Laser to light up tumours Alfred Pasieka/SPL

That warm glow inside could be more than a metaphor. Researchers are working on a laser made out of blood that would emit infrared light, allowing doctors to hunt down tumours.

The word “laser” conjures up images of complex electronics, but lasers can actually be made from a variety of materials, including living cells and jelly. To build a laser, all you need is an initial source of light, a material that amplifies it, and a reflective cavity.

Xudong Fan at the University of Michigan, Ann Arbor, and his colleagues are using a dye called indocyanine green (ICG) for their blood laser. It’s fluorescent in near-infrared light and is already injected into the bloodstream for use in medical imaging. Fan says turning it into a laser will make it glow much brighter.


Protein powered laser

The team found that ICG would not emit laser light by itself, but the dye will glow when mixed with blood as it binds to proteins in blood plasma, increasing its ability to amplify light. “Without blood, just ICG, it doesn’t work at all,” says Fan.

By placing this mixture in a small reflective cylinder and shooting it with a conventional laser, they were able to coax the blood to emit light.

ICG accumulates in blood vessels, so areas of the body with large numbers of vessels, such as tumours, should glow much more brightly, says Fan. In a clinical setting, doctors could inject ICG and shine a normal laser at the skin, then check for a glow using an infrared camera.

But first Fan needs to test the laser in animal tissue, which means coming up with a way to introduce reflective cavities to the body. Gold nanoparticles could prove useful, he says.

“Eventually, we are trying to do it in the human body,” says Fan, but they are ensuring that the laser output is lower than recommended safety limits. “You don’t want to burn the tissue.”