Backpacks for Cells

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When they do reach the point of animal testing, the researchers plan to start by loading the backpacks with a trackable substance--perhaps the magnetic nanoparticles, which can be imaged by MRI, or perhaps fluorescent molecules. That will allow the team to determine how the cells migrate, and whether they reach the desired targets.

Eventually, Rubner and his colleagues envision using the backpacks for therapies that retool the body's own immune system to attack diseased or cancerous tissue. For example, immune cells could be removed from the bloodstream, equipped with backpacks, activated to home in on a tumor, and returned to the body. There, they would deliver their cargo--be it an imaging agent or a chemotherapeutic drug--directly to the tumor, sparing healthy tissues from exposure to the toxic payload.

The researchers initially expected that each backpack would adhere uniformly to its carrier cell's surface, much like a Band-Aid. Instead, the patches seemed to stick firmly at one spot, with the rest dangling off--sort of like a real backpack, which anchors only at the shoulders, says Rubner. This unexpected phenomenon might actually come in handy, he says. Immune cells need to squeeze through narrow openings in the body; a plastered-on pack might make cells less pliable, while a dangling pack could be pulled through.

For the most part, the cells and backpacks hooked up in a one-to-one ratio. But occasionally, under certain conditions, giant clumps of aggregated cells and backpacks formed. Because the backpacks didn't lie flat against the cells, more than one cell could latch on to a single patch, or more than one patch could attach to a cell. Rubner hopes that his team can learn how to manipulate this process, perhaps serving as a basis for bottom-up tissue engineering.

"This is a new approach," says Rubner. "There's a lot of flexibility in what you can do with it, and we're hopeful that flexibility is going to turn into something that's going to have great value for society."

"But that's going to take a while," he adds.