Este trabalho foi financiado pelo NIH subvenções: HL671795, HL048743 e HL108630.

1. Preparação de SDF-1α Glicano Nanopartículas Devido ao efeito da administração in vivo, esterilizar todos os recipientes, pipetas, e pontas usadas na preparação. <ol><li> Prepare as seguintes soluções de em água ultrapura: 1% de sulfato de dextrano; NaOH 1 M (esterilizado por filtração com uma membrana PES); Quitosano a 0,1% em 0,2% de ácido acético glacial (0,8 e filtra-se através de filtros de 0,22 um, consecutivamente e ajustar o pH para 5,5 com NaOH depois); 0,1 M ZnSO4; 15% de manitol; e 0,92 mg / ml de SDF-1α (armazenado em alíquotas a 80 ° C, e mantida a 4 ° C uma vez descongelado). </li><li> Esteriliza-se através de soluções de estoque 0,22 mM membranas de filtro. Avaliar os níveis de endotoxina na solução preparada com ensaio limulus amebócito lisado (LAL) coágulo de gel. Certifique-se que os níveis são &lt;0,06 EU / ml. </li><li> Adicionar 0,18 ml de água ultrapura para um frasco de vidro de 1,5 ml contendo uma barra de agitação magnética. Defina a velocidade de agitação a 800 rpm. Adicionar 0,1 ml de 1%sulfato de dextrano e agita-se durante 2 min. Adicionar 0,08 mg SDF-1α (0,087 ml de 0,92 mg / ml de SDF-1α solução) e agitar durante 20 min. </li><li> Adicionar 0,33 ml de 0,1% de quitosano, gota a gota e agita-se durante 5 min. Alterar a velocidade de agitação para o máximo e adicionar 0,1 ml de 0,1 M ZnSO4 lentamente com uma seringa de 0,1 mL (ao longo de 1 min). </li><li> Retorno velocidade de agitação para 800 rpm e mexa por 30 min. Adicionar 0,4 ml de 15% de manitol e agita-se durante 5 min. Transferir a mistura reaccional para um tubo de microcentrífuga de 1,5 ml. Centrifugar a 16.000 xg, a 4 ° C durante 10 min. Nota: A presença de manitol facilita a ressuspensão das partículas após centrifugação. Dependendo da compactação do sedimento, a concentração de manitol pode variar de 0% a 5%. Ressuspensão completa das partículas após cada centrifugação é crítico para evitar agregados na suspensão final. </li><li> Aspirar o sobrenadante e utilizar uma pipeta para remover a última gota do líquido lentamente. Adicionar 0,2 ml de 5% de manitol. Suspender o pellet com 0,5 ml, 29 G needle seringa. Adicionar 1 ml de 5% de manitol. Centrifuga-se a 16000 xg durante 15 min. </li><li> Repita o passo 1.6. </li><li> Aspirar o sobrenadante. Ressuspender o sedimento em 0,2 ml de 5% de manitol. Armazenar a suspensão de partículas a 4 ° C. Nota: A suspensão de partículas também pode ser armazenado congelado a -80 ° C ou liofilizado. Incluindo 5% de manitol em suspensão é essencial para evitar a agregação das partículas após congelação e descongelação ou após liofilização e re-hidratação. O manitol pode ser removido por centrifugação da suspensão, após o armazenamento. </li></ol> 2. A medição do tamanho de partícula e Potencial Zeta O tamanho de partícula e potencial zeta são analisados ​​por dispersão de luz dinâmica e electroforético da dispersão de luz, respectivamente, com um analisador de partículas indicada na lista de materiais. <ol><li> Configure os seguintes parâmetros para medição do tamanho de partícula: tempos de Capitalização: 70; Repita vezes: 4; Temperatura: 25 ° C;Diluente: água; Ajuste de intensidade: auto. </li><li> Dilui-se a amostra SDF-1α-DS-CS com água (diluição de 10 vezes). Carregar 100 ul da amostra a uma cuvete descartável de UV, tais como numa cuvete de Eppendorf. Coloque a célula no suporte da célula. Aguarde até que o ajuste de intensidade para chegar a &quot;Optimum&quot; (~ 10.000 cps). Iniciar a aquisição de dados. </li><li> Após a medição está completa, gravar os resultados cumulantes de diâmetro (nm) e índice de polidispersão. Calcular a média dos resultados obtidos a partir de cada uma das quatro leituras repetidas e calcular o desvio padrão. </li><li> Carga de 500 ul de 10 vezes a amostra diluída partícula a uma célula de fluxo para medição do potencial zeta. Configure os seguintes parâmetros para a medição: tempos de Capitalização: 10; Repita vezes: 5; Temperatura: 25 ° C; Diluente: água; Ajuste de intensidade: auto. Registam-se os resultados do potencial zeta (mV). Média, o resultado de cada um dos 5 leituras repetidas, e calcular