Combining Nanotech and Radiology

Twilight1 writes "According to this article at CNN, researchers are testing a microscopic "smart bomb" to target, attack, and kill cancer cells. It's quite fascinating that they are using radioactive by-products from the production of nuclear power and weapons as the effective payload."

When I was a kid

[seann]

I saw this last night on @Discovery.ca, and it reminded me when I saw this on some TV show, this must of been my grade 6 (7 years ago).

I'm glad to see they finally have this in practical use.

Re:Normal cells

[Edgy Loner]

Divison.

Radiation, chemotherapy and the like are more likely to kill cells during division. Cancer cells divide all the time, hence are more sensitive to these agents. Most normal cells don't divide as much and aren't as senstive. Exceptions would be hthe cells that line the gi tract and form hair follicles. Which is why rad/chemotherapy tends to make people losse their hair.

The Crack Science Reporters at CNN

[EccentricAnomaly]

They are held together in the same way that magnets can stick together -- the isotope has a positive charge and the molecular cage has a negative charge.

Magnets do not stick together because one has a positive charge and the other has a negative charge. I learned this in third grade science.

Re:Normal cells

[yet another coward]

Cancer cells multiply abnormally fast, causing tumors. To accomplish this rapid proliferation, they replicate DNA more than normal cells. Ionizing radiation and chemotherapy often (always?) target DNA. By damaging DNA or causing manufacture of defective DNA, they preferentially affect cells that are multiplying rapidly. Many of the side effects are due to destruction of tissues with high rates of multiplication such as bone marrow and gut.

Re:chemotherapy does more than DNA

[davebo]

Just as an aside:

Chemotherapeutics (at least, some anthracyclines) not only muck around with DNA, but can lead to free radical generation & can damage cellular membrane components.

They're nasty, nasty molecules.

Reply from a cancer researcher..

[Chico Science]

I work at the National Cancer Institute and figured I'd give my personal scientific view (not official, since I'd get flayed for doing that).

While the research *is* interesting there are a lot of caveats. The article specified that this technique has been successful in treating a broad range of cancers. In culture. This means there's cells in a flask with medium and they add the agent to the medium. This means the cancers are definitely coming in contact. In a human system, this may not be the case. An intravenous injection may not service tumors embedded in tissues. Especially brain tumors because of the blood-brain barrier.

Another caveat. Nearly every system of targetted therapeutics involving antibodies has failed in humans, despite any remarkable results in mice. Several other wildly successful therapeutics in mice (angiogenesis inhibitors for example) are only modestly successful in humans.

Models, be they mouse or cell culture, do not carry over terrifically well to 'in the wild' cancers in humans. Entirely possible that these treatments will have some benefit for certain cases. On the whole, this isn't the "smart bomb" or "cure for cancer" the media portrays. Unfortunately, the AP doesn't report the caveats. Also, as of yesterday, I wasn't able to find any reference to this study in medical literature. I suspect that the moment the journal it was submitted to accepted the paper, a publicist was on the phone with the press. Accordingly, the media story is in the hands of the public before the peer reviewed article is.

Just another case of wait and see. I hope for the best, but don't expect it (sorry guys).

Ciao, C.Sc.

Boron/Neutron vs. Actinium

[chrisserwin]

It seems like a lot of the harmful side effects come from using actinium-225, which self-decays, not necessarily waiting until it has accumulated in it's targeted host. I wonder if they could use boron instead, which is fairly inert, and a beam of neutrons to accomplish the same task.

Back in my college co-op days, I worked at the Idaho National Engineering Laboratory in Reactor Design. Down the hall they were doing brain tumor studies on rats treated with a technique called BNCT: Boron Neutron Capture Therapy. The theory was to inject a water soluble boron compound into the body. Water soluble molecules do not pass well through the "blood-brain barrier", therefore, will not easily pass into healthy nerve cells. They do, however, accumulate in cancer tissues. Boron is nice because it is fairly inert until it interacts with neutrons and breaks down into alpha particles and non-threatening elements. So the theory was that the Boron would accumulate in the tumors and they could then bombard the tumor with neutrons, producing an explosion of alpha radiation... no more tumor. I didn't work on this project, and I'm not sure what became of it.... I think this technique may be used in other countries.

I think the nice thing about the current technique is the ability to target specific proteins. I wonder if a boron/neutron might have an additional advantage - unlike actinium which would decay over time (like the oven on "warm", the boron approach would be more immediate. Think "broil".

Re:A quick look at the Ac-225 decay chain...

[mmontour]

so I poked around the chart of the nuclides to see how one would make Ac-225[...]But Ac-225 doesn't seem to have any such nice precursor decay paths with short half-lives.

I did a bit of web searching (with my CRC "Table of the Isotopes" handy), and it looks like the key is Uranium-233.

U-233 can be formed in a breeder reactor from Th-232, by: Th-232 + n -> Th-233 -> Pa-233 + e- -> U-233 + e-

Once you have the U-233, U-233 -> Th-229 + alpha -> Ra-225 + alpha -> Ac-225 + e-

This page at ORNL [ornl.gov] indicates they have a stockpile of 400kg of Uranium-233, and are "the only significant source of bismuth-213 [3 decays down from Ac-225, also useful for cancer treatment] in the western hemisphere".

Re:Biology Question

[raffymd]

I'm rephrasing your question as "Can cancer be beneficial by providing immortal properties to an organism?" The answer is no because transformed cells (cells that have been deemed cancerous due to their uncontrolled replicative potential) lose their "differentiated" ability. That is, they stop functioning like they were supposed to. For example, a tumor in the liver (which decided to stop growing) is not beneficial to the liver because it doesn't do what liver cells are supposed to do (like synthesizing digestive and metabolic enzymes, etc.) If anything, it steals resources like nutrients away from functioning liver cells nearby. This tumor may not be lethal but it certainly isn't helpful.