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The Buzz About Plastic Antibodies

We know scientists can manipulate the most basic units of life in the lab. Now they've made plastic copies of our body's natural defenders, antibodies.

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Courtesy of Hoang Xuan Pham, University of California, Irvine
UC Irvine chemistry professor Dr. Kenneth Shea recently reported in the Journal of the American Chemical Society that this plastic antibody rescued mice that had been exposed to lethal doses of melittin, the toxic component in bee venom.

How did scientists manage to make more of these biological bodyguards without using any living organisms?
I decided to call Shea for some answers.

In a nutshell, antibodies are produced by the immune system and they circulate in the bloodstream. Antibodies seek out and bind to foreign invaders, also known as "antigens," so they can be cleared out.

Because antibodies are great at finding and binding specific proteins, they can be very useful in medicine.

"They are now being produced and used therapeutically as drugs," Shea said. "They are used to bind to a specific protein that will alter a biological response and prevent something from happening...they can help alleviate the symptoms or cure certain disease states."

In fact, antibody therapy is already used to treat certain cancers.

However, growing up large quantities of a particular antibody that binds to a specific antigen is expensive and labor-intensive. Before antibodies can be used in the lab or in pharmaceuticals, their DNA needs to be sequenced. After that, they need to be grown up in cells or animals in the lab, extracted from their hosts, and purified.

Shea's team took a different approach to making antibodies.

They used a technique called molecular imprinting. It's a lot like plaster casting, but at a much smaller scale.

It works like this: Imagine that we needed to build something that would fit your right hand perfectly. That sounds easy enough. We could cover your hand with plaster: on your palm, on the back, and in between and around fingers. After it dried, you could wiggle your hand out and we'd be left with a fitted plaster cast of your hand.

Shea's team used melittin molecules as a template and a cocktail of small molecules, known as "monomers," as plaster. After an hour or two, the monomers would solidify, or "polymerize," and the toxin template could be removed.

The scientists were left with a collection of gloves that enveloped melittin perfectly.

Shea's lab injected these miniature gloves, also known as synthetic polymers, in mice that had been given lethal doses of melittin. Given the right concentrations of these plastic antibodies, some mice actually survived. These small structures were able to latch onto these toxic molecules and prevent them from doing damage to cells.

Shea hopes that molecular imprinting will allow scientists to make useful antibodies much faster and at a lower cost. The polymerization reaction, also known as the solidification step, takes only a few hours. Meanwhile, the process of harvesting antibodies from animals usually takes a few weeks.

Still, it will be some time before we start seeing these plastic antibodies used clinically.

Because these nanoparticles don't degrade, the scientists still have to investigate whether any toxicities or long-term side effects exist.

Also, a lot of research is involved in synthesizing one antibody. Scientists need to learn more about the antigen they are targeting so that they can select the right synthetic molecular ingredients to use. As with any good recipe, the amounts of each of these ingredients need to be refined several times.

It will be interesting to see what scientists serve up next.

Intern Rebecca Cheung is a graduate student at the University of British Columbia's School of Journalism.
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