o deviatio padrãon. </li></ol> 3. Quantificação de SDF-1α nas Partículas <ol><li> Dilui-se em forma livre SDF-1α a concentrações de 0,01, 0,02, 0,03, 0,04, e 0,05 mg / ml em tampão de amostra de Laemmli 1,3x. Diluir 6 ul amostras SDF-1α-DS-CS com tampão de amostra de 40 ul 1,3x Laemmli. (Preparar tampão de Laemmli 4x estoque contendo 0,25 M de Tris-HCl, pH 7,5, 8% SDS, 40% glicerol, 0,05 mg / ml de azul de bromofenol, e 8% de 2-mercaptoetanol. Dividir a solução estoque em pequenas alíquotas a -20 e manter ° C para uso individual.) </li><li> Aquecer as amostras a 100 ° C durante 10 min. Agitar as amostras duas vezes (cada uma de 10 segundos à velocidade máxima) durante o tempo de aquecimento de 10 min de modo a dissociar as partículas completamente. Arrefecer as amostras até à TA durante 2 min. Centrífuga a 10.000 xg por 0,5-1 min para derrubar o condensado de água. Vortex novamente para misturar bem. Nota: Neste ponto, a solução da amostra deve ser límpida sem precipitados visíveis presentes. </li><li> Carga 10 &amp;# 181; l sample / bem a um gel SDS 4-20%. Executar electroforese a 200 V durante 20 min. Manchar o gel com Coomassie mancha azul proteína. </li><li> Examinar a densidade de banda de proteína de SDF-1α usando um gerador de imagens e análise de densitometria software molecular. Calcular a quantidade de SDF-1α nas partículas contra uma curva padrão construída com padrões SDF-1α livres. </li></ol> 4. Ensaio de Libertação In Vitro <ol><li> Misturar partículas de glicano SDF-1α com solução salina tamponada com fosfato de Dulbecco sem cálcio e magnésio (D-PBS) a uma proporção de 1: 1 (v / v). </li><li> Dividir a suspensão de partículas em 0,05 ml de partes alíquotas em tubos de 1,5 ml. Coloque as amostras para o fundo dos tubos. Evitar a introdução de bolhas de ar ou perturbar a superfície do líquido. Selar o topo dos tubos com parafilme. NOTA: Ao fazer isso, o líquido irá permanecer na parte inferior durante a rotação de cima para baixo subsequente sobre o misturador tubo. </li><li> Gire os tubos a 37 &amp;# 176; C em um giro Micro-Tube Mixer. Retirar as alíquotas de nos tempos designados, e imediatamente centrifugar as amostras a 16.000 xg durante 10 min a 4 ° C. </li><li> Separa-se os sobrenadantes e peletes, e reconstituir o sedimento com 0,05 ml de D-PBS. Armazenar as amostras a -20 ° C. Depois de todas as amostras são recolhidas, examinar-se os sobrenadantes e peletes sobre um gel de SDS como descrito acima. </li></ol> 5. Migration Assay Este ensaio mede a actividade quimiotáctica de SDF-1α. Interacção de SDF-1α com o seu receptor (CXCR4) na superfície da célula causa a migração da célula no sentido do gradiente de SDF-1α. Neste ensaio, as células são carregadas para um bem superior (separados por uma membrana semi-permeável, a partir de um poço inferior) e SDF-1α solução em um tubo inferior. <ol><li> Diluir SDF-1α (forma livre ou ligado a partículas) com tampão de migração (meio RPMI-1640 contendo 0,5% de albumina de soro de bovino) na proporção de 3-FOld diluição em série para as concentrações finais de 100, 33, 11, 3,7, 1,2, 0,41, 0,14, e 0,05 ng / ml. </li><li> Adicionar 0,6 ml de solução a SDF-1α diluída ou tampão de migração apenas (controlo negativo) a uma cavidade da placa de 24 poços. Adicionar tampão migração 0,57 ml a um bem (controle de célula de entrada). Incubar a 37 ° C durante 30 min. Coloque uma inserção de cultura de célula Transwell permeável tal como (tamanho de poro de 5 um, 6,5 mm de diâmetro) na parte superior do poço inferior. Carregar 0,1 ml de células de Jurkat (5 x 10 5) para inserir o Transwell. Coloque 0,03 ml de células directamente para a célula de entrada de controlo bem. Incubar a placa a 37 ° C durante 2 horas numa atmosfera de 5% de CO2. </li><li> Remova as inserções Transwell. Transferem-se as células que migraram para os poços inferiores a um tubo de poliestireno de 4 ml. Contar as células migraram com um citômetro de fluxo. </li><li> Calcular a migração como uma percentagem do número de células de entrada (o número de células no controlo de célula de entrada bem x 100/30) após subtracção dos números em negative controles (células migraram para os poços contendo tampão migração só). </li></ol>

