Agradecemos al Prof. JP Spatz (Departamento de Química Biofísica, Universidad de Heidelberg y el Departamento de Nuevos Materiales y Biosystems, Instituto Max Planck para Sistemas Inteligentes, Stuttgart) por su amable apoyo. El apoyo financiero de la Max-Planck-Gesellschaft y la Deutsche Forschungsgemeinschaft (DFG SFB/TR79 a EAC-A.) También se reconoce en gran medida.

1. Síntesis de 11-Mercaptoundecanoyl-N-hidroxisuccinimida éster (MU-NHS) <ol><li> Añadir gota a gota una solución de 500 mg de N-hidroxisuccinimida y 30 mg de 4 - (dimetilamino) piridina en 10 ml de acetona (PA) a 1 g de ácido 11-mercaptoundecanoico en 40 ml de diclorometano (PA) a temperatura ambiente (RT). </li><li> Enfriar la reacción a 0 ° C y añadir gota a gota 1,1 g de N, N &#39;-diciclohexilcarbodiimida en 10 ml de diclorometano (bajo atmósfera de nitrógeno). Mantener la reacción a baja temperatura durante 1 hora y después se agita a TA durante la noche. </li><li> Se filtra el precipitado y se seca a presión reducida. El producto se purifica mediante cromatografía flash con benceno petróleo y acetato de etilo (pa) en una proporción de 1:1. </li></ol> 2. Preparación de capas de oro homogéneos <ol><li> Cubreobjetos de vidrio limpias con toallitas de precisión y sonicar ellos durante 5 minutos en una solución que contiene una mezcla 1:1 de acetato de etilo (pa) y metanol (pa). Rinse sustratos con metanol y se secan bajo flujo de nitrógeno. </li><li> Coloca los sustratos limpios en el dispositivo de revestimiento por bombardeo iónico. Evacuar la cámara. Retire la capa de óxido de cromo superior de la meta de cromo mediante pulverización durante 60 segundos. Colocar las muestras por debajo de la viga de metal y recubrirlos con una capa de cromo de 10 nm, seguido por recubrimiento con una capa de oro de 40 nm. </li></ol> 3. Inmovilización de la superficie de la BMP-2 <ol><li> Disolver MU-NHS en N, N-dimethlyformamide (DMF) a una concentración final de aproximadamente 1 mM y se incuba sustratos de oro en la solución MU-NHS a TA durante 4 h bajo atmósfera de nitrógeno. </li><li> Superficies Someter a ultrasonidos en DMF durante 2 min, enjuague con DMF y MeOH y se secan bajo flujo de nitrógeno. </li><li> Preparar una solución madre de rhBMP-2 en HCl 4 mM estéril con una concentración de 100 g / ml (almacenar alícuotas a -80 ° C). Para diluciones de trabajo (3,5 mg / ml), se diluye la solución madre en PBS / NaCl (PBS que contenía 1 M de NaCl) y unJUSTE a pH 8,5 inmediatamente antes del uso. </li><li> Incubar superficies funcionalizadas MU-NHS en la solución de trabajo de rhBMP-2 a 4 ° C durante la noche. Aspirar el sobrenadante de la incubación. Superficies Sonicar en PBS / NaCl durante 2 minutos y se lavan 3 veces con PBS estéril / NaCl. </li></ol> 4. Caracterización de superficies <ol><li> Para bloquear la adsorción no específica del anticuerpo, se incuban las superficies con un 5% de BSA (w / v) en solución de PBS durante 1 hora a TA, seguido de incubación con un anticuerpo anti-BMP-2 (1:100 en 1% (w / v ) solución de BSA / PBS) durante 1 hora a TA. Lave las superficies dos veces con PBS y déjelos en remojo durante 30 seg. </li><li> Incubar sustratos con anticuerpo secundario conjugado con HRP (1:1000 en 1% (w / v) de solución de BSA / PBS) durante 30 min a TA, a continuación, lavar dos veces con PBS. </li><li> Utilice ensayo de rojo Ampliflu para medir la actividad enzimática de HRP a 570 nm con un lector de placas. </li></ol> 5. Análisis de la Actividad Biológica <ol><li> Seed 1 x 10 5 ratón mioblastos C2C12 por pocillo en 6 pocillos plAtes en medio de crecimiento, que consisten en un DMEM de alta glucosa que contenía piruvato suplementado con 10% de FBS, 1% de penicilina / estreptomicina y se incuba durante 24 horas a 37 ° C / 5% de CO 2. </li><li> Morir de hambre las células en DMEM libre de suero durante 3-5 horas antes de la siembra en las superficies decoradas con inmovilizada BMP-2. </li><li> Para la investigación de la inducción de la señalización de corto plazo, sustituir el medio por 200 l DMEM libre de suero y colocar los inmovilizados BMP-2 superficies superiores a las células. La superficie debe ser manejado con pinzas de punta fina para evitar que se raye. </li><li> Retire suavemente las superficies y aspirar el medio con una pipeta, se lavan las células dos veces con PBS. Continúe con el análisis de las respuestas de células. </li><li> Para el análisis de la actividad biológica a largo plazo, células de la placa en las superficies y la cultura ellos a 37 ° C / 5% de CO 2 en condiciones de suero bajas (2% de FBS) durante seis días. </li></ol>

