Quantum sensors made from a glowing protein can be produced by living cells and could be used to much more accurately measure tiny changes in the body. This could one day help with early disease detection or tracking how cells form.
Sensors based on the quantum mechanical property of spin can measure temperature, magnetic fields and other phenomena much more sensitively than conventional devices. They have already been shown to work in living animals, such as detecting the magnetic fields inside a rat heart or from mouse neurons.
These methods are based on diamonds that contain a microscopic defect that makes their spin interact with external magnetic fields, making the diamonds glow in a measurable way. While these devices are sensitive, no one has yet been able to target them at specific cellular processes.
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Now, at the University of Chicago and his colleagues have developed a quantum sensor made from a common fluorescent protein used in biological research, called enhanced yellow fluorescent protein (EYFP).
鈥淵ou want to get something to the few nanometre scale that鈥檚 biocompatible,鈥� says Awschalom. 鈥淵ou could try and manufacture a molecular system and make it biocompatible, that鈥檚 one route. The other route is to start with something that is biological, like a protein.鈥�
To make the protein act as a quantum sensor, Awschalom and his colleagues fired a blue laser at the fluorophore, the light-sensitive compound within it, to temporarily change the spin of its electrons. This spin state lasts for a few milliseconds, long enough to be affected by any external forces like electric fields or temperature changes, which can then be read out by a different, red laser.
The researchers then tested the sensor at -193掳C (-315掳F), about the working temperature of cryo-electron microscopes, which can be used to study frozen biological samples at a molecular level, using human kidney cells that were modified to produce EYFP. They showed that its quantum properties could be precisely controlled using microwaves and measured using the red laser.
They also produced the protein sensor in a solution at room temperature and showed that it was stable. 鈥淚t鈥檚 amazing you can coherently control a spin in a protein at room temperature,鈥� says at Heriot-Watt University in Edinburgh, UK.
While Awschalom and his colleagues didn鈥檛 measure any biological properties in their study, they hope the sensor could eventually be used for early disease detection or tracking cell formation processes, because EYFP is widely used as a biological tracker.
EYFP, which is modified from a glowing protein first extracted from the bioluminescent crystal jelly (Aequorea victoria), can be tacked on to any protein produced inside a cell by genetically modifying the cell鈥檚 protein production processes. The protein鈥檚 location can then be tracked using its fluorescent properties.
鈥淵ou鈥檝e got the ability to use both the illumination and microwave control to not just see the positions of where they are, but to sense the magnetic environment around these proteins,鈥� says Gauger. 鈥淵ou鈥檙e piggybacking on what people know how to do well, but it gives you a whole wealth of additional potential information.鈥�
arXiv