<ol>
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The authors declare that they have no competing financial interests.

Como mencionado acima, as nanopartículas DS-CS são formados através de neutralização de cargas entre polianião (DS) e policatião (CS) moléculas. Uma vez que a interacção de cargas ocorre prontamente durante a colisão molecular, a concentração das soluções de polímero e a velocidade de agitação durante a mistura é crítica para o tamanho das partículas resultantes. A tendência geral é que DS e CS 15 soluções e maior resultado velocidade de agitação em partículas menores mais diluído...

O sulfato de dextrano (DS) e quitosana (CS) são polissacarídeos com múltiplas substituídos grupos sulfato carregados negativamente (em DS), ou grupos amina carregados positivamente (desacetilados CS). Quando misturado numa solução aquosa, os dois polissacáridos formar complexos de polielectrólitos através de interacções electrostáticas. Os complexos resultantes podem formar grandes agregados que irá ser progressivamente-separado da solução aquosa (ou precipitados), pequenas partículas que são dispersíveis em água (colóides). As condições específicas que contribuem para esses resultados têm sido extensivamente estudada, e foram resumidos e ilustrado em pormenor numa publicação recente 1. Entre essas condições, dois requisitos básicos para a produção de partículas dispersíveis em água são os polímeros de carga oposta deve 1) têm massa molar significativamente diferente; e 2) ser misturado numa relação não estequiométrica. Estas condições permitirão que os segmentos poliméricos complexados carga neutra gerados pela carganeutralização para segregar e formar o núcleo da partícula, e o excesso de polímero para formar o invólucro exterior 1. As partículas de glicanos descritos neste protocolo são destinados para a administração pulmonar, e são projetados para serem net carregado negativamente, e de dimensões nanométricas. A carga de superfície negativa reduz a probabilidade de absorção celular das partículas de 2,3. Partículas de dimensão nanométrica facilitar a passagem através das vias aéreas distais. Para atingir este objectivo, a quantidade de DS utilizado nesta preparação é em excesso de CS (proporção em peso de 3: 1); e alta massa molecular DS (peso-médio MW 500.000) e de baixo peso molecular, CS (MW gama 50-190 kDa, 75-85% desacetilada) são usadas. SDF-1α é um factor homing células estaminais, que exerce a função de homing através da sua actividade quimiotáctica. SDF-1α desempenha um papel importante no retorno e manutenção de células estaminais hematopoiéticas na medula óssea e no recrutamento de ProgeNitor células no tecido periférico para a reparação de lesão 4,5. SDF-1α tem um local de ligação à heparina na sequência da proteína, o que permite que a proteína se liga à heparina / sulfato de heparano, formam dímeros, ser protegido contra a protease (CD26 / DPPIV) inactivação, e interagem com células alvo através dos receptores de superfície celular 6-8. DS tem propriedades estruturais semelhantes às da heparina / sulfato de heparano; assim, a ligação de SDF-1α para DS seria semelhante à dos seus ligantes poliméricos naturais. No protocolo seguinte, descreve-se a preparação de nanopartículas de SDF-1α-DS-CS. Os procedimentos representam uma das formulações que foram previamente estudadas 9. O protocolo é originalmente adaptado de uma investigação do VEGF-DS-CS nanopartículas 10. Uma preparação em pequena escala é descrito, o qual pode ser facilmente dimensionado para cima com as mesmas soluções de reserva e as condições de preparação. Após a preparação, as partículas são caracterizadas by examinar seu tamanho, potencial zeta, a extensão da incorporação SDF-1α, in vitro tempo de liberação e atividade do incorporada SDF-1α.