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En este protocolo se describe la preparación de superficies funcionalizadas con rhBMP-2 bioactivo. Este enfoque comprende dos etapas: 1) la formación inicial de una monocapa auto-montaje (SAM) de un conector bifuncional en la superficie de oro, 2) la inmovilización covalente de la proteína rhBMP-2. En trabajos anteriores, hemos validado la unión efectiva del enlazador bifuncional y el factor de crecimiento, y demostramos que superficie inmovilizada rhBMP-2 mantiene su actividad biológica 19. La bioactiv...

Proteína morfogenética ósea 2 (BMP-2) es un miembro del factor de crecimiento transformante (TGF-β) de la familia y actúa como inductor de la formación de novo de hueso, así como regulador de varios tejidos durante el desarrollo embrionario y adulto homeostasis 1-3. Cada monómero de la proteína biológicamente activa homodimérica BMP-2 contiene un motivo de &quot;nudo de cisteína&quot;, que está altamente conservada en todas las BMP 4. Seis de los siete residuos de cisteína forman enlaces disulfuro intramoleculares que estabilizan cada monómero, mientras que la séptima cisteína está involucrado en la dimerización, formando un enlace intermolecular entre los dos monómeros 5,6. Este nudo de cisteína altamente conservados define la estructura tridimensional de la proteína BMP-2 y determina sus propiedades únicas, tales como resistencia al calor, desnaturalizantes y ácida de pH 7-9. BMP-2 se une a receptores transmembrana quinasa serina / treonina, induciendo de este modo la transducción de señales <sup&gt; 10-12. Dependiendo del modo de oligomerización del receptor, diferentes vías de señalización se activan: una cascada de señalización Smad-independiente conduce a la inducción de la fosfatasa alcalina a través de señalización de p38, mientras que una vía de Smad-dependiente activado por resultados de fosforilación del receptor de Smad en la translocación nuclear complejo y la activación de la transcripción de genes diana específicos, tales como el inhibidor de la diferenciación (Id) 12-14. En el hueso, BMP-2 induce la diferenciación de células madre mesenquimales en osteoblastos, estimulando así la curación y la formación de novo de hueso. Actualmente, expresada de forma recombinante BMP-2 se aplica clínicamente para mejorar la curación de los sitios fracturados. Una estrategia común en ingeniería de tejido óseo es el uso de factores de crecimiento inyectables, que es menos invasiva en comparación con los sistemas de suministro locales. Sin embargo, estudios in vivo y aplicaciones clínicas han demostrado que la vida media biológica corta, loc inespecíficazación y rápida de domiciliación de BMP-2 puede dar lugar a varios problemas locales, ectópicos y sistémicos 15. Por lo tanto, para obtener una presentación eficaz, el atrapamiento o la inmovilización de la BMP-2 dentro o sobre materiales es necesario para su entrega local y sostenida en el sitio diana. La liberación sostenida se puede lograr con los enfoques de retención no covalentes, tales como atrapamiento físico, adsorción o de iones complejación 16. Sin embargo, se sabe que la adsorción no específica de proteínas a superficies puede resultados en la desnaturalización de las moléculas 17. Para la unión de factores de crecimiento covalente, diferentes tipos de soportes se han desarrollado en la última década. El uso de moléculas de unión bifuncional que se dirigen a grupos amino o carboxilo de la proteína, por ejemplo, es un tipo de enfoque que no requiere necesariamente la modificación de proteínas para lograr su inmovilización. De hecho, mientras que la modificación de proteínas ofrece la ventaja de controlar la orientación de proteína,la introducción de dominios artificiales, etiquetas de péptidos y cadenas específicas de sitio puede alterar la actividad biológica de factores de crecimiento 17. Por lo tanto, para eludir la desnaturalización debida a la interacción con el material de apoyo, las superficies se pueden funcionalizar de antemano, por ejemplo, con una capa monomolecular auto-ensamblada (SAM) de una molécula de unión, seguido por acoplamiento del factor deseado 18. Hemos utilizado un enfoque basado en el SAM para inmovilizar covalentemente BMP-2 en una superficie por la orientación de sus residuos amino libres y hemos demostrado que la proteína inmovilizada conserva tanto su actividad biológica a corto y largo plazo 19. Este protocolo proporciona una forma simple y eficiente para entregar BMP-2 a las células para estudios in vitro de los mecanismos que se producen en la membrana celular y regulan la señalización intracelular responsable de la señalización de osteogénico.

