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Cancer Drugs on a Raft Made of Algae

Researchers engineer tiny organisms to deliver cancer drugs to tumors without the usual nasty side effects—and at much less cost than conventional methods.
(Photo: Andrea Pokrzywinski/Flickr)

(Photo: Andrea Pokrzywinski/Flickr)

If you're like me, algae can inspire a surprisingly wide range of reactions and ideas. Sure, to some people, it's just icky pond scum; to others, however, it's the food of the future. At least one guy has proposed implanting photosynthetic algae under our skin so that we could, in his words "eat the sun." Now, researchers report they've developed a more immediately practical use, at least for one particular kind of algae: a tiny raft of sorts, to deliver cancer drugs straight to a tumor's door.

Well, not straight to a tumor's door—more to the point, only to a tumor's door. One of the biggest problems with cancer chemotherapy is that the drugs involved don't just kill rogue cancer cells; they target any rapidly dividing cells, which is why chemo patients often lose their hair. One solution is silica nanoparticles, which have recently emerged as a promising way to more narrowly target cancer cells. Roughly, the idea is to design an object perhaps a millionth the size of a grain of sand that attaches only to particular kinds of cancer cells, therefore delivering the drugs only to those cells. The upside is fewer side effects. The downside is that nanoparticles are hard to design and expensive to produce at the scales required for commercial pharmaceuticals.

The idea is to design an object perhaps a millionth the size of a grain of sand that attaches only to particular kinds of cancer cells.

But what if there was something easily produced that could serve the same purpose? There's an obvious candidate, Bahman Delalat, Nicolas Voelcker, and their colleagues point out in Nature Communications: diatoms, a type of algae that just so happens to encase itself in silica—the same stuff used in drug-delivering nanoparticle designs. In principle, researchers could genetically engineer diatoms so that their silica walls, or biosilica, could attach to both a cancer drug and immune system antibodies. Those antibodies already attach to cancer cells, tagging them so that white blood cells can identify and destroy them. Now, the thinking goes, cancer drugs can hitch a ride too.

While the researchers aren't the first to propose the diatom idea, they are among the first to test the idea on real cancer cells. The team first genetically engineered the diatom Thalassiosira pseudonana so that it would attach to the immune system's general-purpose antibodies. Next, they loaded up Thalassiosira pseudonana's biosilica exterior with Camptothecin, a drug that's shown promise in fighting cancer but that's also tough to deliver to cancerous tissue (and comes with some nasty side effects).

Finally, the researchers gave their special blend to mice with cancerous tumors that had been growing for 12 days—and it worked. After five days, tumor sizes went down by around half. Meanwhile, the engineered biosilica didn't show in most of the mice's organs, the exceptions being the liver and kidney, meaning that, for the most part, the team's design kept cancer-free tissues safe. This finding, the team writes, "paves the way for a novel drug delivery system using a biotechnologically tailored" material—algae. And you probably though it was just pond scum.


Quick Studies is an award-winning series that sheds light on new research and discoveries that change the way we look at the world.