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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."
Perhaps a biologist can answer a question I've had about this, which is also related I suppose to Chemotherapy.
What is the difference between a cancer cell and a "normal" cell? Why would radiation therapy tend to kill cancer cells faster than normal cells? The article mentions that they are concerned that normal cells might be affected, but they don't explain why it would favor cancer cells in the first place.
Sometimes it's best to just let stupid people be stupid.
I've been wondering this for some time. Cancer cells are cells which multiply indefinatly, as opposed to normal cells, which only multiply for a specified amoutn of time, and then die off (with the exception of stem cells). Correct? Ok. Well' if I am right so far, can someone tell me why more research isn't going into controlling cancer, rather than destroying it? Like, I would think, if you could start and stop the cancer effect at will, you could live forever. Am I totally off base?
Actually, one of the greatest benefits of radioimmunotherapy compared to conventional radiation therapy is that it's much better at treating metastatic cancers. Since the radiation is attached to antibodies, it will circulate through the blood and attach to cancerous cells wherever they happen to be. That makes it a great technique for treating cancer that's spread beyond its initial tumor. A slight modification to the technique can also be used for diagnosis; they use a different isotope, one that emits gama-rays rather than alphas, and then use a gama-ray sensitive camera to image where the isotopes wind up. That lets them find out where the cancer has spread.
There's no point in questioning authority if you aren't going to listen to the answers.
Alpha emitters are great for this kind of work, because alpha particles have a high interaction cross section once they're inside the body. That concentrates their damage in a small space. (You can handle blocks of alpha-decay material without hazard, because the alpha particles plough into your epidermis and stop there, wreaking terrible damage on ... tissue that's already dead.)
I bopped on over to one of the online charts of the nuclides to check out the decay chain of Ac-225. Indeed, the next two daughters are alpha-emitters, but the first one, Fr-221, has a 5-minute half-life. That ought to give it plenty of time to get ducted around into your bloodstream and into the rest of your body before emitting the next two alphas and a couple of beta particles, eventually transmuting to stable Bismuth.
So the developers aren't being quite candid when they say that the daugter alpha particles could inflict additional damage on the tumor. Sure, they could -- but (with the antibody bonds long since broken by the recoil from the initial decay) that atom could end up anywhere in your body before decaying again.
This stuff is interesting -- I used to make radioactive saline at the Reed Reactor Facility for medical uses, so I poked around the chart of the nuclides to see how one would make Ac-225. Ideally, you want to start with a nice, stable (or at least long-lived) element, kick a neutron into it (by lowering the ore into a nuclear reactor), and let it turn into what you want via a series of rapid decays. (That's one way to make the Americium 241 in smoke detectors; I'll leave the source element as an exercise for the reader). But Ac-225 doesn't seem to have any such nice precursor decay paths with short half-lives. The half-life is short enough that you wouldn't want to get it from spent fuel (too `hot' until after the Ac-225 is gone!), so I'm not entirely sure how you'd make it.