITX, IMesH+BPh4-, [RuCl2(p-cymene)]2 and norbornene in CH2Cl2, then irradiating the solution in a UV reactor. In a dispersed medium, a monomer miniemulsion is first formed then irradiated inside an annular reactor to produce a stable poly(norbornene) latex.

We describe a protocol to photogenerate N-heterocyclic carbenes (NHCs) by UV irradiation of a 2-isopropylthioxanthone/imidazolium tetraphenylborate salt system. Methods to characterize the photoreleased NHC and elucidate the photochemical mechanism are proposed. The protocols for ring-opening metathesis photopolymerization in solution and miniemulsion illustrate the potential of this 2-component NHC photogenerating system.

Pseudo-levitante de N-Heterocyclic carbenos: aplicação na polimerização de metátese de anel-abertura de participação

We report a method to generate the N-heterocyclic carbene (NHC) 1,3-dimesitylimidazol-2-ylidene (IMes) under UV-irradiation at 365 nm to characterize IMes ...

Preparation and Application of a New Bacterial Biosensor for the Presumptive Detection of Gunshot Residue

MicRoboCop is a biosensor that has been designed for a unique application in forensic chemistry. MicRoboCop is a system made up of three devices that, when used together, can indicate the presence of gunshot residue (GSR) by producing a fluorescence signal in the presence of three key analytes (antimony, lead, and organic components of GSR). The protocol describes the synthesis of the biosensors using Escherichia coli (E. coli), and the analytical chemistry methods used to evaluate the selectivity and sensitivity of the sensors. The functioning of the system is demonstrated by using GSR collected from the inside of a spent cartridge casing. Once prepared, the biosensors can be stored until needed and can be used as a test for these key analytes. A positive response from all three analytes provides a presumptive positive test for GSR, while each individual device has applications for detecting the analytes in other samples (e.g., a detector for lead contamination in drinking water). The main limitation of the system is the time required for a positive signal; future work may involve studying different organisms to optimize the response time.

A protocol is presented using synthetic biology techniques to synthesize a set of bacterial biosensors for the analysis of gunshot residue, and to test the functioning of the devices for their intended use using fluorescence spectroscopy.

Preparação e aplicação de um novo biosensor bacteriano para a detecção presuntiva de resíduo de bala

MicRoboCop is a biosensor that has been designed for a unique application in forensic chemistry. MicRoboCop is a system made up of three devices that, ...

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. The versatility of the GSMLCs is demonstrated in the context of a study about etching and growth dynamics of gold nanostructures from a HAuCl4 precursor solution. GSMLCs combine the advantages of conventional silicon- and graphene-based liquid cells by offering reproducible well depths together with facile cell manufacturing and handling of the specimen under investigation. The GSMLCs are fabricated on a single silicon substrate which drastically reduces the complexity of the manufacturing process compared to two-wafer-based liquid cell designs. Here, no bonding or alignment process steps are required. Furthermore, the enclosed liquid volume can be tailored to the respective experimental requirements by simply adjusting the thickness of a silicon nitride layer. This enables a significant reduction of window bulging in the electron microscope vacuum. Finally, a state-of-the-art quantitative evaluation of single particle tracking and dendrite formation in liquid cell experiments using only open source software is presented.

Preparation of Graphene-Supported Microwell Liquid Cells for In Situ Transmission Electron Microscopy

A protocol for preparation of graphene-supported microwell liquid cells for in situ electron microscopy of gold nanocrystals from HAuCl4 precursor solution is presented. Furthermore, an analysis routine is presented to quantify observed etching and growth dynamics.

Preparação de células líquidas de micropoços suportadas por grafeno para microscopia eletrônica de transmissão in situ

The fabrication and preparation of graphene-supported microwell liquid cells (GSMLCs) for in situ electron microscopy is presented in a stepwise protocol. ...

Preparação do hidrogel injetável à base de quitosana e sua aplicação em cultura de células 3D

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