To accurately diagnose and treat disease, doctors and researchers must look inside the body. Medical imaging tools have come a long way from the humble X-ray, but most existing tools are still too coarse to quantify the number or specific types of cells inside the body’s deep tissues.
Quantum dots can do this, according to new research in mice from the University of Illinois.
“Quantum dots can measure things in the body that are very, very dynamic and complicated that we cannot see right now. They allow us to count cells, discover their exact locations, and observe changes over time. I think it’s a really big breakthrough, “said Andrew Smith, a professor at U in I’s Department of Bioengineering and co-author of the study. ACS Nano examination.
Quantum dots are laboratory-grown nanoparticles – just a few hundred atoms – with special optical properties that can be detected by standard microscopy, tomography (eg PET / CT scanners) and fluorescence imaging. Depending on their size and composition, bioengineers like Smith can make them glow in certain colors and emit light in the infrared spectrum.
“Infrared light is rare. Very little light is emitted from tissues in the infrared, so if you put them in the body, they appear very bright. We can look deep into the body and can measure things more accurately than we ever could. to use technology in the visible domain, ”says Smith.
In it ACS Nano study, Smith and his colleagues dropped quantum dots on macrophages.
When our body has to swallow pathogens or clean up cell debris, macrophages start working. One of their tasks is to trigger inflammation, which makes the environment inhospitable to harmful microbes. But sometimes they do this job too well. Depending on the tissue they are in, chronic inflammation due to macrophage activity can lead to diabetes, cardiovascular problems, cancers and more.
The U of I team was particularly interested in macrophages in adipose or adipose tissue.
“With weight gain and obesity, it is known that the number of macrophages increases in adipose tissue and tends to develop towards an inflammatory phenotype, which contributes to the development of insulin resistance and metabolic syndrome. The number and location of macrophages in adipose tissue are poorly described, especially in vivo, ”says Kelly Swanson, Kraft Heinz Society Endowed Professor of Human Nutrition at the Department of Animal Science at the University of the Island and co. – author of the study.
“The quantum dots developed by our group allow better quantification and characterization of the cells in adipose tissue and their spatial distribution,” he adds.
The team created quantum dots coated with dextran, a sugar molecule that also targets macrophages in adipose tissue. As proof of concept, they injected these quantum dots into obese mice and compared the imaging results with dextran alone, the current standard for macrophage imaging.
Quantum dots performed better than dextran alone on all imaging platforms, including some optical techniques.
“Quantum dots emit an enormous amount of light, allowing us to further measure specific cell types and identify where they are,” says Smith. “This degree of light output allows the use of optical techniques, which are much more accessible than other imaging technologies. Compared to MRI and PET scanners, they are inexpensive instruments that can be installed in a small clinic. Everyone could have one.”
Although quantum dots have not yet been used in humans, Swanson sees a future where simple optical technology such as ultrasound can be used to non-invasively diagnose and detect inflammatory macrophages in obese patients.
“There could be a device like an ultrasound where you scan someone, and even if a patient’s weight has not changed, a doctor can tell if the cell types are changing. Several inflammatory cells could predict insulin resistance and other problems,” he says. “That’s why I’m interested in it, for its diagnostic properties. »
Quantum dots are not used in humans because they are usually made of heavy metals such as cadmium and mercury, and scientists have still not figured out how to metabolize and eliminate them from the body. Smith and his team work on quantum dots made with safer elements, but until then, they remain an invaluable research tool. For example, their long circulation time – nine times longer than dextran in the current study – could give diagnosticians a way to go beyond a snapshot in time.
“There is a huge level of macrophage variability even during a day. Adipose tissue can have a very high number in the middle of the day, and then it drops dramatically,” says Smith. “In animal experiments we can sacrifice animals at the beginning and end of one day to study the trend, but with quantum dots we may not have to.You can follow an animal over time to see its progress.
“Quantum dots offer enormous value in animal experiments. So even though quantum dots do not reach humans if we never find a way to make them non-toxic, the value is still very high.”
Smith, Swanson, and other colleagues recently received a grant from the National Institutes of Health to expand their work on quantum dots to target dozens of different cell types.
The Department of Animal Science is part of the College of Agricultural, Consumer, and Environmental Sciences at the University of Illinois at Urbana-Champaign.