WASHINGTON, March 13 (Xinhua) -- Canadian scientists developed a kind of magnetic "tweezers" that can precisely bring minuscule bead robot into live human cancer cell, pointing to a new option for diagnosing and killing cancer.

The study published on Wednesday 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 bead, about 700 nanometers in diameter, is placed on the microscope coverslip surrounded by six magnetic coils in different planes, and the cancer cell can swallowed the bead into its membrane, according to the study.

Then, the researchers from University of Toronto controlled the bead's position under a microscopy, 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 have to extract the cell nuclei to examine it.

The Canadian researchers 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 Sun Yu, a professor in the Department of Mechanical and Industrial Engineering at University of Toronto. "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 early stage though both are seemingly similar, according to the researchers.

Also, the researchers imagined using the tiny robots to either starve a tumour by blocking the blood vessels into the tumor, or destroy it directly through mechanical ablation, although those applications are still a long way from clinical uses.