08 September 2010

Graphene Nanoparticles against cancer

A method of cancer treatment using graphene and laser is proposedVera Bashmakova, Elements
Source: Kai Yanget al., Graphene in Mice: Ultrahigh In Vivo Tumor Uptake and Efficient Photothermal Therapy.
// Nano Letters.

Graphene is a rising star in the sky of nanotechnology. On its basis, they are going to make transistors of a new generation, sensors for determining a single molecule of a substance and electrodes for supercapacitors. And now it turns out that a great medical future awaits him. It turned out that, when injected into the circulatory system of mice with cancer, graphene selectively accumulates in tumors. If you then use the high absorption capacity of graphene at near infrared frequencies and irradiate the tumor with a laser, it will literally burn up, and the mouse will recover. Moreover, what is especially inspiring, the researchers did not find any side effects of such treatment in the experimental mice.

The idea of embedding some kind of nanotube into a tumor, and then using it to burn the tumor, has been visiting the heads of scientists for a long time. However, none of the nanomaterials tested was perfect. For example, carbon nanotubes accumulated not only in a cancerous tumor, but also in some other organs of the mouse, and when the tumor began to burn the laser, not only it burned.

Graphene can be called a relative of a carbon nanotube: it is the same layer of carbon atoms, only not rolled into a cylinder, but flat. This similarity suggested that it should also accumulate well in cancerous tumors. And when scientists tried to see how graphene would behave in a mouse body with cancer, the results were simply brilliant: for some reason (maybe because of its flat structure) graphene accumulates much better by the tumor, and practically does not linger in other tissues.

The experiments used graphene coated with a biocompatible polyethylene glycol shell ("naked" graphene is unstable in a living organism). The experiment consisted of several stages.

First of all, the researchers just had to figure out what happens to graphene after it is inside the body. To do this, graphene was marked with Cy7 fluorescent paint, injected into the vein of experimental mice and its content in the blood was measured every few hours. It turned out that after six hours his level drops to almost zero. This was very, very gratifying.

Graphene level drop in the blood of experimental mice depending on time.
%ID/g is the percentage of the administered dose per gram of weight.
Graph from the discussed article in Nano Letters

After that, the scientists injected graphene into the blood of mice with cancerous tumors and began to look at the dynamics of its distribution in the mouse body. It turned out that after 24 hours graphene accumulates in the area of the tumor and is much less represented in the rest of the body. It is worth noting that the level of graphene in the kidneys remained relatively high; the researchers suggested that some graphene particles are so small that they can leave the body with urine.

Distribution of graphene throughout the mouse body at different time intervals after its introduction.
4T1, KV and U87MG are different types of cancerous tumors.
Image from the discussed article in Nano Letters

Now scientists have decided to actually treat cancer. 33 mice received a cancerous tumor on the right shoulder; after that, 17 of them were injected with graphene, and the rest remained for control. A day after the injection, the tumors of ten injected and ten non-injected mice were irradiated with a laser with a wavelength of 808 nm, at which graphene absorbs light especially well. Thus, the scientists worked with one experimental ("graphene + irradiation") group and three control groups ("graphene only", "irradiation only" and "neither one nor the other").

The tumors of the experimental mice literally burned up – the temperature on the surface of the body at the irradiation site jumped by 50 ° (in control mice – by only 2 °). The next day, the cancer in these mice disappeared, leaving behind only a characteristic black scar, which noticeably decreased a week after irradiation. During the 40 days that the study lasted, no signs of tumor return were found in these mice. At the same time, all three control groups of mice had cancer, and their average life expectancy after the start of the experiment was 16 days.

Typical photos of mice from four groups participating in the experiment.
NGS-PEG – graphene coated with polyethylene glycol
(nanographene sheets with polyethylene glycol).
It can be seen that in a mouse injected with graphene and irradiated with a laser, the tumor is destroyed.
Image from the discussed article in Nano Letters

The results were brilliant, but they wouldn't have made any sense if the method had some harmful side effects. However, everything was perfect here: during the 40 days of the study, not a single experimental mouse died, the animals showed no symptoms of illness or weight loss; after the end of the experiment, the scientists examined sections of the internal organs of the experimental mice and found no signs of damage.

Comparison of sections of internal organs of "graphene" and "non-graphene" mice.
Healthy untreated – healthy uninjected mice,
NGS-PEG treated – mice that received graphene injection.
Kidney – kidneys, liver – liver, spleen – spleen, heart – heart, intestine – intestines, lung – lungs.
Image from the discussed article in Nano Letters

Of course, it's too early to say that a magic wand has appeared that will cure all patients with one wave. It's just a very successful pilot study. The groups on which the study was conducted were too small, and the experiment time was too short, and it is quite possible that some cunning side effect escaped the attention of scientists. In addition, the tumors in the mice were not "native", grown in their own body, but transplanted, that is, transplanted. It is quite possible that graphene accumulates better in them for some reason than in the "native" ones. There are also several unclear places in the study. For example, when scientists claimed that the recovered mice did not lose weight, they compared them with control groups that had cancer and could not help but experience health problems. In addition, mice themselves are much more likely to get cancer and recover much more easily than humans, and further experiments on other animal species can lower us from heaven to earth.

Nevertheless, this study is a great start, and let's hope that the continuation will not be worse.

Portal "Eternal youth" http://vechnayamolodost.ru08.09.2010

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