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“The discovery of quantum dots has helped to catalyze the development of nanoscience”

Nanoparticles have not only found practical applications but have also ignited significant interest in the field of nanoscience and their potential applications in biology. Quantum dots have for instance the capability to label biological tissues, providing valuable insights into the various cellular structures.

The Nobel Prize in Chemistry this year has been awarded for the groundbreaking work on quantum dots (QDs). Nordic Life Sciences asked Dr. Heiner Linke, Professor of Nanophysics at the Physics Department at Lund University, and a member of the Nobel Committee for Chemistry, about these nanoparticles, their current potential and the scope they hold for the future.

Read more: Exclusive interview with Moungi Bawendi, Nobel Laureate in Chemistry 2023

What are quantum dots (QDs)?

“They are very small particles made by crystals that consist of just a few thousand atoms. If we imagine how small a soccer ball is compared to the entire planet Earth, a QD is that small compared to the soccer ball. In chemistry, colors arise from various molecules. However, with QDs, a distinctive mechanism is at play. In this case, it’s not the atoms that vary but rather the quantity of them that determines the resulting color. When a nanoparticle contains more atoms, it is bigger, emitting a redder color. Conversely, fewer atoms result in a smaller nanoparticle that emits a blue-shifted color. This phenomenon is fundamentally rooted in a quantum mechanical effect.”

 

 

Could you explain this further?

“QDs are typically made of semiconducting materials where the absorption of a photon can create a free electron. When an electron is confined to a compact space, its wave function becomes compressed. The crucial principle here is that the smaller the confinement, the higher the energy level of the electron. With increased energy, an electron can store more energy and impart more energy to a photon. Consequently, light emitted from a confined, small space tends to be bluer in color, while light from a more expansive space leans towards the redder end of the spectrum.”

When the ability to change a material’s properties by its size became accessible it captured people’s imagination due to the myriad of applications it could potentially offer.”

Why did the Nobel Prize Committee decide to give the award for QD research?

“One of the motivations is that the discovery of these nanoparticles generated a lot of interest in the field of nanoscience. I think it’s clear that this discovery helped to catalyze the development of nanoscience, and many people, chemists in particular, have become very interested. When the ability to change a material’s properties by its size became accessible it captured people’s imagination due to the myriad of applications it could potentially offer.”

 

Heiner Linke, Professor of Nanophysics, Physics Department, Lund University, and a member of the Nobel Committee for Chemistry. Photo: Kennet Ruona

 

Which biomedical applicability do QDs have?

“The most extensive use of QDs is for bioimaging. Due to its fluorescent properties, they are used for live cell imaging, which is the visualization of intracellular components, and also in vivo imaging for the visualization of organs and tissues. Also, when studying tumors, QDs can distinguish multiple species within the tumor milieu in vivo. Solid tumors are complex and composed of cancer and host cells embedded in an extracellular matrix and nourished by blood vessels. By dissecting and tracking these elements, researchers can gain deeper insights into the complex mechanisms at play in tumorigenesis and tumor progression.”

QDs can also be used as traceable drug delivery vectors for killing cancer cells. They travel through the blood vessel of a tumor and diffuse inside the cell due to the presence of enzymes, depositing the drugs into the tumor, for example in hepatocellular carcinoma and pancreatic cancer.”

“QDs can also be used as traceable drug delivery vectors for killing cancer cells. They travel through the blood vessel of a tumor and diffuse inside the cell due to the presence of enzymes, depositing the drugs into the tumor, for example in hepatocellular carcinoma and pancreatic cancer. Researchers can assess the drug delivery due to the fluorescence of the QDs. In medical diagnosis they can replace the classic contrast dyes and radioactive isotopes. They can be used to detect the Sentinel Lymph Node (SLN) during breast cancer operations, or even for the detection of micrometastases which occur in 30% of breast cancers.”

 

Left: Isolated quantum dots combined with antibodies and biosensors. Right: Cadmium sulfide quantum dots. Illustrations: iStock

 

What clinical trials exist regarding QDs?

“The clinical applicability of QDs is not yet happening but there exist a limited number of ongoing clinical trials. It’s an area that still requires extensive exploration and further research to fully unlock their capabilities. QDs need a close evaluation from a clinical perspective. However, there exist clinical trials such as a bioimaging and anticancer phase I study for breast and skin cancer, and other phase I and II studies where QDs are used as an immunologic monitoring tool for vaccines against type I Diabetes Mellitus.”

On a broader level we’ll continue seeing these nanoparticles as one kind of material, and its optical properties will be popping up everywhere.”

What is in the future scope?

“On a broader level we’ll continue seeing these nanoparticles as one kind of material, and its optical properties will be popping up everywhere. Regarding energy production we need sustainable methods. Solar power, for instance, is intermittent and requires complementing solutions like energy storage through batteries, which come with their own sustainability challenges. In this context, there is a significant need for efficient ways of producing solar fuels where QDs may play a role. One potential application is in water-splitting photocatalysis to produce hydrogen as a fuel. This process involves the dissociation of water into hydrogen and oxygen using a catalyst and light energy such as sunlight.”

Featured photo of Heiner Linke: Kennet Ruona

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About the author

Paula Pérez González-Anguiano, M.Sc. in Scientific, Medical and Environmental Communication, is a Science Journalist and Illustrator based in Barcelona, Spain.

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