Tracking cells within the human body could lead to a greater understanding of how certain cells work, particularly cancerous cells found in tumors. Several scientific teams have worked on trying to figure out how to light up those cells in a certain way so that they're easier to track and study.

Now, a team of researchers from the University of St. Andrews in Scotland have figured out how to insert tiny lasers into cells to light them up at different wavelengths so that scientists can easily track them in the human body.

"The ability to track the movement of large number of cells will widen our understanding of a number of important processes in biology," says St. Andrews professor Malte Gather. "For instance being able to see where and when circulating tumor cells invade healthy tissue can provide insight into how cancers spread in the body which would allow scientists to develop more targeted therapies in the future."

This isn't the first time scientists have made human cells glow. A few years ago, researchers from Massachusetts General Hospital accomplished the same thing by inserting a certain molecule, one often found in jellyfish, into a resonant cavity in each cell.

In their study, published in the journal Nano Letters, the St. Andrews team did something different, though: they inserted a small plastic bubble full of fluorescent dye into each cell, creating a resonant cavity. When a laser hits each cell, it activates the dye inside the bubble, making it bounce around and light up. In a lab, scientists have managed to get the dye to emit three different wavelengths.

Although previous studies used lasers to light up cells like this, the St. Andrews research marks the first time that scientists have used optical resonators for lasers that were small enough for insertion into a cell. This miniaturization plays an important part in the future of tracking human cells for further study.

"In the future, these new lasers can help us understand important processes in biomedicine," says Gather. "For instance, we may be able to track — one by one — a large number of cancer cells as they invade tissue or follow each immune cell migrating to a site of inflammation."

Of course, the current study only worked with cells in a petri dish. However, the St. Andrews researchers hope to expand the study to cells within the human body soon to track individual cells.