Cell Growth: CNTs made as a substrate promote cellular growth

Reports of toxicity of CNTs are usually presented when the mode of delivery is free floating in media, not for a substrate with CNTs embedded, whereas CNTs embedded into a substrate or made as a substrate promote cellular growth. Depending on the mode of exposure and/or material presentation, CNTs may lead to toxicity or promoted tissue growth (although significantly more research is required). Furthermore, it is important to emphasize that not all CNTs are the same. Some impurities may be left over from unreacted catalysis known to be toxic to cells, while others have fully reacted catalysts presenting relatively pure CNTs to cells. Such differences in CNTs can clearly have profound influences on CNT toxicity.

David A. Stout  and Thomas J. Webster, Materials Today, JULY-AUGUST 2012 | VOLUME 15 | NUMBER 7-8| pp 315

A microfluidic system is introduced for simultaneously measuring single-cell mass and cell cycle progression over multiple generations. This system was used to obtain over 1,000 h of growth data from mouse lymphoblast and pro–B-cell lymphoid cell lines.

Scott R Manalis, (Koch and MIT), Direct observation of mammalian cell growth and size regulation, Nature, Vol 9, No 9, Sept 12

In a comprehensive single-cell study to examine the inter-relationship of cell growth and the cell cycle – single yeast cells were studied microscopically using a fluorescent reporter protein as a proxy for cell mass Di Talia, S., Skotheim, J.M., Bean, J.M., Siggia, E.D. & Cross, F.R. Nature 448, 947–951 (2007).

CyberScanning Electron Microscopy

Access SEM over the Web:

Oxford University’s Materials Dept. has developed an interface that gives control of a dedicated scanning electron microscope (SEM) to schools over the Web. The full-scale dedicated SEM is installed in Oxford, and is currently being road-tested over the Internet to ensure that it is both easy to use and robust. Modules of supporting documentation (including detailed lesson plans) are available for download.

The remote operator can change the microscope magnification, move around the sample, focus and capture images directly onto his/her computer at a range of resolutions. The remote operator can choose between a set of samples, selected as most appropriate for student learning in the 14-18 age group. At present, most samples are focused on the biology curriculum and include leaves, rat skin, E. coli, sperm, bacteria, salmonella, rat kidney, radiolarians, trachea, lung and pollen, but plans are in place to broaden into the physics and technology curricula.

LOG IN TO SYSTEM HERE:

http://websemserver.materials.ox.ac.uk/htdocs/index.php

 

More resources:

http://www.denniskunkel.com/PublicHtml/Edu-JavaScriptSEM.asp

http://www.mos.org/sln/sem/tour15.html

http://www.unl.edu/CMRAcfem/em.htm

Light sheet based microscopy LSM

 

Light-sheet based microscopy (LSM), also known as single plane illumination microscopy (SPIM), is a state-of-the-art microscope imaging method in which a biological sample is illuminated with a thin sheet of light—provided by a laser beam narrowed to just a few microns, or millionths of a meter, across—coming from the side rather than from above or below as with traditional light sources. Fluorescence bouncing off the illuminated sample radiates upward through a lens, gets focused and is captured by a digital camera.

Because the light sheet illuminates the part of the sample directly in the same plane, only a single section of the target is imaged at a time. Raising and lowering the illumination plane, as well as rotating the sample, rapidly produces a series of two-dimensional sectional views known as “slices” that can yield a 3-D map of a whole organism or any of its organs/systems when the individual 2-D visual pieces are brought together.

One region that scientists have tried to survey in mice with LSM is the neural pathway, the billion-fold network of neurons that underlie the functioning of the brain. While the LSM method yields high-resolution views of tissue excised from mouse brains and fixed in position, whole brain samples scatter the emitted light and create background fluorescence that reduces contrast and blurs the perceived image. Obviously, this aberration makes it impossible to resolve and reconstruct the entire neuronal network with a high contrast.

To correct the problem, scientists combined the advantages of light sheet illumination with confocal microscopy, an imaging method that uses a filter to remove photons that stray from the single plane of the thin sheet.

They found that the combined system, which they call confocal light sheet microscopy or CLSM, filtered the scattered photons that were emitted and recovered the normally lost image contrast in real time without the need for multiple acquisitions or any post-processing of the acquired data. http://www.nanowerk.com

HRTEM images of individual atoms in graphene with unprecedented resolution

Low-voltage HRTEM imaging of dislocation dynamics in graphene is presented, using both spherical aberration correction and monochromation of the electron beam using a double filter. Graphene samples were prepared using chemical vapor deposition (CVD) on copper foils and were transferred onto silicon nitride TEM grids with 2-μm holes (see the supplementary materials for details).

 

 

 

 

 

 

Imaging edge dislocations. (A) HRTEM image showing two opposing (1,0) edge glide dislocations in graphene. (B) Structural model representing the dislocation pair (blue and green) in (A). (C) HRTEM image simulations using the atomic model in (B) as a supercell. False color is used for the images to aid visual inspection.

Source: Oxford University Materials Dept., Read the full text here:

http://www.sciencemag.org/content/337/6091/209.full

Two Photon Excitation Microscopy

Two-photon excitation microscopy is a fluorescence imaging technique that allows imaging of living tissue up to a very high depth, that is up to about one millimeter. Being a special variant of the multiphoton fluorescence microscope, it uses red-shifted excitation light which can also excite fluorescent dyes. However for each excitation, two photons of the infrared light are absorbed. Using infrared light minimizes scattering in the tissue. Due to the multiphoton absorption the background signal is strongly suppressed. Both effects lead to an increased penetration depth for these microscopes. However, the resolution remains diffraction-limited. Two-photon excitation can be a superior alternative to confocal microscopy due to its deeper tissue penetration, efficient light detection and reduced phototoxicity.

Source: http://en.wikipedia.org/wiki/Two-photon_excitation_microscopy

 

Dose response relationships are significant in Nanotoxicology

There are opportunities for computational scientists to work with toxicologists to design new assays.

Since animal testing is reduced, computational methods are becoming increasingly important for prioritizing safety studies.

Traditional in vitro assays may misrepresent the response. Studying the influence of the various properties of nanomaterials, the dose, the exposure route and time, and identifying the right model systems is expensive and time consuming. High-throughput and computational approaches are on the horizon to rapidly screen and prioritize nanomaterials for toxicological tests and to develop causal relationships between material properties and biological behaviours

Nature Nanotechnology:

http://www.nature.com/nnano/focus/nanotoxicology/index.html

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