If you are a fan of sci-fi like myself, believe in aliens like my boss does, or are a cat parent that likes to get in some cat-ercise, lasers are probably a big part of your life (or at least your cat’s).
But besides the occasional blaster or laser pointer, you may not think there is much application for lasers when it comes to medicine. However, Mass General researchers are showing the world just the opposite.
Sangyeon Cho, PhD, is a researcher in the lab of Seok Hyun (Andy) Yun’s at the Wellman Center for Photomedicine at Massachusetts General Hospital.
Cho and his colleagues have developed the world’s smallest lasers—so tiny they can color-code individual cancer cells to help study their movements.
But how does a laser do that? We interviewed Cho to find out more about the project.
Lighting the Way
Cho explained that when he first entered the world of cancer cell research, it was hard for researchers to tell each of the individual cells in the tumor microenvironment apart, making it difficult to learn what part each cell played in cancer growth over time.
“Biologists and medical scientists use microscopes to study billions of these individual cells, but the problem is that under an optical microscope, they all look similar, and they are constantly moving,” Cho explains.
Fluorescence is one way that researchers have been able to color code cells using light, but that process is limited to about a dozen colors in total because fluorescence involves many different wavelengths of light, which can lead to overlapping colors.
After much hypothesizing, the team realized a potential solution to this: Create pure color beams of light, or in this case—lasers—so that more colors can be used without overlapping.
Specifically, they wanted to create a laser that was small enough to fit inside the cells themselves, enabling them to give each cell a unique color code based on their composition and the size of lasers.
The approach could expand the potential color palate for cell coding to more than a billion colors.
But how do you make the laser smaller?
To make laser light from tiny particles, the light needs to be trapped in a small space inside the particle, where energy is added, and the laser process turns that energy into laser light.
Creating a laser this small has been a big challenge in photonics because the tiny particle is too small, and the light stays inside it for only a very short time.
Cho and his colleagues were able to create a half-wave laser having a size of 170 nanometers (nm) emitting 1060 nm wavelength of light (refractive index is 3.4).
For size reference, a human hair is about 100,000 nmwide, meaning you could fit over 500 of these lasers within the width of a single strand of human hair.
A key part of this process is adding gold to the semiconductor particle, which greatly improves the laser process and makes the light last longer.
Delivering them to the cells
After creating the nanolasers, the researchers then coat them in biocompatible silica and polymer (another innovation from the team), and then they are taken up by the cells they want to study.
Because every cell holds their laser in a unique way, each cell then emits a unique color or wavelength of light. By doing this, the researchers created a color-coding system to study each cell in real time.
So we have a laser light show, now what?
While Cho and fellow colleagues at the Yun lab have made great strides and improvements to the tiny lasers, the technology still has a lot more potential for future scientific applications as well.
It could eventually lead to being able to study a patient’s individual cancer cell’s movement, growth, and interactions.
Not only could this be the key to a better understanding of cancer, but it could also help researchers that are investigating many medical mysteries by giving them a new way to study living cell behavior and dynamic processes.
Eventually, Cho wants to be able to use the tiny lasers to not only color-code the cells, but also use the light emitted by them to study the individual molecules or subcellular organelles, such as mitochondria, within that cell.
While the researchers continue to push the boundaries of laser physics, the world's smallest lasers hold immense promise for advancing our comprehension of cellular behavior and illuminate the way for transformative advancements in medical research.
So next time you're watching Han Solo shoot his blaster first, just know that one day lasers could save you, too.
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