Nanobots para combatir el cáncer

Científicos del Wyss Institute for Biologically Inspired Engineering de Harvard han creado robots a partir del ADN que podrían combatir diversas enfermedades algún día. Estos robots hechos en nano escala (como se puede inferir por el título de esta publicación) podrían ser usados para dar instrucciones directamente a las células del paciente. Con esta técnica se podrían combatir diferentes enfermedades y hacer que las células cancerígenas se maten a sí mismas. Los robotcitos están construidos usando la técnica del Origami de ADN (leer abajo).

En este caso, el ADN fue diseñado para operar en un simple sistema de lógica, como una computadora. Tiene la forma de un barril, con dos partes del mismo separadas por una bisagra. Diferentes químicos se pueden introducir dentro del robot. Luego, cuando encuentra la molécula particular por la que fue diseñada –como una proteína que solo se encuentra en una célula cancerígena- activa un switch que abre el barril y libera el químico que lleva dentro.

El Dr. Ido Bachalet dijo en un comunicado de prensa  “Se puede pensar en una clase de combinación de apertura, solo cuando ambos marcadores coinciden en el lugar, se puede abrir la puerta del robot.”

En la prueba del Robot de ADN, los investigadores lo cargaron con fragmentos de anticuerpos directamente a dos tipos diferentes de células cancerígenas, después lo programaron para abrirse cuando encontrara una de ellas. Tras su apertura, el robot liberó fragmentos a la célula con instrucciones de suicidarse.

“Finalmente hemos podido integrar detección y funciones de lógica computacional mediante complejas, pero predecibles, nanoestructuras destinadas a ser muy útiles”. El investigador Dr. George Church.

Los Robots son ideales para suministrar químicos dentro del cuerpo, es compatible con el sistema biológico y es naturalmente biodegradable. Además, debido  a que los robots pueden actuar solamente sobre ciertas células, es posible usar dosis menores de medicamentos, lo que limitaría el efecto tóxico y sería más efectivo.  Aún está en “Beta Test”, con puras cajas de Petri, pero sus promesas son importantes.

La fuente es aquí: http://www.forbes.com/sites/alexknapp/2012/02/17/scientists-target-cancer-with-dna-robots/

Los resultados del experimento son acá: http://www.sciencemag.org/content/335/6070/831.abstract

Supermateriales con origami de ADN; Superlentes y Nanobots!

En el Wyss Institute for Biologically Inspired Engineering de la Universidad de Harvard, el biofísico Shawn Douglas explica como las características del ADN; debido a que está formado por cuatro bases (Adenina, Timina, Guanina, y Citosina,), y que estas se unen en pares de tal manera que A se conecta a T y C a G, estas relaciones se pueden usar para crear materiales, lo único necesario es un “proyecto”.

El proyecto  incluye dos componentes principales; una larga cadena de ADN llamada andamio con unas 7000 bases, y una pequeña grapa que tiene entre 30 y 50 bases. Mientras las bases entre ambos componentes embonan, se puede plegar el andamio a la forma apropiada. Incluso se puede diseñar las grapas para tener enlaces químicos donde los investigadores pueden añadir otro material.

El inventor del origami con AND es Paul Rothemund en asociación con Catech hace seis años (2006), diseñando  formas bidimensionales como estrellas y caras sonrientesJ. Desde entonces el método se ha vuelto cada vez más popular en el campo de la bionanotecnología.

En un estudio publicado en Nature está semana (si, esta semana, la segunda del mes Marzo) científicos de Múnich usaron origami de ADN para crear dos tipos de espirales cilíndricas con pequeñas piezas de oro arregladas a lo largo de los extremos con una función en específico. El líder del equipo de Múnich que corre la investigación, Tim Leidl dice “En nuestro caso, la utilidad es que puede interactuar con la luz.” Por ejemplo, si las espirales están todas rotadas a la derecha en una solución, se absorbe luz de manera diferente a que si está a la izquierda. “De esta manera se prueba que usando auto-ensamble se pueden crear materiales con una función prediseñada” Anton Kuzyuk, un estudiante de post doctorado que trabajó en el estudio.

Fluidos que con las partículas de oro en cuestión.

All credit to: Kuzyk, Screiber, Hohmann

En sus estudios, los investigadores especulan que en un futuro el desarrollo de esta iea puede provocar el desarrollo de nuevos materiales con propiedades ópticas extrañas, como un índice de refracción negativo. Con estos metamateriales se pueden diseñar superlentes, o lentes perfectos, que permitirían ver objetos tan pequeños como virus.

