First Direct Images of Carbon Nanotubes Entering Cells

Nov 15, 2007 By Laura Mgrdichian feature
First Direct Images of Carbon Nanotubes Entering Cells
This transmission electron microscope image shows carbon nanotubes (dark areas) within a cell nucleus.

For the first time, scientists have directly imaged carbon nanotubes entering and migrating within human cells, determining as a result that whether the nanotubes cause cell death depends on the dose and exposure time. The work, published in the October 28 online edition of Nature Nanotechnology, may lead to better ways of determining carbon nanotubes' toxicity to humans.

This study is the first to show definitively that carbon nanotubes have the ability to cross into the cytoplasm and nucleus of a cell.

Many studies have explored the toxicity of carbon nanotubes, some concluding that the nanotubes are acutely toxic and some not. But the uptake of carbon nanotubes by cells has never before been directly observed, casting doubt on the accuracy of those studies.

“Contradictory data on the toxic effects of single-walled carbon nanotubes highlight the need for alternative ways to study their uptake and cytotoxic effects in cells,” lead scientist Alexandra Porter, of the University of Cambridge in the UK, said to PhysOrg.com. “But the direct observation of cellular uptake of single-walled carbon nanotubes has been hindered by difficulties in discriminating carbon-based nanotubes from carbon-rich cell structures.”

Porter and her colleagues from the University of Cambridge and Daresbury Laboratory, also in the UK, used two types of microscopy to image single-walled carbon nanotubes as they entered macrophages, which are cells of the human immune system. They “watched” the nanotubes enter the cytoplasm, certain organelles, and the nuclei.

The group chose macrophages because they are the first line of defense against foreign materials in many tissues in the body, including lung tissue. Nanoparticles that are inhaled, such as carbon nanotubes in powder form, should be ingested by macrophages, which may stop the nanotubes from getting further into the body’s system, such as the blood and lymph systems (lymph is a clear fluid containing white blood cells and tissue waste that is part of the body's defense against infection).

The cells were analyzed both stained and unstained and the results compared to two common viability tests, or “assays.” These assays gauge the health of the cells using different markers, and thus can have different results. On the other hand, the imaging techniques the scientists used determine cell death by allowing clearly defined structural changes to be identified, and could therefore become an essential complement to carbon-nanotube toxicity assays.

The cells analyzed were treated with nanotube solutions over time periods of two and four days at concentrations between zero (no nanotubes) and 10 micrograms (millionths of a gram) per milliliter.

The images revealed that even cells subjected to the highest nanotube concentrations were still relatively healthy after two days; there were no major differences between the control cells, which were not treated, and the nanotube-treated cells. But after four days, even the lower concentrations led to a significant decrease in the cells' viability.

After two days, the nanotubes had entered the cells' lysosomes, organelles in the cytoplasm that cause the breakdown of metabolic substances and foreign particles within the cell. After four days, the nanotubes had fused together; some had entered the cytoplasm and crossed into the nucleus.

“Uptake to these sites implies that the nanotubes may interact with intracellular proteins, organelles, and DNA, which would greatly enhance their toxic potential,” said Porter.

The two imaging techniques used are transmission electron microscopy (TEM) and confocal microscopy. In TEM, a beam of electrons passes through a thin specimen, forming an image that is recreated on a fluorescent screen, photographic film, or detected by a camera. Confocal microscopy involves the use of light to increase the contrast of an image by eliminating all light that is not in the focal plane of the image, resulting in a much sharper image.

Citation: Alexandra E. Porter, Mhairi Gass, Karin Muller, Jeremy N. Skepper, Paul A. Midgley and Mark Well Nature Nanotechnology advance online publication, 28 October 2007 (doi:10.1038/nnano2007.347)

Copyright 2007 PhysOrg.com.
All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com.