<table border="0" cellpadding="0" cellspacing="0" width="489">
	<tbody>
		<tr height="20">
			<td height="20" style="height:20px;width:255px;">Name</td>
			<td style="width:136px;">Company</td>
			<td style="width:99px;">Catalog number</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Dextran sulfate</td>
			<td>Fisher</td>
			<td>BP1585-100</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Chitosan, low molecular weight&#160;</td>
			<td>Sigma</td>
			<td>448869</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Zinc sulfate heptahydrate</td>
			<td>Sigma</td>
			<td>204986</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">D-Mannitol</td>
			<td>Sigma</td>
			<td>M9546</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">UltraPure water&#160;</td>
			<td>Invitrogen&#160;</td>
			<td>10977-023</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">SDF-1&#945;</td>
			<td>Prepared according to reference 8.</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Syringe filter, PES membrane 0.22 um.&#160;&#160;&#160;</td>
			<td>Millipore</td>
			<td>SLGP033RS</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Magnetic Micro Stirring Bars (2 x 7 mm)</td>
			<td>Fisher&#160;</td>
			<td>14-513-63</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Glass vial Kit; SUN-SRi</td>
			<td>Fisher&#160;</td>
			<td>14-823-182</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Delsa Nano C Particle Analyzer&#160;</td>
			<td>Backman Coulter</td>
			<td></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Eppendorf UVette Cuvets</td>
			<td>Eppendorf</td>
			<td>952010069</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">4&#8211;20% Mini-PROTEAN TGX Gel</td>
			<td>Bio-Rad</td>
			<td>456-1096</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">GelCode Blue Safe Protein Stain</td>
			<td>Fisher&#160;</td>
			<td>PI-24592</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Molecular Imager VersaDoc MP 4000 System</td>
			<td>BioRad</td>
			<td>170-8640</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Corning Transwell Permeable Supports</td>
			<td>Corning</td>
			<td>3421</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Accuri C6 Flow Cytometer</td>
			<td>BD Biosciences</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s phosphate buffered saline&#160;</td>
			<td>Sigma</td>
			<td>D8537</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">Pyrogent plus kit</td>
			<td>Fisher</td>
			<td>NC9753738</td>
		</tr>
	</tbody>
</table>

preparation and characterization of sdf-1&#945;-chitosan-dextran sulfate nanoparticles

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under appropriate conditions. The glycan nanoparticles are useful carriers for protein factors, which facilitate the in vivo delivery of the proteins and sustain their retention in the targeted tissue. The glycan polyelectrolyte complexes are also ideal for protein delivery, as the incorporation is carried out in aqueous solution, which reduces the likelihood of inactivation of the proteins. Proteins with a heparin-binding site adhere to dextran sulfate readily, and are, in turn, stabilized by the binding. These particles are also less inflammatory and toxic when delivered in vivo. In the protocol described below, SDF-1&#945; (Stromal cell-derived factor-1&#945;), a stem cell homing factor, is first mixed and incubated with dextran sulfate. Chitosan is added to the mixture to form polyelectrolyte complexes, followed by zinc sulfate to stabilize the complexes with zinc bridges. The resultant SDF-1&#945;-DS-CS particles are measured for size (diameter) and surface charge (zeta potential). The amount of the incorporated SDF-1&#945; is determined, followed by measurements of its in vitro release rate and its chemotactic activity in a particle-bound form.

