Scientists have developed a wearable device that can continuously collect live cancer cells directly from a patient's blood, paving the way for doctors to diagnose cancer without conducting biopsies.
Tumours can release more than 1,000 cancer cells into the bloodstream in a single minute. Current methods of capturing cancer cells from blood rely on samples from the patient -- usually no more than a tablespoon taken in a single draw.
Some blood draws come back with no cancer cells, even in patients with advanced cancer, and a typical sample contains no more than 10 cancer cells.
"Nobody wants to have a biopsy. If we could get enough cancer cells from the blood, we could use them to learn about the tumour biology and direct care for the patients," said Daniel F Hayes, a professor at the University of Michigan in the US.
Over a couple of hours in the hospital, the device could continuously capture cancer cells directly from the vein, screening much larger volumes of a patient's blood.
In animal tests, the cell-grabbing chip in the wearable device trapped 3.5 times as many cancer cells per millilitre of blood as it did running samples collected by blood draw.
"It's the difference between having a security camera that takes a snapshot of a door every five minutes or takes a video. If an intruder enters between the snapshots, you wouldn't know about it," said Sunitha Nagrath, who led the development of the device.
Research shows that most cancer cells can not survive in the bloodstream, but those that do are more likely to start a new tumour.
Typically, it is these satellite tumours, called metastases, that are deadly, rather than the original tumour.
This means, cancer cells captured from blood could provide better information for planning treatments than those from a conventional biopsy.
Researchers injected healthy adult animals with human cancer cells, which are eliminated by the dogs' immune systems over the course of a few hours with no lasting effects.
For the first two hours post-injection, the dogs were given a mild sedative and connected to the device, which screened between 1-2 per cent of their blood.
At the same time, the dogs had blood drawn every 20 minutes, and the cancer cells in these samples were collected by a chip of the same design.
The device shrinks a machine that is typically the size of an oven down to something that could be worn on the wrist and connected to a vein in the arm.
"The most challenging parts were integrating all of the components into a single device and then ensuring that the blood would not clot, that the cells would not clog up the chip, and that the entire device is completely sterile," said Tae Hyun Kim, who earned his doctorate in the Nagrath Lab and is now a postdoctoral scholar at the California Institute of Technology.
The team developed protocols for mixing the blood with heparin, a drug that prevents clotting, and sterilisation methods that killed bacteria without harming the cell-targeting immune markers, or antibodies, on the chip.
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