Explore further: Nano-forests to reveal secrets of cells

add to favorites email to friend print save as pdf

Related Stories

Inexpensive flexible fiber perovskite solar cells

Aug 04, 2014

(Phys.org) —Textile solar cells are an ideal power source for small electronic devices incorporated into clothing. In the journal Angewandte Chemie, Chinese scientists have now introduced novel solar cells ...

Recommended for you

Nano-forests to reveal secrets of cells

8 hours ago

Vertical nanowires could be used for detailed studies of what happens on the surface of cells. The findings are important for pharmaceuticals research, among other applications. A group of researchers from ...

Intricate algae produce low-cost biosensors

Sep 01, 2014

(Phys.org) —Oregon State University researchers are combining diatoms, a type of single-celled photosynthetic algae, with nanoparticles to create a sensor capable of detecting miniscule amounts of protein or other biomarkers.

Introducing the multi-tasking nanoparticle

Aug 26, 2014

Kit Lam and colleagues from UC Davis and other institutions have created dynamic nanoparticles (NPs) that could provide an arsenal of applications to diagnose and treat cancer. Built on an easy-to-make polymer, these particles ...

User comments : 14

Adjust slider to filter visible comments by rank

Display comments: newest first

Nikola
not rated yet Nov 15, 2007
This just made my ever-growing list of "Things to Worry About"
googleplex
3.6 / 5 (5) Nov 15, 2007
Hmm this sounds very ominous and I feel disapointed that it might be a show stopper for nano tech.
4 days survival does not sound long when some human cells are supposed to last us for years. The last thing you want is something wandering around your DNA that can slip in between the base pairs and cause replication mistakes i.e. mutations.
What you have is a finely tuned machine (the cell) having millions of wrenches thrown in it. How could they not interfere? Especially when you consider that the wrenches are alien to our organism. The cell has not (yet) evolved to cope with carbon nano tubes. However it has had millions of years to cope with other molecules like proteins, enzymes, hormones...
albert
5 / 5 (1) Nov 16, 2007
Hmm this sounds very ominous and I feel disapointed that it might be a show stopper for nano tech.
4 days survival does not sound long when some human cells are supposed to last us for years. The last thing you want is something wandering around your DNA that can slip in between the base pairs and cause replication mistakes i.e. mutations.
What you have is a finely tuned machine (the cell) having millions of wrenches thrown in it. How could they not interfere? Especially when you consider that the wrenches are alien to our organism. The cell has not (yet) evolved to cope with carbon nano tubes. However it has had millions of years to cope with other molecules like proteins, enzymes, hormones...
albert
2.3 / 5 (3) Nov 16, 2007
Dear Sirs,
I am sorry for somehow "copying" a comment under my name "Albert". . .the comment is by Fredrick and I don't know how to get in touch with him. I am very concerned about this article and its implication. . .already there are thousands who have illnesses associated with nanotech. Morgellon's disease is growing and particles are being found in the human body that are not natural, that cannot be burned at 1700 degrees. Anyone wishing to start a dialogue may reach me at alsoulsound@yahoo.com
rmuldavin
5 / 5 (2) Nov 16, 2007
It should be initially assumed serious damage can occur for use of nano tubes as above do show invasion of inter cell organelles. The at a distance drives for monetary returns show sufficent damages to warrant, at least equal division of research into products and health.
All with open discussion within initial groups and thereon into wider open discussion.
A small thing, but with large consequences.
miuws
2 / 5 (2) Nov 18, 2007
Morgelleons, Chemtrails, and Nanotubes, is anyone
researching a possible conection here?
I'm a novice in the world of science, but have a great interest in the above subjects. would be interested in what others have to say on this question.cjw
LearmSceince
3.3 / 5 (3) Nov 19, 2007
Morgelleons [sic], Chemtrails, and Nanotubes, is anyone
researching a possible conection [sic] here?
I'm a novice in the world of science, but have a great interest in the above subjects. would be interested in what others have to say on this question.cjw


