Slashdot Mirror
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."
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.
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.
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.