Ahora lo de los nanobots: Hace una semana Douglas publicó un ensayó para Science que lo describe (y que será mi siguiente publicación). Estos nanobots fueron diseñados usando el origami de ADN para llevar fragmentos de anticuerpos y pueden identificar y destruir células cancerígenas.

Aunque a la investigación aún le falta mucho para poder ser probada en humanos, es una demostración de lo que el método descrito es capaz de construir, ya que como comenta Douglas “la evidencia de diversidad en la vida es una prueba del poderoso método de construcción que tiene el ADN.”

Fuente: http://www.popularmechanics.com/science/health/genetics/how-it-works-dna-origami-7383319

Telaraña da una idea sobre como encadenar nanotubos de carbono

Un estudio realizado por el MIT y publicado el 2 de febrero del 2012 en Nature. International Weekly Journal of Science (click aquí http://www.nature.com/nature/current_issue.html) analizó las características específicas de la tela de araña, donde se demostró que sus propiedades cambian y varían dependiendo del entorno. En el artículo “Spider Silk Is Strong Because It’s Smart” publicado el 1° de febrero del presente año en la página Wired (click aquí http://www.wired.com/wiredscience/2012/02/spider-web-strength/) el coautor del estudio Markus J. Buehler explica que debido a que la telaraña debe atrapar presas, soportar ataques e incluso vientos huracanados “La seda de araña tiene una manera particular de ser blanda y luego ser dura, lo cual es esencial para su funcionamiento correcto.” Usando modelos de computadora y experimentos de la araña de jardín Europea (Araneus diadematus) Buehler y su equipo encontraron las habilidades únicas de reacción a diferentes niveles de estrés. Por ejemplo; frente a un viento ligero la telaraña se hace suave, lo que hace que la red se estire pero mantenga su estructura. En cambio si una fuerza mayo es aplicada a una zona específica, la tela se hace rígida y se rompe. Haciendo que pequeñas porciones de la red se rompan no solo ayuda a mantener la integridad de la estructura, si no que hace la red más fuerte (permite cargar de 3 a 10% más peso). Esto muestra que la estructura es inteligente, y además aumenta la ventaja sobre otros materiales como el acero que se compromete en las mismas condiciones. Los conocimientos se pueden aplicar en varios retos: La habilidad para obtener pequeño daño sin comprometer la estructura puede ser usada para diseñar redes virtuales (Internet) donde un nodo local es sacrificado durante un ataque para evitar que el sistema caiga. Y, además, entendiendo cómo la proteína da a la estructura sus propiedades, podría ayudar a encadenar los nanotubos de carbono, lo que puede producir desde artículos de combate hasta ascensores espaciales. Serch out.

Field emission behavior of vertically aligned ZnO nanowire planar cathodes.

Field emission behavior of vertically aligned ZnO nanowire planar cathodes.

Planar surfaces covered with vertically aligned (VA) 

field emitters have proved to be efficient electron sources for 

micronanoelectronic applications. Initiated by the introduction of Spindt-type microtips, 

it was the input of VA-carbon

nanotubes (VA-CNTs) directly grown on a planar surface 

that has focused the attention to the possibility of using onedimensional nanostructures—i.e., nanotubes or nanowires—

as alternative routes for preparing planar cathodes.

A field emission (FE) study by scanning anode field emission microscopy was performed to evaluate the FE properties of vertically aligned zinc oxide (ZnO) nanowire arrays electrodeposited on a plane conductive surface.An effective surface barrier of about 1 eV was determined from the experimental "Fowler-Nordheim plot" and the presence of a Zn enriched surface was assumed in considering the possibility of important modifications of the crystallography and charge transfers at the surface of ZnO nanowires during the application of the strong electric field required for FE.

In conclusion the VA-ZnO nanowires present many advantages thatmake them a good candidate as a material for planar FE cathode. We can highlight two of them, a straightforward growthprocess by electrodeposition directly on the surface of a rigid or flexible large area substrate and a low turn-on voltage, in the range of 6 V/lm, for FE.