O tamanho e potencial zeta das partículas preparadas SDF-1α-DS-CS são determinadas com um analisador de partículas. A Figura 1 mostra a análise da medição do tamanho. A partir dos resultados obtidos a partir de quatro cumulantes medições repetidas, o diâmetro hidrodinâmico médio das partículas SDF-1α-DS-CS é 661 ± 8,2 (nm) e a polidispersidade é de 0,23 ± 0,02. O resultado da medição do potencial zeta é mostrado na Figura 2. A partir das cinco medições repetidas, ...

Watch this Scientific Journal Video about Preparation and Characterization of SDF-1Î±-Chitosan-Dextran Sulfate Nanoparticles at JoVE.com

Preparation and Characterization of SDF-1&amp;#945;-Chitosan-Dextran Sulfate Nanoparticles

The objective of this protocol is to incorporate SDF-1&#945;, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1&#945; from the nanoparticles.

Preparação e Caracterização de SDF-1α-Quitosana As nanopartículas de sulfato de dextrano

Chitosan (CS) and dextran sulfate (DS) are charged polysaccharides (glycans), which form polyelectrolyte complex-based nanoparticles when mixed under ...

preparation-characterization-sdf-1-chitosan-dextran-sulfate

Research

JoVE Journal

Chemistry

Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

12.3K visualizações.  Brigham and Women's Hospital and Harvard Medical School. The objective of this protocol is to incorporate SDF-1α, a stem cell homing factor, into dextran sulfate-chitosan nanoparticles. The resultant particles are measured for their size and zeta potential, as well as the content, activity, and in vitro release rate of SDF-1α from the nanoparticles.

Vídeo: Preparation and Characterization of SDF-1&#945;-Chitosan-Dextran Sulfate Nanoparticles

Preparation of Silica Nanoparticles Through Microwave-assisted Acid-catalysis

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle diameters ranging from 30-250 nm by varying the reaction conditions. Through the selection of a microwave compatible solvent, silicic acid precursor, catalyst, and microwave irradiation time, these microwave-assisted methods were capable of overcoming the previously reported shortcomings associated with synthesis of silica nanoparticles using microwave reactors. The siloxane precursor was hydrolyzed using the acid catalyst, HCl. Acetone, a low-tan &#948; solvent, mediates the condensation reactions and has minimal interaction with the electromagnetic field. Condensation reactions begin when the silicic acid precursor couples with the microwave radiation, leading to silica nanoparticle sol formation. The silica nanoparticles were characterized by dynamic light scattering data and scanning electron microscopy, which show the materials&#39; morphology and size to be dependent on the reaction conditions. Microwave-assisted reactions produce silica nanoparticles with roughened textured surfaces that are atypical for silica sols produced by St&#246;ber&#39;s methods, which have smooth surfaces.

Silica nanoparticles were prepared using acid-catalysis of a siloxane precursor and microwave-assisted synthetic techniques resulting in the controlled growth of nanomaterials ranging from 30-250 nm in diameter. The growth dynamics can be controlled by varying the initial silicic acid concentration, time of the reaction, and temperature of reaction.

Microwave-assisted synthetic techniques were used to quickly and reproducibly produce silica nanoparticle sols using an acid catalyst with nanoparticle ...

