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Jellyfish-inspired tentacles capture cancer


Cells traveling through a microfluidic device can be trapped by strands of DNA (green). (Source: Rohit Karnik and Suman Bose)

Tiny strands of DNA that float like jellyfish tentacles can grab and hold tumour cells in the bloodstream, which may in the future help cancer patients fight the dreaded disease.

The device can be used to both count and sort cancer cells, which is an important indicator of how well chemotherapy or other treatments are working. Doctors need to know whether cancer cells are being knocked out or developing immunity.

"The key is to know which drugs the remaining cells would be most susceptible to," says Jeffrey Karp, an author on the paper published in the Proceedings of the National Academy of Sciences and co-director of the Center for Regenerative Therapeutics at Brigham and Women's Hospital in Boston.

"Often these cells in the blood stream are at very low concentrations and it's difficult to isolate them. What you really want to do is collect them and study the biology of the cells and subject them to different kinds of chemo so you know which one is best to use."

Karp says he's been stung by jellyfish before while swimming with his son: "It doesn't do much damage, but it really hurts."

The idea for the microchip came one day in the lab while brainstorming with one of his colleagues.

"We became inspired by jellyfish that have these long tentacles that extend far away from their main body," says Karp. "Regardless where the food lands, they can capture it."

They took short strands of DNA called aptamers that bind with the targeted cancer cell surface, then copied them hundreds of times using something called rolling circle amplification.

By connecting these aptamers, they came up with strands of material tens of microns long, much longer than the cell itself.

One end of the strand is connected to the microchip and the other floats free in the bloodstream. As the cancer cells drift by, the aptamers bind to them no matter where they touch, just like a jellyfish grabbing food, Karp explains.

During experiments, Karp and his team were able to capture 60 per cent of the cancer cells floating by, a figure higher than an existing method that uses a tiny magnet that binds to the cancer cell and is then picked up by a magnetized micro-sorter.

Turning to nature

In other projects, Karp has used the stickiness of gecko feet, the delicateness of spider webs and the spines of a porcupine to come up with new kinds of human medical devices.

"Often in technology we encounter barriers that appear to be insurmountable," Karp said. "Turning to nature, we can get ideas to think about and help us to think out of the box to new solutions far removed from standard approaches."

Professor Jeffrey Chalmers of Ohio State University, likes the idea.

"The jellyfish approach is interesting and the initial data looks promising," says Chalmers, an expert in cell-sorting technologies. "They did a decent job of selling me on it. I like the approach."

Chalmers says one of the challenges in any kind of cell-sorting is determining the identity of cancer cells. That's because cancer cells are often hard to distinguish from non-cancerous ones since they are both produced in the body.

Karp says the next step is to use the device to check for cancer cells in actual human patients.

Tags: health, cancer, dna