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Tiny Rockets Zoom into Blood to Capture Cancer Cells
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Micro-rockets for capturing cancer cells. The micro-rockets are fueled by hydrogen peroxide and are propelled by an exhaust of oxygen bubbles. These tubes are coated with antibodies that allow them to latch onto cancer cells. CREDIT: S. Balasubramanian et al., Angewandte Chemie. |
Blasting through blood samples like a missile roaring through the sky, a new breed of microscopic rocket searches out cancer, propelled by chemical boosters. Designed by scientists to speed up the identification of chemicals, these tiny rockets take the power of the space age down to the nanoscale.
The micro-rockets consist of tapered metal tubes 60 microns long, or about two-thirds the width of a human hair. Their interiors are lined with platinum, a metal that breaks down hydrogen peroxide, a common ingredient of bleach. This generates oxygen bubbles that naturally rush out each tube's wider end -- jet propulsion for speeds of roughly 85 microns per second.
"This is the first time we showed we can propel micro-rockets in biological media like blood," said Joseph Wang, a nanoengineer at the University of California, San Diego, "In the future, we can think of putting other receptor molecules on these micro-rockets to capture other targets of interest."
An iron layer sandwiched between the
of the roughly 5-micron-wide tubes lets the researchers steer the rockets using magnetic fields.
Time-lapse images showing the motion of a micro-rocket in human blood serum at two-second intervals.
CREDIT: S. Balasubramanian et al., Angewandte Chemie.
CREDIT: S. Balasubramanian et al., Angewandte Chemie.
The outer surfaces of these microtubes are platforms onto which the scientists can chemically attach antibodies, the molecules our immune system employs to latch onto and tag invaders. The researchers use these antibodies to bind the microtubes onto specific targets, such as a protein known as carcinoembryonic antigen, which is found in overly large amounts in approximately 95 percent of colorectal, gastric and pancreatic cancers.
In tests with human blood serum where scientists added hydrogen peroxide, pancreatic cancer cells and noncancerous immature white blood cells, the micro-rockets latched onto their cancerous targets 70 percent of the time, zipping around even while carrying their prizes with only a slight drop in speed. The microtubes did not bind the same way to noncancerous cells when rubbed against them.
These micro-rockets could serve as a novel way to capture relatively rare circulating tumor cells for cancer diagnosis tests without the substantial preparation of blood samples needed for other techniques that exist for isolating and counting these cells.
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