<table border="1">
	<tbody>
		<tr>
			<td>Name of Material/ Equipment</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr>
			<td>N-hydroxysuccinimide</td>
			<td>Sigma-Aldrich</td>
			<td>130672</td>
			<td></td>
		</tr>
		<tr>
			<td>4-(dimethylamino)pyridin</td>
			<td>Sigma-Aldrich</td>
			<td>522805</td>
			<td></td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>AppliChem</td>
			<td>A2282</td>
			<td></td>
		</tr>
		<tr>
			<td>11-mercaptoundecanoic acid</td>
			<td>Sigma-Aldrich</td>
			<td>674427</td>
			<td></td>
		</tr>
		<tr>
			<td>Dichlormethane</td>
			<td>Merck</td>
			<td>106050</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N&#39;-dicyclohexylcarbodiimide</td>
			<td>Sigma-Aldrich</td>
			<td>D80002</td>
			<td></td>
		</tr>
		<tr>
			<td>Petroleum benzene</td>
			<td>Merck</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Glass coverslips</td>
			<td>Carl Roth</td>
			<td>M 875</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylacetate</td>
			<td>AppliChem</td>
			<td>A3550</td>
			<td></td>
		</tr>
		<tr>
			<td>Methanol</td>
			<td>Carl Roth</td>
			<td>4627</td>
			<td></td>
		</tr>
		<tr>
			<td>N,N-dimethylformamide</td>
			<td>Carl Roth</td>
			<td>T921</td>
			<td></td>
		</tr>
		<tr>
			<td>rhBMP-2</td>
			<td>R&#38;D Systems</td>
			<td>355-BM</td>
			<td>Carrier-free; expressed in E.coli</td>
		</tr>
		<tr>
			<td>PBS</td>
			<td>PAA</td>
			<td>H15-002</td>
			<td></td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Carl Roth</td>
			<td>HN00.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly(dimethyl siloxane) (PDMS)</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sylgard 184 silicone elastomer kit</td>
			<td>Dow Corning</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Anti-rhBMP-2</td>
			<td>Sigma</td>
			<td>B9553</td>
			<td></td>
		</tr>
		<tr>
			<td>Goat anti-mouse IgG-HRP</td>
			<td>Santa Cruz</td>
			<td>sc-2005</td>
			<td>Secondary antibody</td>
		</tr>
		<tr>
			<td>Ampliflu Red assay</td>
			<td>Sigma</td>
			<td>90101</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM) (1x), liquid</td>
			<td>Gibco</td>
			<td>41966</td>
			<td>High glucose</td>
		</tr>
		<tr>
			<td>Fetal Bovine Serum (FBS)</td>
			<td>Sigma</td>
			<td>F7524</td>
			<td>Sterile filtered, cell culture tested</td>
		</tr>
		<tr>
			<td>Pen/Strep</td>
			<td>Gibco</td>
			<td>15140</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin 0.05% (1x) with EDTA 4Na</td>
			<td>Gibco</td>
			<td>25300</td>
			<td></td>
		</tr>
		<tr>
			<td>Glycine (0.1 M)</td>
			<td>Riedel-de Ha&#235;n</td>
			<td>33226</td>
			<td></td>
		</tr>
		<tr>
			<td>IGEPAL CA-630 (1%)</td>
			<td>Sigma</td>
			<td>I8896</td>
			<td>Lysis buffer (ALP assay)19</td>
		</tr>
		<tr>
			<td>Magnesium chloride (MgCl2)(1 mM)</td>
			<td>Carl Roth</td>
			<td>HNO3.2</td>
			<td></td>
		</tr>
		<tr>
			<td>Zinc chloride (ZnCl2) (1 mM)</td>
			<td>Carl Roth</td>
			<td>3533.1</td>
			<td></td>
		</tr>
		<tr>
			<td>p-nitrophenylphosphate (pNPP)</td>
			<td>Sigma</td>
			<td>S0942</td>
			<td>Phosphatase substrate</td>
		</tr>
		<tr>
			<td>Anti-mysin heavy chain (MHC)</td>
			<td>Developmental Studies Hybridoma Bank, University of Iowa</td>
			<td>MF20</td>
			<td>Monoclonal antibody</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 Goat anti-mouse IgG</td>
			<td>Invitrogen</td>
			<td>A11001</td>
			<td></td>
		</tr>
		<tr>
			<td>DAPI</td>
			<td>Sigma</td>
			<td>D9542</td>
			<td></td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Equipment</td>
		</tr>
		<tr>
			<td>Ultrsonic bath (Sonorex Super RK 102H), Frequency 35 kHz</td>
			<td>BANDELIN electronic GmbH &#38; Co. KG</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>MED 020 Sputtercoating system</td>
			<td>BAL-TEC AG</td>
			<td></td>
			<td>Coating conditions 
			Cr: 120 mA, 1.3 x 10-2 mbar, 30 sec 
			Au: 60 mA, 5.0 x 10-2 mbar, 45 sec</td>
		</tr>
		<tr>
			<td>Tecan Infinite M200 Plate reader</td>
			<td>Tecan</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