What kind of "connection"? That is a random assortment of topics. Nanotubes are interesting structures made of carbon. They are no different then anything else that size, such as protein and plastic molecule chains, in that they may have some affect on the body.
Chemtrails are a delusion of a type of paranoia. Those people think that white lines caused by water condensation are actually part of a magor conspiracy.
Morgellon's disease is being looked at by the medical community. It's probably just a new name for an existing condition that was described 75 years ago.
saucerfreak2012
1 / 5 (2) Nov 21, 2007
@LearmScience

I suggest you "Learm" about a topic before injecting ridicule and mockery into a serious topic.
You can start here http://www.chemtr....shtmlan

btw, it's maJor not maGor :)
eschaton
5 / 5 (2) Nov 21, 2007
this was done on macrophages which vacuum up debris inside the body. I dont think it matters of too much if the nano tubes clog up some macrophages. What they need to do is some animal studies and look and see if it gets into body tissue such as lung, lymph nodes, nerve cells... so on and so forth. I think its likely! I saw a study where most of these nano particles are already present in diesel exhaust and that those diesel particles are potent carcinogens.
LearmSceince
5 / 5 (3) Nov 21, 2007
saucerfreak: Your link is bad. Try this one. And I have learned about the subject, which is why I don't simply repeat nonsense. Learning means looking at evidence and data and their credibility and repeatability; NOT simply holding a position despite any evidence. My previous reply would only be seen as ridicule by someone who is so afflicted.
See also information about contrails. Note in particular how "chemtrail" dogma disagrees with this for particulars such as formation and dissipation rate, and other things that can be measured and observed by anyone. To oversimplify, anyone with a little physics can figure out that statements such as distinguishing chemtrails from proper contrails based on dissipation rate is simply wrong.
NeilFarbstein
3 / 5 (2) Dec 18, 2007
It's obvious nanotubes can destroy macrophages and there seems to be no way to eliminate them from the body. They might also kill macrophages in atheroscerotic plaques casuing heart attacks and strokes if people are exposed to nanotubes chronically.

Hmm this sounds very ominous and I feel disapointed that it might be a show stopper for nano tech.
4 days survival does not sound long when some human cells are supposed to last us for years. The last thing you want is something wandering around your DNA that can slip in between the base pairs and cause replication mistakes i.e. mutations.
What you have is a finely tuned machine (the cell) having millions of wrenches thrown in it. How could they not interfere? Especially when you consider that the wrenches are alien to our organism. The cell has not (yet) evolved to cope with carbon nano tubes. However it has had millions of years to cope with other molecules like proteins, enzymes, hormones...
superhuman
5 / 5 (1) Mar 08, 2008
If they can enter nucleus they pose high risk to all cells, especially since cells don't have proper enzymatic tools to disassemble them.
It is quite probable that nanotubes will accumulate in our organisms cause there are no ways in which cells can handle them and transfer them out of the body.

One way to help prevent nanotubes from entering cells would be to somehow make their surface charged, it should prevent them from diffusing through cellular membranes. In their present form I don't see how any lipid bilayer can stop them.

This looks like a serious problem for any future use of carbon nanotubes.
billydude
not rated yet Oct 02, 2008
One way to look at this problem is to evaluate how many natural nano-size materials that are already present in our lives and how do our body cope with them now! I suspect that there is already a mechanism inside our body for dealing with it. If not, we may evolve one as well.
googleplex
not rated yet Oct 06, 2008
The first barrier in a cell is the phospholipid bilayer. Can these particles pass through?
I would add that evidence is growing of a new nano-class of pathogens e.g. CJD (mad cow). These are molecular bugs called prions. Much smaller than viruses. The only way to sterilize surgical instruments is using a plasma autoclave which is not used yet.
There is a pattern here. First we discover bacteria, then viruses and now prions. Each time is a jump in scale.
Each time we go to the dentist/surgeon we run the risk of catching a prion type pathogen (e.g. CJD or alzheimers). Current sterilization practice is woefully inadequate with these discoveries. Of course you can always ask them to use new surgical tools.