March 29, 2012 - We humans tend to think about our immune system only when it fails and we come down with a cold or flu. But every day that we walk around healthy, it's because white blood cells are waging a tireless war on bacteria, viruses, and parasites that invade our bodies, tracking down these foreign agents in the body and eliminating them.
Any defense can get overwhelmed, though, and our immune system is no exception. That's why a growing number of researchers are trying to improve on nature and develop their own white blood cells—and maybe learn a bit about how our own cells work in the process.
Daniel Hammer, professor of chemical engineering and biological engineering at the University of Pennsylvania, is building white blood cells in the lab from plastics that can act as artificial cell walls. Think of a gel capsule of your preferred headache medicine but on a much smaller scale and with a programmable molecular brain. These synthetic cells, known as leuko-polymersomes, could one day deliver the latest cancer-killing drugs directly to a tumor or send out a chemical beacon that signals natural white blood cells to come and join the fight against a disease.
"Ultimately I think that we could program these cells to do things that we never thought white blood cells could do," Hammer says. Instead of boosting immune response, for example, Hammer envisions synthetic cells that could act as inhibitors to the body's defenses, providing relief for people suffering from autoimmune disorders.
Hammer has been studying how to turn plastics into cellular structures for more than a decade, but it's just in the past few years that the field has kicked into high gear. His team is learning to mimic the targeting capabilities that let natural white blood cells take the fight to viruses and bacteria—what Hammer describes as a kind of "molecular zip coding"—and the adhesive properties that let them stand their ground when they arrive. In 2010, Hammer and colleagues from Duke University designed synthetic molecules shaped like the receptors white blood cells use to find and adhere to inflamed tissue. In-vitro tests showed that synthetic cells could seek out inflamed tissue and stick to it once they arrived.
That's only part of the process, however. Once a leuko-polymersome has adhered to an infected cell, it needs to release its medicinal payload. Last year, Hammer's team collaborated with researchers from the University of Delaware to show that a blast of UV light could prompt these biodegradable plastics to unravel and release their contents. That's an early step toward synthetic cells that could be programmed to release their contents on cue.
Hammer's synthetic white blood cells aren't the only drug-delivery device taking cues from nature. At UCLA, Tim Deming and his team are among the growing number of scientists taking their inspiration from some of nature's most notorious bad guys: viruses.
Read the rest of this article online at Popular Mechanics' webpage!