covalent binding of bmp-2 on surfaces using a self-assembled monolayer approach

Proteína morfogenética ósea 2 (BMP-2) es un factor de crecimiento embebido en la matriz extracelular del tejido óseo. BMP-2 actúa como desencadenante de la diferenciación de células mesenquimales en osteoblastos, estimulando así la cicatrización y la formación de hueso novo. El uso clínico de la humana recombinante BMP-2 (rhBMP-2), en relación con los andamios ha suscitado controversias recientes, en base a la forma de presentación y la cantidad que se va a entregar. El protocolo presentado aquí proporciona una forma simple y eficiente para entregar BMP-2 para los estudios in vitro sobre las células. Describimos cómo formar una monocapa auto-ensamblado que consiste en un engarce heterobifuncional, y mostramos el paso de unión posterior para obtener la inmovilización covalente de rhBMP-2. Con este enfoque es posible lograr una presentación sostenida de BMP-2, mientras que el mantenimiento de la actividad biológica de la proteína. De hecho, la inmovilización de superficie de BMP-2 permite que las investigaciones dirigidas por la prevención de anuncios inespecíficosdesorción, mientras que la reducción de la cantidad de factor de crecimiento y, más notablemente, lo que dificulta la liberación no controlada de la superficie. Ambos eventos de señalización de corto y largo plazo provocados por BMP-2 se llevan a cabo cuando las células están expuestas a las superficies que presentan inmovilizado covalentemente rhBMP-2, por lo que este enfoque adecuado para los estudios in vitro sobre las respuestas celulares a BMP-2 estimulación.

En nuestra configuración, el oro fue elegido como excipiente, ya que proporciona un sistema biológico no específico pero químicamente sintonizable. Además, la aplicación de las monocapas de autoensamblaje implica muchos beneficios: SAM adsorber de forma espontánea a través de sus &quot;cabeza-grupos&quot; en metales y forman monocapas con pocos defectos, mientras que sus grupos terminales funcionales se pueden modificar adicionalmente. Por tanto, proporcionan una plataforma para adaptar las propiedades de la int...