The original paper is in:

http://web.ebscohost.com/ehost/detail?vid=20&hid=104&sid=decf8496-8668-4b9a-93d7-2fcdb9eea757%40sessionmgr115&bdata=JnNpdGU9ZWhvc3QtbGl2ZQ%3d%3d#db=a9h&AN=59308933

Fabrication of Robust Crystal Balls from the Electrospray of Soft Polymer Spheres/Silica Dispersion

Self-assembly of colloidal particles into crystalline arrays is becoming one of themost intriguing fields because it is a relatively simple, cost-efficient strategy to fabricate novel materials with advanced functionality for some important potential applications such as photonic crystals biosensors, templates, and even paints, photonic papers, and cosmetics. Recently, fabrication of spherical assemblies (crystal balls or supraballs) of colloidal particles is of particular interest because these crystal balls possess photonic band gaps for normal incident light independent of position on the crystal surface, which is different from the anisotropies of the band gaps on crystal films and can be used as building units for more complex colloidal assemblies or even new types of photonic crystals, as pigments in paints, or as light diffusers for various light sources, including light bulbs and display screens.
In this article, they report a novel and facile approach to fabricate robust crystal balls directly through the self-assembly of “soft” polymer spheres by the aid of colloidal silica using the electrospraying technique. In this approach, “soft” colloidal polymer spheres are synthesized by emulsion polymerization and then blended with colloidal silica to obtain nanocomposite latex. When this dispersion is loaded into an injector and forced to flow through the nozzle under direct electric field, the detached droplets are collected by an oil solvent in which the colloidal polymer spheres and silica beads directly self-assemble into ordered crystal balls as water and solvent evaporate.
Different particle size, resulting in different colors
Compared to other techniques for fabrication of crystal balls, this approach is very simple, highly efficient, and can be used for mass of production of crystal balls. The obtained robust crystal balls have excellent mechanical properties towithstand external forces such as cutting, puckering, bending, and reversible deformation. Different color crystal balls can be tuned by the sizes of polymer spheres.The size and shape of crystal balls can be easily controlled by electric field strength solvent, container substrate, and surface charge density of polymer spheres. The excellent mechanical property and reversible deformation behavior of this crystal ball combined with its inherent isotropic optical property could open up a wider range of applications of crystal balls such as color pigments in reflection mode displays, e-papers, printing, and chemical and biological sensors.
Taken from:
Shen et al. Fabrication of Robust Crystal Balls from the Electrospray of Soft Polymer Spheres/Silica Dispersion. Langmuirpp. 6604-6609.

Metamaterials May Advance With New Femtosecond Laser Technique

Researchers in applied physics have cleared an important hurdle in the development of advanced materials, called metamaterials, that bend light in unusual ways. Working at a scale applicable to infrared light, the Harvard team has used extremely short and powerful laser pulses to create three-dimensional patterns of tiny silver dots within a material. Those suspended metal dots are essential for building futuristic devices like invisibility cloaks.

The new fabrication process, described in the journal Applied Physics Letters, advances nanoscale metal lithography into three dimensions -- and does it at a resolution high enough to be practical for metamaterials.
"If you want a bulk metamaterial for visible and infrared light, you need to embed particles of silver or gold inside a dielectric, and you need to do it in 3D, with high resolution," says lead author Kevin Vora, a graduate student at the Harvard School of Engineering and Applied Sciences (SEAS).
"This work demonstrates that we can create silver dots that are disconnected in x, y, and z," Vora says. "There's no other technique that feasibly allows you to do that. Being able to make patterns of nanostructures in 3D is a very big step towards the goal of making bulk metamaterials."
Vora works in the laboratory of Eric Mazur, Balkanski Professor of Physics and Applied Physics at SEAS. For decades, Mazur has been using a piece of equipment called a femtosecond laser to investigate how very tightly focused, powerful bursts of light can change the electrical, optical, and physical properties of a material.When a conventional laser shines on a transparent material, the light passes straight through, with slight refraction. The femtosecond laser is special because it emits a burst of photons as bright as the surface of the sun in a flash lasting only 50 quadrillionths (5 × 10-14) of a second. Instead of shining through the material, that energy gets trapped within it, exciting the electrons within the material and achieving a phenomenon known as nonlinear absorption.
Inside the pocket where that energy is trapped, a chemical reaction can take place, permanently altering the internal structure of the material. The process has previously been exploited for 2D and simple 3D metal nanofabrication.
Complete article in here
Kevin Vora, SeungYeon Kang, Shobha Shukla, Eric Mazur. Fabrication of disconnected three-dimensional silver nanostructures in a polymer matrix. Applied Physics Letters, 2012; 100 (6): 063120 DOI: 10.1063/1.3684277

Clay−Chitosan Nanobrick Walls: Completely Renewable Gas Barrier and Flame-Retardant Nanocoatings

Polysaccharides are naturally occurring polymers that are widely available in nature. Of the many types of polysaccharides, chitin is the second most abundant after cellulose. Chitin is extracted from the shells of crustaceans (e.g., lobsters and shrimp) and the exoskeletons of arthropods (e.g., insects). Despite its abundance, unmodified chitin’s usefulness is very limited, because of its poor solubility in most solvents. Chitosan, which is an amino polysaccharide obtained via the alkaline deacetylation of chitin is soluble in acidic aqueous solutions, because of the protonation of its amino groups at pH <6.2.In addition to its solubility, chitosan is biodegradable, biocompatible, and benign. These traits have led to the significant study of chitosan’s use in biomedical applications, such as drug delivery, wound-dressing materials, artificial skin, and blood anticoagulants.

