There's a good chance that in the future, microscopic robots could be swimming and crawling their way through our bodies to deliver drugs or fight infections. While some of these have been capable of manipulating individual cells, researchers at the University of Toronto have developed a new way to get nano-scale probes inside cells, and precisely control them once they're in there.

One of the most common methods of probing live cells is what's known as "optical tweezers," where the radiation pressure of laser light is used to trap and move cells or bacteria. This technique is incredibly useful and even earned its creators the 2018 Nobel Prize in Physics, but according to the researchers on the new study, it has its limits. In order to generate higher forces to make more precise movements, you'd have to crank up the power of the lasers, but that risks damaging the cells.

So the Toronto team made their new system move magnetically. The "nanobot" is basically just an iron bead about 700 nm wide, which is small enough to be taken up by cells. Once inside, it can be steered by finely tuning a magnetic field surrounding the cell.

To demonstrate, the team placed the bead on a microscope coverslip along with live cancer cells, while six magnetic coils surround the microscope. After the bead is taken up by a cell, the researchers can move it in real-time using algorithms that vary the electrical current through each of the coils. That in turn changes the strength and shape of the magnetic field and pulls the bead in the desired direction.

In particular, the method can be used to study cell nuclei – the inner part of a cell that contains the genetic information – without having to remove them from cells, as is standard practice now. For example, the team studied the differences between early-stage and later-stage bladder cancer cells, discovering that the nucleus of a late-stage cell has a weaker stiffening response to prodding with the tiny bead compared to early-stage cells.

"In situations where early-stage cancer cells and later-stage cells don't look very different morphologically, this provides another way of telling them apart," says Wang.

As well as helping diagnose cancer, the system could lead to new approaches to fighting it.

"You could imagine bringing in whole swarms of these nano-bots, and using them to either starve a tumor by blocking the blood vessels into the tumor, or destroy it directly via mechanical ablation," says Yu Sun, lead researcher on the study. "This would offer a way to treat cancers that are resistant to chemotherapy, radiotherapy and immunotherapy."

The research was published in the journal Science Robotics.

View gallery - 3 images