Watch this Scientific Journal Video about Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach at JoVE.com

Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

Se describe un método para llevar a cabo la inmovilización eficaz de BMP-2 en las superficies. Nuestro enfoque se basa en la formación de una capa monomolecular auto-ensamblada para lograr la unión de BMP-2 a través de sus residuos de amina libres covalente. Este método es una herramienta útil para el estudio de señalización en la membrana celular.

Unión covalente de BMP-2 en las superficies utilizando una monocapa enfoque de auto-ensamblada

Bone morphogenetic protein 2 (BMP-2) is a growth factor embedded in the extracellular matrix of bone tissue. BMP-2 acts as trigger of mesenchymal cell ...

covalent-binding-bmp-2-on-surfaces-using-self-assembled-monolayer

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Education

JoVE Journal

JoVE Core

Organic Chemistry

Chemistry

Unit 1

Covalent Bonding and Structure

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13.8K vistas.  University of Heidelberg.  Se describe un método para llevar a cabo la inmovilización eficaz de BMP-2 en las superficies. Nuestro enfoque se basa en la formación de una capa monomolecular auto-ensamblada para lograr la unión de BMP-2 a través de sus residuos de amina libres covalente. Este método es una herramienta útil para el estudio de señalización en la membrana celular. 

Video: Covalent Binding of BMP-2 on Surfaces Using a Self-assembled Monolayer Approach

Stabilizing Hepatocellular Phenotype Using Optimized Synthetic Surfaces

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing and maintaining primary and pluripotent stem cell derived hepatocytes. While biological matrices are useful, they permit short term culture of hepatocytes, limiting their widespread application. We have attempted to overcome the limitations using a synthetic polymer coating. Polymers represent one of the broadest classes of biomaterials and possess a wide range of mechanical, physical and chemical properties, which can be fine-tuned for purpose. Importantly, such materials can be scaled to quality assured standards and display batch-to-batch consistency. This is essential if cells are to be expanded for high through-put screening in the pharmaceutical testing industry or for cellular based therapy. Polyurethanes (PUs) are one group of materials that have shown promise in cell culture. Our recent progress in optimizing a polyurethane coated surface, for long-term culture of human hepatocytes displaying stable phenotype, is presented and discussed.

This article will focus on developing polymer coated surfaces for long-term, stable culture of stem cell derived human hepatocytes.

Estabilizar hepatocelular Fenotipo Usando superficies sintéticas optimizadas

Currently, one of the major limitations in cell biology is maintaining differentiated cell phenotype. Biological matrices are commonly used for culturing ...

Investigación

Química

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.

In this paper, a procedure for quantifying the mass transport parameters of chemicals in various materials is presented. This process involves employing an inverse-analysis based diffusion model to vapor emission profiles recorded by real-time, mass spectrometry in high vacuum.

Un enfoque de análisis inverso a la caracterización de Transporte de Productos Químicos en Pinturas

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in ...

Facile Preparation of Internally Self-assembled Lipid Particles Stabilized by Carbon Nanotubes

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled (functionalized) CNTs are used as stabilizers to produce Pickering type oil-in-water (O/W) emulsions. Lipids namely, Dimodan U and Phytantriol are used as emulsifiers, which in excess water self-assemble into the bicontinuous cubic Pn3m phase. This highly viscous phase is fragmented into smaller particles using a probe ultrasonicator in presence of conventional surfactant stabilizers or CNTs as done here. Initially, the CNTs (powder form) are dispersed in water followed by further ultrasonication with the molten lipid to form the final emulsion. During this process the CNTs get coated with lipid molecules, which in turn are presumed to surround the lipid droplets to form a particulate emulsion that is stable for months. The average size of CNT-stabilized nanostructured lipid particles is in the submicron range, which compares well with the particles stabilized using conventional surfactants. Small angle X-ray scattering data confirms the retention of the original Pn3m cubic phase in the CNT-stabilized lipid dispersions as compared to the pure lipid phase (bulk state). Blue shift and lowering of the intensities in characteristic G and G&#39; bands of CNTs observed in Raman spectroscopy characterize the interaction between CNT surface and lipid molecules. These results suggest that the interactions between the CNTs and lipids are responsible for their mutual stabilization in aqueous solutions. As the concentrations of CNTs employed for stabilization are very low and lipid molecules are able to functionalize the CNTs, the toxicity of CNTs is expected to be insignificant while their biocompatibility is greatly enhanced. Hence the present approach finds a great potential in various biomedical applications, for instance, for developing hybrid nanocarrier systems for the delivery of multiple functional molecules as in combination therapy or polytherapy.

