Nanodiamond thermometer to take temperature of individual cells

cell schematic

Researchers working at a lab at Harvard University have developed a technique that allows for taking the temperature of individual living cells. In their paper published in the journal Nature, the team describes their technique and just how precise temperature measurements taken with it can be.

The image shows an artistic representation of a novel technique for nanoscale temperature control inside of a living cell using techniques from quantum optics. The image depicts a rendering of a cell containing nanodiamonds and gold nanoparticles. A gold nanoparticle is heated by an external laser beam and nanodiamonds are used to probe the local temperature. Credit: Georg Kucsko

The new thermometer developed by the team follows work by other researchers who have found that single atom impurities in diamond crystals (which typically are replaced with a nitrogen atom and a vacancy gap) can be ultrasensitive to changes in temperature—such fluctuations can be seen as a hindrance when attempting to use such material to hold quantum bits, but in the biological world, they can be used to very precisely measure temperature.

In their research the team at Harvard injected a single nanodiamond (a diamond just 100 nm in size) into a human cell. (Read about the principles of measurement details) Once in place a green laser was shone onto the nanodiamond. Because it altered the spin state of an electron in the impurity, the light that was emitted was changed to red. The degree to which it was changed was then used to calculate the temperature of the interior of the cell. Following that experiment, the team injected two nanodiamonds into a single cell, then focused two separate green lasers onto them, then measured the red light that was emitted. This allowed them to measure the temperature difference between two locations in the same cell. Next, the team injected a nanodiamond and a gold particle into the cell. Once in place a green laser was shone onto the nanodiamond while another laser was shined onto the gold particle causing it to heat up. That heat was transferred to the rest of the cell and was subsequently measured by the nanodiamond.

Using this technique the researchers report being able to measure temperature fluctuations as small as 0.05 Kelvin—they expect to achieve better results in the future as temperature fluctuations as small as 0.0018 Kelvin have been recorded using the device outside of a cell. A thermometer with such precision could conceivably be used for both research purposes and in practical applications such as helping to distinguish (or kill) individual cancer cells inside the body.

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