Química

Preparation and Characterization of Individual and Multi-drug Loaded Physically Entrapped Polymeric Micelles

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar concentration forming hydrophobic cores surrounded by hydrophilic shells in aqueous environments. The core of these micelles can be utilized to load hydrophobic, poorly water soluble drugs like docetaxel (DTX) and everolimus (EVR). Systematic characterization of the micelle structure and drug loading capabilities are important before in vitro and in vivo studies can be conducted. The goal of the protocol described herein is to provide the necessary characterization steps to achieve standardized micellar products. DTX and EVR have intrinsic solubilities of 1.9 and 9.6 &#181;g/ml respectively Preparation of these micelles can be achieved through solvent casting which increases the aqueous solubility of DTX and EVR to 1.86 and 1.85 mg/ml, respectively. Drug stability in micelles evaluated at room temperature over 48 hr indicates that 97% or more of the drugs are retained in solution. Micelle size was assessed using dynamic light scattering and indicated that the size of these micelles was below 50 nm and depended on the molecular weight of the polymer. Drug release from the micelles was assessed using dialysis under sink conditions at pH 7.4 at 37 oC over 48 hr. Curve fitting results indicate that drug release is driven by a first order process indicating that it is diffusion driven.

The goal of this protocol is to describe the preparation and characterization of physically entrapped, poorly water soluble drugs in micellar drug delivery systems composed of amphiphilic block copolymers.

Preparação e caracterização de Individual e Multi-carregadas com droga Fisicamente Entrapped poliméricos Micelles

Amphiphilic block copolymers like polyethyleneglycol-block-polylactic acid (PEG-b-PLA) can self-assemble into micelles above their critical micellar ...

Synthesis, Characterization, and Functionalization of Hybrid Au/CdS and Au/ZnS Core/Shell Nanoparticles

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large extinction coefficients which can be tuned across the visible spectrum. Research into the plasmonic enhancement of optical transitions has become popular, due to the possibility of altering and in some cases improving photo-absorption or emission properties of nearby chromophores such as molecular dyes or quantum dots. The electric field of the plasmon can couple with the excitation dipole of a chromophore, perturbing the electronic states involved in the transition and leading to increased absorption and emission rates. These enhancements can also be negated at close distances by energy transfer mechanism, making the spatial arrangement of the two species critical. Ultimately, enhancement of light harvesting efficiency in plasmonic solar cells could lead to thinner and, therefore, lower cost devices. The development of hybrid core/shell particles could offer a solution to this issue. The addition of a dielectric spacer between a gold nanoparticles and a chromophore is the proposed method to control the exciton plasmon coupling strength and thereby balance losses with the plasmonic gains. A detailed procedure for the coating of gold nanoparticles with CdS and ZnS semiconductor shells is presented. The nanoparticles show high uniformity with size control in both the core gold particles and shell species allowing for a more accurate investigation into the plasmonic enhancement of external chromophores.

The synthesis of uniform gold nanoparticles coated with semiconductor shells of CdS or ZnS is performed. The semiconductor coating is conducted by first depositing a silver sulfide shell and exchanging the silver cations for zinc or cadmium cations.

Síntese, caracterização e funcionalização de híbrida UA / CDS e Au / ZnS Núcleo / Shell Nanopartículas

Plasmonic nanoparticles are an attractive material for light harvesting applications due to their easily modified surface, high surface area and large ...

Synthesis and Characterization of Supramolecular Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical properties for applications in photonics, drug delivery and coating technology. Here we present a new family of colloidal building blocks, coined supramolecular colloids, whose self-assembly is controlled through surface-functionalization with a benzene-1,3,5-tricarboxamide (BTA) derived supramolecular moiety. Such BTAs interact via directional, strong, yet reversible hydrogen-bonds with other identical BTAs. Herein, a protocol is presented that describes how to couple these BTAs to colloids and how to quantify the number of coupling sites, which determines the multivalency of the supramolecular colloids. Light scattering measurements show that the refractive index of the colloids is almost matched with that of the solvent, which strongly reduces the van der Waals forces between the colloids. Before photo-activation, the colloids remain well dispersed, as the BTAs are equipped with a photo-labile group that blocks the formation of hydrogen-bonds. Controlled deprotection with UV-light activates the short-range hydrogen-bonds between the BTAs, which triggers the colloidal self-assembly. The evolution from the dispersed state to the clustered state is monitored by confocal microscopy. These results are further quantified by image analysis with simple routines using ImageJ and Matlab. This merger of supramolecular chemistry and colloidal science offers a direct route towards light- and thermo-responsive colloidal assembly encoded in the surface-grafted monolayer.

