On their microfluidic chip, Nagrath's team grew dense forests of molecular chains, each equipped with an antibody to grab onto cancer cells.
Even after the cells are caught, it's still hard to run a robust analysis on just a handful of them, the researchers say. That's why this demonstration of highly sensitive tumor cell capture, combined with the ability to grow the cells in the same device, is so promising.
Hyeun Joong Yoon, a postdoctoral researcher in the Nagrath lab with a background in electrical engineering, was instrumental in making the microfluidic chip. He started with a silicon base and added a grid of nearly 60,000 flat gold shapes, like four-petaled flowers, each no wider than a strand of hair.
The gold flowers naturally attracted a relatively new material called graphene oxide. These sheets of carbon and oxygen, just a few atoms thick, layered themselves over the gold. This layered formation allowed the team to grow the tumor-cell-catching molecular chains so densely.
"It's almost like each graphene has many nano-arms to capture cells," Nagrath said.
To test the device, the team ran one-milliliter samples of blood through the chip's thin chamber. Even when they had added just three-to-five cancer cells to the 5-10 billion blood cells, the chip was able to capture all of the cells in the sample half the time, with an average of 73 percent over 10 trials.
"That's the highest anybody has shown in the literature for spiking such a low number of cells," Nagrath said.
The team counted the captured cancer cells by tagging them with fluorescent molecules and viewing them through a microscope. These tags made the cancer cells easy to distinguish from accidentally caught blood cells. They also grew breast cancer cells over six days, using an electron microscope to see how they spread across the gold flowers.
"When you have individual cells, the amount of
|Contact: Kate McAlpine|
University of Michigan