(a) Illustration of the structure of a quantum nanodiamond sensor coated with a pyrogenic polymer, and how it works as a hybrid nanocomputer / thermometer. (b) Image of electron microscope of hybrid sensors. (c) Working principle of a hybrid sensor for measuring nanometric thermal conductivity. In a medium with high thermal conductivity, the temperature rise of the diamond sensor is moderate, as the heat is easily dissipated. In contrast, the temperature rise in the medium with low thermal conductivity is significantly higher. The thermal conductivity inside cells can be determined by measuring the temperature change of hybrid sensors in cells. Credit: University of Osaka
An international team of researchers has created nanodiamond sensors that can act as heat sources and thermometers, and is being used to measure the thermal conductivity inside living cells, which could lead to new diagnostic tools and cancer therapies.
A team of scientists from the University of Osaka, the University of Queensland and the Faculty of Engineering at the National University of Singapore used tiny nanodiamonds coated with a heat-releasing polymer to test the thermal properties of the cells. When irradiated with light from the laser, the sensors acted as heaters and thermometers, allowing them to calculate the thermal conductivity inside a cell. This work could lead to a new set of heat-based treatments to kill bacteria or cancer cells.
Although the cell is the basic unit of all living things, certain physical properties are difficult to study in vivo. For example, the thermal conductivity of a cell, as well as if one side is hot while the other side is hot while the other side is cold, was mysterious. This gap we know is important for the development of thermal therapies targeting cancer cells and for answering basic questions about cell functioning.
(a) Temperature increases observed with hybrid sensors in air, water, oil, and inside the cell. These results are consistent with the idea that larger temperature rises occur in solvents with lower thermal conductivity. The literature values for the thermal conductivity of air, water and oil are 0.026, 0.61 and 0.135 W / m * K, respectively. (b) with a hybrid sensor inside the bright field microscopic image of a HeLa cell. Credit: University of Osaka
Now, the team has developed a technique for determining the thermal conductivity inside living cells with a spatial resolution of about 200 nm. They created tiny diamonds coated with a polymer, polydopamine, that fluorescent lasers emit fluorescent light and heat. Experiments showed that these particles are non-toxic and can be used in living cells. Inside a liquid or cell, heat raises the temperature of the nanodiamond. In high thermal conductivity media, the nanodiamond was not very hot because the heat escaped quickly, but in a low thermal conductivity environment the nanodiamonds were hotter. Basically, the properties of the emitted light depend on the temperature, so the research team could calculate the heat flow around the sensor.
Having a good spatial resolution allowed measurements to be made at different locations within the cells. “We found that the diffusion rate of cell heat, as measured by hybrid nanosensors, was several times slower than in pure water, a wonderful result that still awaits a broad theoretical explanation and depends on location,” said lead author Taras. Plakhotnik says.
“In addition to improving heat-based treatments for cancer, we believe that potential applications for this work will better understand metabolic disorders, such as obesity,” says author Madoka Suzuki. This tool can also be used for basic cell research, for example, to monitor biochemical reactions in real time.
Reference: “Bertan Measurements of thermal conductivity inside cells heating thermometer with hybrid diamond nanosensors “January 15, 2021, Advances in Science.
DOI: 10.1126 / sciadv.abd7888