In an effort to create fully renewable and multifunctional assemblies, thin films of chitosan and MMT clay were deposited on polyurethane (PU) foam and polylactic acid (PLA) film. P Thin films prepared via a layer-by-layer (LbL) assembly of renewable materials exhibit exceptional oxygen barrier and flame-retardant properties. Positively charged chitosan (CH), at two different pH levels (pH 3 and pH 6), was paired with anionic montmorillonite (MMT) clay nanoplatelets. Thin-film assemblies prepared with CH at high pH are thicker, because if the low polymer charge density. A 30- bilayer (CH pH 6-MMT) nanocoating (∼100 nm thick) reduces the oxygen permeability of a 0.5-mm-thick polylactic acid film by four orders of magnitude. This same coating system completely stops the melting of a flexible polyurethane foam, when exposed to direct flame from a butane torch, with just 10 bilayers (∼30 nm thick). Cone calorimetry confirms that this coated foam exhibited a reduced peak heatrelease rate, by as much as 52%, relative to the uncoated control. These environmentally benign nanocoatings could prove beneficial for new types of food packaging or a replacement for environmentally persistent antiflammable compounds.

The goal of this work was to develop a truly “green” film with flame-retardant and oxygen-barrier characteristics. Films assembled with high-pH or low-pH chitosan (CH) and clay (montmorillonite, MMT) showed linear growth as a function of the number of bilayers deposited. Higher chitosan pH resulted in much thicker assemblies with higher clay loading. An oxygen permeability of <0.03 × 10−16cm3cm/(cm2s Pa) was achieved with 30 bilayers (30 BL) of CH pH 6-MMT(< 100 nm thick). The combination of all of these features it is generally recognized as a safe material, it has high oxygen barriers, and the transparency exhibited by this film makes it an ideal candidate for food and other types of high-performance packaging.

Clay−Chitosan Nanobrick Walls: Completely Renewable Gas Barrier and Flame-Retardant Nanocoatings

Galina Laufer, Christopher Kirkland, Amanda A. Cain, and Jaime C. Grunlan*

Department of Mechanical Engineering, Texas A&M University, College Station, Texas 77843, United State

Find more information here

Controlling Novel Red-Light Emissions by Doping In2O3 Nano/Microstructures with Interstitial Nitrogen

Red-light has been used as phototherapy in the medical field because of its long wavelength (620-750 nm) that can easily penetrate through the body of patients. Red-light can also be used for many commercial, industrial, and medical applications, as well as a necessary device source of red laser eyesight for military weapons. Thus, photoluminescence (PL) and electrolu- minescence materials and electronic devices, with the capability to emit red-light under proper conditions, have been a long- time scientific pursuit after the first successful red-light light- emitting-diode (LED) was obtained in the early 1960s. Nano/ microstructured semiconducting materials are considered as the primary sources for enhancing red-light emitting efficiency and enhancing the precision of laser-guided weapons. In addition, red-light emitting nano/microstructured materials may be used as red fluorescence powder, acting as one of the basic fluorescence additives for preparing white LED fluorescent lamps. Indium oxide (In₂O₃), a promising wide bandgap semiconductor with a bandgap of 3.6 eV, shows technologically important applications in optoelectronic devices such as lasers, fluorescent lamps, orientation lamps, display devices, and infrared reflectors. For example, it has been reported that nanosized In₂O₃materials exhibit tunability in the wavelength ranges from ultraviolet (UV) to visible blue-green as well as yellow emission for optoelectronic devices. However, red- light emission was rarely reported from these In₂O₃ nanostructures. Wenyan Yin and his team report that interstitially N-doped In₂O₃ nano/ microstructures including nanorods, nanoellipses, microspheres, and microbricks, which have recently been developed in their group by annealing the corresponding In(OH)₃ precursors, show a unique and wide range red-light emission under 350 nm wavelength excitation, in addition to blue-light emissions. They first made the arrays of In₂O₃ and then they doped it with N, filling interstitial vacancies in the crystal cells.

Crystal Cell

The full article can be found at the. Phys. Chem. 114, 13234-1324. Wenyan Yin et al. Controlling Novel Red-Light Emissions by Doping In2O3 Nano/Microstructures with Interstitial Nitrogen