A protocol for the synthesis and characterization of colloids coated with supramolecular moieties is described. These supramolecular colloids undergo self-assembly upon the activation of the hydrogen-bonds between the surface-anchored molecules by UV-light.

Síntese e Caracterização de Supramoleculares Colloids

Control over colloidal assembly is of utmost importance for the development of functional colloidal materials with tailored structural and mechanical ...

Sulfate Separation by Selective Crystallization with a Bis-iminoguanidinium Ligand

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, 1,4-benzene-bis(iminoguanidinium) (BBIG), is demonstrated. The ligand is synthesized as the chloride salt (BBIG-Cl) by in situ imine condensation of terephthalaldehyde with aminoguanidinium chloride in water, followed by crystallization as the sulfate salt (BBIG-SO4). Alternatively, BBIG-Cl is synthesized ex situ in larger scale from ethanol. The sulfate separation ability of the BBIG ligand is demonstrated by selective and quantitative crystallization of sulfate from seawater. The ligand can be recycled by neutralization of BBIG-SO4 with aqueous NaOH and crystallization of the neutral bis-iminoguanidine, which can be converted back into BBIG-Cl with aqueous HCl and reused in another separation cycle. Finally, 35S-labeled sulfate and &#946; liquid scintillation counting are employed for monitoring the sulfate concentration in solution. Overall, this protocol will instruct the user in the necessary skills to synthesize a ligand, employ it in the selective crystallization of sulfate from aqueous solutions, and quantify the separation efficiency.

A protocol for in situ aqueous synthesis of a bis(iminoguanidinium) ligand and its utilization in selective separation of sulfate is presented.

Separação sulfato por cristalização selectiva com um ligando bis-iminoguanidinium

A simple and effective method for selective sulfate separation from aqueous solutions by crystallization with a bis-guanidinium ligand, ...

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance imaging (MRI). Their purpose is to enhance the relaxation rate of water protons in tissue, thus increasing the MR image contrast and the specificity of the MRI measurements. Current clinically approved contrast agents are low molecular weight molecules that are rapidly cleared from the body. The use of dendrimers as carriers of paramagnetic chelators can play an important role in the future development of more efficient MRI contrast agents. Specifically, the increase in local concentration of the paramagnetic species results in a higher signal contrast. Furthermore, this CA provides a longer tissue retention time due to its high molecular weight and size. Here, we demonstrate a convenient procedure for the preparation of macromolecular MRI contrast agents based on poly(amidoamine) (PAMAM) dendrimers with monomacrocyclic DOTA-type chelators (DOTA &#8211; 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate). The chelating unit was appended by exploiting the reactivity of the isothiocyanate (NCS) group towards the amine surface groups of the PAMAM dendrimer to form thiourea bridges. Dendrimeric products were purified and analyzed by means of nuclear magnetic resonance spectroscopy, mass spectrometry, and elemental analysis. Finally, high resolution MR images were recorded and the signal contrasts obtained from the prepared dendrimeric and the commercially available monomeric agents were compared.

Preparation and In Vitro Characterization of Dendrimer-based Contrast Agents for Magnetic Resonance Imaging

This protocol describes the preparation and characterization of a dendrimeric magnetic resonance imaging (MRI) contrast agent that carries cyclen-based macrocyclic chelates coordinating paramagnetic gadolinium ions. In a series of MRI experiments in vitro, this agent produced an amplified MRI signal when compared to the commercially available monomeric analogue.

preparação e<em&gt; In Vitro</em&gt; Caracterização de agentes de contraste à base de dendrímeros para Ressonância Magnética

Paramagnetic complexes of gadolinium(III) with acyclic or macrocyclic chelates are the most commonly used contrast agents (CAs) for magnetic resonance ...

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 ...

