Researchers in the Faculty of Applied Science & Engineering have built a set of magnetic "tweezers" that can position a nano-scale bead inside a human cell in three dimensions with unprecedented precision. The nano-bot has already been used to study the properties of cancer cells, and could point the way toward enhanced diagnosis and treatment.
Professor Yu Sun and his team have been building robots that can manipulate individual cells for two decades. Their creations have the ability to manipulate and measure single cells - useful in procedures such as in vitro fertilization and personalized medicine. Their latest study, published today (3/13) in Science Robotics, takes the technology one step further.
"So far, our robot has been exploring outside a building, touching the brick wall, and trying to figure out what's going on inside," says Sun. "We wanted to deploy a robot in the building and probe all the rooms and structures."
The team has created robotic systems that can manipulate sub-cellular structures inside electron microscopes, but that requires freeze-drying the cells and cutting them into tiny slices. To probe live cells, other teams have used techniques such as lasers or acoustics.
"Optical tweezers - using lasers to probe cells - is a popular approach," says Xian Wang, the PhD candidate who conducted the research. The technology was honoured with the 2018 Nobel Prize in Physics, but Wang says the force that it can generate is not large enough for the mechanical manipulation and measurement he wanted to do.
"You can try to increase the power to generate higher force, but you run the risk of damaging the sub-cellular components you're trying to measure," says Wang.
The system Wang designed uses six magnetic coils placed in different planes around a microscope coverslip seeded with live cancer cells. A magnetic iron bead about 700 nanometres in diameter - about 100 times smaller than the thickness of a human hair - is placed on the coverslip, where the cancer cells easily take it up inside their membranes.
Once the bead is inside, Wang controls its position using real-time feedback from confocal microscopy imaging. He uses a computer-controlled algorithm to vary the electrical current through each of the coils, shaping the magnetic field in three dimensions and coaxing the bead into any desired position within the cell.
