Nanolasers Light up Immune Cells

Tiny semiconductor nanodisk lasers allow cell-tracking through micro-pores, thus providing a powerful tool to study cell migration and cancer invasion. (Source: U. St. Andrews)

A team of researchers from the School of Physics at the University of St Andrews has developed tiny lasers that could revolu­tionize our under­standing and treatment of many diseases, including cancer. The research involved deve­loping miniscule lasers, with a diameter of less than a micrometer, and inserting them into live cells, e.g., immune cells or neurons. Once inside the cell, the lasers function as a beacon and can report on the location of cells, or poten­tially even send infor­mation about local conditions within a cell.

Currently, biologists typically use fluorescent dyes or fluores­cent proteins to track the location of cells. Replacing these with tiny lasers gives scientists the ability to follow a much greater number of cells without losing track of which cell is which. This is because the light generated by each laser contains only a single wave­length. By contrast, dyes generate light of multiple wave­lengths in parallel which means one cannot accurately distinguish the light from more than four or five different dyes – the colour of the dyes simply becomes too much alike. Instead, the researchers have now shown that it is possible to produce thousands of lasers that each generate light of a slightly different wave­length and to tell these apart with great certainty.

The new lasers, in the form of tiny disks, are much smaller than the nucleus of most cells. They are made of a semi­conductor quantum well material to provide the brightest possible laser emission and to ensure the colour of the laser light is compatible with the require­ments for cells. While lasers have been placed inside cells before, earlier demon­strations have occupied over one thousand times larger volume inside the cells and required more energy to operate, which has limited their application, especially for tasks like following immune cells on their path to local sides of inflam­mation or moni­toring the spread of cancer cells through tissue.

Malte Gather from the School of Physics and Astro­nomy said: “While it is exciting to think of cyborg immune cells that fight off bacteria with an on-board laser cannon, the real value of the latest research is more likely in enabling new ways of observing cells and thus better under­standing the mechanisms of disease.” Andrea Di Falco, who co-super­vised the project, added: “Our work is enabled by sophis­ticated nano­technology. A new nanofabri­cation facility here in St Andrews allows us to produce lasers that are among the smallest known to date. These inter­nalised sensors, akin to RFID micro­chips, permit to follow the cells as they feed, interact with their neighbours and move through narrow obstacles, without condi­tioning their behaviour.”

PhD student Alasdair Fikouras and Marcel Schubert, who jointly tested the new lasers, are very excited about the prospects of the new laser platform: “The new lasers can help us study so many urgent questions in completely different ways than before. We can now follow indi­vidual cancer cells to under­stand when and how they become invasive. It’s biology on the single cell level that makes it so powerful.” (Source: U. St. Andrews)

Reference: A. H. Fikouras et al.: Non-obstructive intracellular nanolasers, Nat. Commun. 9, 4817 (2018); DOI: 10.1038/s41467-018-07248-0

Link: Synthetic Optics Group, School of Physics and Astronomy, University of St Andrews, St Andrews, Scotland, UK

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