We found an interesting article titled ‘Quantum dots that emit infrared light open new window for biological imaging‘ on Phys.org that we thought would be good to share with you and keep you updated on the latest in nano-news!
At present, certain frequencies of short-wave infrared light is used to observe most biological tissues where they appear quite transparent due to the light. However, a new method is being developed by researchers who ‘have made tiny particles that can be injected into the body, where they emit those penetrating frequencies.’ This may open new possibilities in ‘making detailed images of internal body structures such as fine networks of blood vessels.’
The study is published in the journal Nature Biomedical Engineering, by MIT research scientist Oliver Bruns, recent graduate Thomas Bischof PhD ’15, professor of chemistry Moungi Bawendi, and 21 others. Their findings on the use of light-emitting particles called quantum dots shows a promising future.
At present, near-infrared imaging uses wavelengths between 700 and 900 nanometres, but the new near-infrared imaging works around wavelengths of 1,000 to 2,000 nanometres, providing better results as the body tissues appear more transparent in this range of light. ”We knew that this imaging mode would be better’ than existing methods, Bruns explains, ‘but we were lacking high-quality emitters’ – that is, light-emitting materials that could produce these precise wavelengths.’
Bawendi, the Lester Wolf Professor of Chemistry is a specialist at producing quantum dots, which his lab has been developing over the years. ‘These nanocrystals, made of semiconductor materials, emit light whose frequency can be precisely tuned by controlling the exact size and composition of the particles.’
The important factor was to develop these quantum dots whose emissions matched the ideal short-wave infrared frequencies and was bright enough for easy detection through the surrounding skin and muscle tissues. ‘The team succeeded in making particles that are ‘orders of magnitude better than previous materials, and that allow unprecedented detail in biological imaging,’ Bruns says. The synthesis of these new particles was initially described in a paper by graduate student Daniel Franke and others from the Bawendi group in Nature Communications last year.’
These light-emitting particles that the research team produced are quite bright, making it possible for the quantum dots to be captured with very short exposure times. It also opens up the possibility of video capture rather than single images, that would show the motion in detail such as the flow of blood, allowing the veins and arteries to be distinguished.
Bruns explains that the new quantum dots are the first light-emitting particles that allowed the imaging of awake and moving mice in contrast to the previous methods where the mice had to be anesthetised. Moving forward, the initial applications will be done at a preclinical research level on animals, as the compounds contain certain materials disapproved for use on humans. The researchers are working on making versions safer for human use.
The research also relies on ‘the use of a newly developed camera that is highly sensitive to this particular range of short-wave infrared light.’ Bruns explains that the camera is a commercially developed product and his team was the first customer for its specialised detector made of indium-gallium-arsenide. ‘Though this camera was developed for research purposes, these frequencies of infrared light are also used as a way of seeing through fog or smoke.’
Not only can the new method determine the direction of blood flow, Bruns says, it is detailed enough to track individual blood cells within that flow. ‘We can track the flow in each and every capillary, at super high speed,’ he says. ‘We can get a quantitative measure of flow, and we can do such flow measurements at very high resolution, over large areas.’
Such imaging could potentially be used, for example, to study how the blood flow pattern in a tumor changes as the tumor develops, which might lead to new ways of monitoring disease progression or responsiveness to a drug treatment. ‘This could give a good indication of how treatments are working that was not possible before,’ he says.
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