We report on a smart application of carbon nanotubes for kinetic stabilization of lipid particles that contain self-assembled nanostructures in their cores. The preparation of lipid particles requires rather low concentrations of carbon nanotubes permitting their use in biomedical applications such as drug delivery.

Preparación fácil del ensamblado autónomos Internamente Lípidos Las partículas estabilizadas por nanotubos de carbono

We present a facile method to prepare nanostructured lipid particles stabilized by carbon nanotubes (CNTs). Single-walled (pristine) and multi-walled ...

Highly Stable, Functional Hairy Nanoparticles and Biopolymers from Wood Fibers: Towards Sustainable Nanotechnology

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While metal-based nanoparticles are associated with synthetic and environmental hassles, cellulose introduces a green, sustainable alternative for nanoparticle synthesis. Here, we present the chemical synthesis and separation procedures to produce new classes of hairy nanoparticles (bearing both amorphous and crystalline regions) and biopolymers based on wood fibers. Through periodate oxidation of soft wood pulp, the glucose ring of cellulose is opened at the C2-C3 bond to form 2,3-dialdehyde groups. Further heating of the partially oxidized fibers (e.g., T = 80 &#176;C) results in three products, namely fibrous oxidized cellulose, sterically stabilized nanocrystalline cellulose (SNCC), and dissolved dialdehyde modified cellulose (DAMC), which are well separated by intermittent centrifugation and co-solvent addition. The partially oxidized fibers (without heating) were used as a highly reactive intermediate to react with chlorite for converting almost all aldehyde to carboxyl groups. Co-solvent precipitation and centrifugation resulted in electrosterically stabilized nanocrystalline cellulose (ENCC) and dicarboxylated cellulose (DCC). The aldehyde content of SNCC and consequently surface charge of ENCC (carboxyl content) were precisely controlled by controlling the periodate oxidation reaction time, resulting in highly stable nanoparticles bearing more than 7 mmol functional groups per gram of nanoparticles (e.g., as compared to conventional NCC bearing &#60;&#60; 1 mmol functional group/g). Atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) attested to the rod-like morphology. Conductometric titration, Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), dynamic light scattering (DLS), electrokinetic-sonic-amplitude (ESA) and acoustic attenuation spectroscopy shed light on the superior properties of these nanomaterials.

Synthesis schemes to prepare highly stable wood fiber-based hairy nanoparticles and functional cellulose-based biopolymers have been detailed.

Altamente estable, funcional Hairy nanopartículas y biopolímeros con fibras de madera: Hacia Nanotecnología Sostenible

Nanoparticles, as one of the key materials in nanotechnology and nanomedicine, have gained significant importance during the past decade. While ...

Microfluidic-based Synthesis of Covalent Organic Frameworks (COFs): A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The first COF was reported in 2005 with much effort centered on the establishment of new synthetic routes for its preparation. To date, most available synthetic methods for COF synthesis are based on bulk mixing under solvothermal conditions. Therefore, there is increasing interest in developing systematic protocols for COF synthesis that provide for fine control over reaction conditions and improve COF processability on surfaces, which is essential for their use in practical applications. Herein, we present a novel microfluidic-based method for COF synthesis where the reaction between two constituent building blocks, 1,3,5-benzenetricarbaldehyde (BTCA) and 1,3,5-tris(4-aminophenyl)benzene (TAPB), takes place under controlled diffusion conditions and at room temperature. Using such an approach yields sponge-like, crystalline fibers of a COF material, hereafter called MF-COF. The mechanical properties of MF-COF and the dynamic nature of the approach allow the continuous production of MF-COF fibers and their direct printing onto surfaces. The general method opens new potential applications requiring advanced printing of 2D or 3D COF structures on flexible or rigid surfaces.

