Canadian scientists have developed a kind of magnetic tweezer that can precisely insert a minuscule bead robot into a live human cancer cell, pointing to a new option for diagnosing and killing cancer.

The study, published in the journal Science Robotics, described the design in which a magnetic iron bead about 100 times smaller than the thickness of a human hair can be coaxed into any desired position within the cell, the Xinhua reported. The bead, about 700 nanometres in diameter, is placed on the microscope coverslip surrounded by six magnetic coils in different planes, and the cancer cell can swallow the bead into its membrane.

Then, the researchers from University of Toronto controlled the bead's position under a microscope, using a computer-controlled algorithm to vary the electrical current through coils and shaping the magnetic field in three dimensions. The researchers used their robotic system to study early-stage and later-stage bladder cancer cells. Previously, they had to extract the cell nuclei to examine it.

The team measured cell nuclei in intact cells instead of breaking apart the cell membrane, showing that the nucleus is not equally stiff in all directions. "It's a bit like a football in shape. Mechanically, it's stiffer along one axis than the other," said Professor Sun Yu. "We wouldn't have known that without this new technique."

They were able to measure how much stiffer the nucleus got when prodded repeatedly, and thus find out which cell protein or proteins might play a role in controlling this response, which could work as a new method of detecting cancer in early stage. In the later-stage cells, the stiffening response is not as strong as they are in the early stage, though both are seemingly similar, the researchers said. Also, the team visualised using the tiny robots to either starve a tumour by blocking its blood vessels, or destroy it directly through mechanical ablation, although those applications are still a long way from clinical uses.