Tiny magnets have been used to guide stem cells to repair injuries in a study that opens a new approach to targeted medicine.

Research by British scientists has shown that nanomagnets consisting of stem cells “tagged” with microscopic particles containing iron, each of which is 2,000 times smaller than the thickness of a human hair, can be steered around the body using an external magnetic field.

The first study of the technique has shown that it can boost by five times the number of stem cells that reach the injured blood vessels of rats.

The results also suggest that similar methods could be used in other branches of medicine, for example to guide chemotherapy drugs towards tumours while avoiding healthy tissue.

As the nanoparticles used in the experiment are already approved for medical use by the US Food and Drug Administration, human trials of the technology could potentially begin within three to five years, scientists said.

Mark Lythgoe, of University College London who led the study, said: “These particles are tiny: one nanometre is the distance that a fingernail grows in a second.”

“It’s feasible that heart attacks and other vascular injuries could eventually be treated using regular injections of magnetised stem cells.

“The technology could be adapted to localise cells in other organs and provide a useful tool for the systemic injection of all manner of cell therapies. And it’s not just limited to cells – by focusing tagged antibodies or viruses using this method, cancerous tumours could be much more specifically targeted.”

In the study, published in the Journal of the American College of Cardiology: Cardiovascular Interventions , the team focused on a type of stem cell called endothelial progenitor cells, which have been shown to be important in vascular healing.

Each cell was tagged with a “nanomagnet” about 50 nanometres in diameter, before these were injected into the rats. A magnetic field was then used to guide the tagged stem cells through the bloodstream until they reached an injured artery.

Panagiotis Kyrtatos, another member of the UCL team, said: “This research tackles one of the most critical challenges in the biomedical sciences today: ensuring the effective delivery and retention of cellular therapies to specific targets within the body.

“The nanomagnets not only assist with the targeting but with the aid of MRI (magnetic resonance imaging) also allow us to observe how the cells behave once they’re injected.”

Professor Peter Weissberg, medical director of the British Heart Foundation, which helped to fund the study, said: “This encouraging research shows that nanomagnets could be used to help therapeutic stem cells reach specific areas of the body, particularly inside blood vessels where the blood is flowing fast and at high pressure.

“We await further research to find out if, as well as increasing the chances of these cells getting to where they are needed, this strategy can actually speed up the repair process.”

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