Microfluidic-based Synthesis of Covalent Organic Frameworks COFs: A Tool for Continuous Production of COF Fibers and Direct Printing on a Surface

We present a novel microfluidic-based method for synthesis of covalent organic frameworks (COFs). We demonstrate how this approach can be used to produce continuous COF fibers, and also 2D or 3D COF structures on surfaces.

Síntesis microfluídica de marcos orgánicos covalentes (COFs): Una herramienta para la producción continua de fibras COF e impresión directa en una superficie

Covalent Organic Frameworks (COFs) are a class of porous covalent materials which are frequently synthesized as unprocessable crystalline powders. The ...

Light-driven Molecular Motors on Surfaces for Single Molecular Imaging

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces are demonstrated. This work requires careful design, considerable synthetic effort, and proper analysis. The rotary motion of the molecular motor in solution is shown by 1H NMR and UV-vis absorption spectroscopy techniques. In addition, the method to graft the motor onto an amine-coated quartz is described. This method helps to gain more insight into molecular machines.

The manuscript describes how to synthesize and graft a molecular motor on surfaces for single molecular imaging.

Motores moleculares basadas en la luz en superficies para la proyección de imagen Molecular solo

The design and synthesis of a synthetic system that aims for the direct visualization of a synthetic rotary motor at the single molecule level on surfaces ...

Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry

Desorption/Ionization Induced by Neutral SO2 Clusters (DINeC) is employed as a very soft and efficient desorption/ionization technique for mass spectrometry (MS) of complex molecules and their reactions on surfaces. DINeC is based on a beam of SO2 clusters impacting on the sample surface at low cluster energy. During cluster-surface impact, some of the surface molecules are desorbed and ionized via dissolvation in the impacting cluster; as a result of this dissolvation-mediated desorption mechanism, low cluster energy is sufficient and the desorption process is extremely soft. Both surface adsorbates and molecules of which the surface is composed of can be analyzed. Clear and fragmentation-free spectra from complex molecules such as peptides and proteins are obtained. DINeC does not require any special sample preparation, in particular no matrix has to be applied. The method yields quantitative information on the composition of the samples; molecules at a surface coverage as low as 0.1 % of a monolayer can be detected. Surface reactions such as H/D exchange or thermal decomposition can be observed in real-time and the kinetics of the reactions can be deduced. Using a pulsed nozzle for cluster beam generation, DINeC can be efficiently combined with ion trap mass spectrometry. The matrix-free and soft nature of the DINeC process in combination with the MSn capabilities of the ion trap allows for very detailed and unambiguous analysis of the chemical composition of complex organic samples and organic adsorbates on surfaces.

Neutral SO2 clusters of low kinetic energy (&#60; 0.8 eV/constituent) are used to desorb complex surface molecules such as peptides or lipids for further analysis by means of mass spectrometry using an ion trap mass spectrometer. No special sample preparation is required, and real-time observation of reactions is possible.

Análisis de moléculas complejas y sus reacciones en superficies por medios de espectrometría de masas de desorción/ionización inducida por racimos

Desorption/Ionization Induced by Neutral SO2 Clusters (DINeC) is employed as a very soft and efficient desorption/ionization technique for mass ...

Covalent Attachment of Single Molecules for AFM-based Force Spectroscopy

Atomic force microscopy (AFM)-based single molecule force spectroscopy is an ideal tool for investigating the interactions between a single polymer and surfaces. For a true single molecule experiment, covalent attachment of the probe molecule is essential because only then can hundreds of force-extension traces with one and the same single molecule be obtained. Many traces are in turn necessary to prove that a single molecule alone is probed. Additionally, passivation is crucial for preventing unwanted interactions between the single probe molecule and the AFM cantilever tip as well as between the AFM cantilever tip and the underlying surface. The functionalization protocol presented here is reliable and can easily be applied to a variety of polymers. Characteristic single molecule events (i.e., stretches and plateaus) are detected in the force-extension traces. From these events, physical parameters such as stretching force, desorption force and desorption length can be obtained. This is particularly important for the precise investigation of stimuli-responsive systems at the single molecule level. As exemplary systems poly(ethylene glycol) (PEG), poly(N-isopropylacrylamide) (PNiPAM) and polystyrene (PS) are stretched and desorbed from SiOx (for PEG and PNiPAM) and from hydrophobic self-assembled monolayer surfaces (for PS) in aqueous environment.