Ligand-Mediated Nucleation and Growth of Palladium Metal Nanoparticles

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution of capping ligands during the synthesis reaction, their role in regulating the nucleation and growth rates of colloidal nanoparticles is not well understood. In this work, we demonstrate a mechanistic investigation of the role of trioctylphosphine (TOP) in Pd nanoparticles in different solvents (toluene and pyridine) using in situ SAXS and ligand-based kinetic modeling. Our results under different synthetic conditions reveal the overlap of nucleation and growth of Pd nanoparticles during the reaction, which contradicts the LaMer-type nucleation and growth model. The model accounts for the kinetics of Pd-TOP binding for both, the precursor and the particle surface, which is essential to capture the size evolution as well as the concentration of particles in situ. In addition, we illustrate the predictive power of our ligand-based model through designing the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can be applied to other synthesis systems and therefore serves as an effective strategy for predictive synthesis of colloidal nanoparticles.

The main goal of this work is to elucidate the role of capping agents in regulating the size of palladium nanoparticles by combining in situ small angle x-ray scattering (SAXS) and ligand-based kinetic modeling.

Nucleação e Crescimento Mediado por Ligante de Nanopartículas de Paládio Metálico

The size, size distribution and stability of colloidal nanoparticles are greatly affected by the presence of capping ligands. Despite the key contribution ...

High Resolution Physical Characterization of Single Metallic Nanoparticles

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single nanometer-scale pore. The signal is characteristic of the molecule&#39;s physicochemical properties and its interactions with the pore. We demonstrate that the nanopore formed by the bacterial protein exotoxin Staphylococcus aureus alpha hemolysin (&#945;HL) can detect polyoxometalates (POMs, anionic metal oxygen clusters), at the single molecule limit. Moreover, multiple degradation products of 12-phosphotungstic acid POM (PTA, H3PW12O40) in solution are simultaneously measured. The single molecule sensitivity of the nanopore method allows for POMs to be characterized at significantly lower concentrations than required for nuclear magnetic resonance (NMR) spectroscopy. This technique could serve as a new tool for chemists to study the molecular properties of polyoxometalates or other metallic clusters, to better understand POM synthetic processes, and possibly improve their yield. Hypothetically, the location of a given atom, or the rotation of a fragment in the molecule, and the metal oxidation state could be investigated with this method. In addition, this new technique has the advantage of allowing the real-time monitoring of molecules in solution.&#160;

Here, we present a protocol to detect discrete metal oxygen clusters, polyoxometalates (POMs), at the single molecule limit using a biological nanopore-based electronic platform. The method provides a complementary approach to traditional analytical chemistry tools used in the study of these molecules.

Caracterização física de alta resolução de nanopartículas metálicas únicas

Individual molecules can be detected and characterized by measuring the degree by which they reduce the ionic current flowing through a single ...

Synthesis and Characterization of Amphiphilic Gold Nanoparticles

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of their interactions with cell membranes, lipid bilayers, and viruses. The hydrophilic ligands make these particles colloidally stable in aqueous solutions and the combination with hydrophobic ligands creates an amphiphilic particle that can be loaded with hydrophobic drugs, fuse with the lipid membranes, and resist nonspecific protein adsorption. Many of these properties depend on nanoparticle size and the composition of the ligand shell. It is, therefore, crucial to have a reproducible synthetic method and reliable characterization techniques that allow the determination of nanoparticle properties and the ligand shell composition. Here, a one-phase chemical reduction, followed by a thorough purification to synthesize these nanoparticles with diameters below 5 nm, is presented. The ratio between the two ligands on the surface of the nanoparticle can be tuned through their stoichiometric ratio used during synthesis. We demonstrate how various routine techniques, such as transmission electron microscopy (TEM), nuclear magnetic resonance (NMR), thermogravimetric analysis (TGA), and ultraviolet-visible (UV-Vis) spectrometry, are combined to comprehensively characterize the physicochemical parameters of the nanoparticles.

Amphiphilic gold nanoparticles can be used in many biological applications. A protocol to synthesize gold nanoparticles coated by a binary mixture of ligands and a detailed characterization of these particles is presented.

Síntese e caracterização de nanopartículas de ouro Anfífilos

Gold nanoparticles covered with a mixture of 1-octanethiol (OT) and 11-mercapto-1-undecane sulfonic acid (MUS) have been extensively studied because of ...