Covalent attachment of probe molecules to atomic force microscopy (AFM) cantilever tips is an essential technique for the investigation of their physical properties. This allows us to determine the stretching force, desorption force and length of polymers via AFM-based single molecule force spectroscopy with high reproducibility.

Adjunto covalente de moléculas únicas para espectroscopia de fuerza basada en AFM

Atomic force microscopy (AFM)-based single molecule force spectroscopy is an ideal tool for investigating the interactions between a single polymer and ...

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach

Methine-bridged conjugated bicyclic aromatic compounds are common constituents of a range of biologically relevant molecules such as porphyrins, dipyrrinones, and pharmaceuticals. Additionally, restricted rotation of these systems often results in highly to moderately fluorescent systems as observed in 3H,5H-dipyrrolo[1,2-c:2',1'-f]pyrimidin-3-ones, xanthoglows, pyrroloindolizinedione analogs, BODIPY analogs, and the phenolic and imidazolinone ring systems of Green Fluorescent Protein (GFP). This manuscript describes an inexpensive and operationally simple method of performing a Claisen-Schmidt condensation to generate a series of fluorescent pH dependent pyrazole/imidazole/isoindolone dipyrrinone analogs. While the methodology illustrates the synthesis of dipyrrinone analogs, it can be translated to produce a wide range of conjugated bicyclic aromatic compounds. The Claisen-Schmidt condensation reaction utilized in this method is limited in scope to nucleophiles and electrophiles that are enolizable under basic conditions (nucleophile component) and non-enolizable aldehydes (electrophile component). Additionally, both the nucleophilic and electrophilic reactants must contain functional groups that will not inadvertently react with hydroxide. Despite these limitations, this methodology offers access to completely novel systems that can be employed as biological or molecular probes.

The Claisen-Schmidt condensation reaction is an important methodology for the generation of methine-bridged conjugated bicyclic aromatic compounds. Through utilizing a base-mediated variant of the aldol reaction, a range of fluorescent and/or biologically relevant molecules can be accessed through a generally inexpensive and operationally simple synthetic approach.

Síntesis De Pirazol Dependiente De pH, Imidazol, Y Fluoróforos De Isoindolona Dipirorina Usando Un Enfoque De Condensación De Claisen-Schmidt

Methine-bridged conjugated bicyclic aromatic compounds are common constituents of a range of biologically relevant molecules such as porphyrins, ...

Analysis of Organochlorine Pesticides in a Soil Sample by a Modified QuEChERS Approach Using Ammonium Formate

Currently, the QuEChERS method represents the most widely used sample preparation protocol worldwide for analyzing pesticide residues in a broad variety of matrices both in official and non-official laboratories. The QuEChERS method using ammonium formate has previously proven to be advantageous compared to the original and the two official versions. On the one hand, the simple addition of 0.5 g of ammonium formate per gram of sample is sufficient to induce phase separation and achieve good analytical performance. On the other hand, ammonium formate reduces the need for maintenance in routine analyses. Here, a modified QuEChERS method using ammonium formate was applied for the simultaneous analysis of organochlorine pesticide (OCP) residues in agricultural soil. Specifically, 10 g of the sample was hydrated with 10 mL of water and then extracted with 10 mL of acetonitrile. Next, phase separation was carried out using 5 g of ammonium formate. After centrifugation, the supernatant was subjected to a dispersive solid-phase extraction clean-up step with anhydrous magnesium sulfate, primary-secondary amine, and octadecylsilane. Gas chromatography-mass spectrometry was used as the analytical technique. The QuEChERS method using ammonium formate is demonstrated as a successful alternative for extracting OCP residues from a soil sample.

The present protocol describes the utilization of ammonium formate for phase partitioning in QuEChERS, together with gas chromatography-mass spectrometry, to successfully determine organochlorine pesticide residues in a soil sample.

Análisis de plaguicidas organoclorados en una muestra de suelo mediante un enfoque QuEChERS modificado utilizando formiato de amonio

Currently, the QuEChERS method represents the most widely used sample preparation protocol worldwide for analyzing pesticide residues in a broad variety ...