Tracking of quantum sensors in living cells pave the way for advances in drug discovery and nanomedicine

Imagine this: A typical human cell is approximately 10-20 microns in size. That is about one-hundredth a millimetre, or one-tenth the diameter of a human hair.

Now, imagine a quantum sensor the size of an atom, encased in a nanodiamond 1000 times smaller than a typical human cell.

With those incredibly tiny pictures in mind, imagine those nanodiamonds moving around inside that typical human cell, with the quantum sensors inside the nanodiamonds relaying messages about the cell’s activity back to the research team.

Nanodiamond crystals

This groundbreaking research, led by Professor Lloyd Hollenberg from the School of Physics at the University of Melbourne, will help scientists gain a better understanding of cell function, and open up new possibilities for quantum-based imaging in the life sciences.

“It is exciting to see how the atom experiences the biological environment at the nanoscale”, Professor Hollenberg said.

Nanodiamonds inside the living cells

Not only did the researchers successfully track the movement of the nanodiamonds inside a living human cell, they also successfully tracked the rotation of nanodiamonds. With the nanodiamonds acting as both “a sensor and a compass”, the scientists were able to observe cell functions at a molecular level – something that has not been done before, according to Dr David Simpson, a research fellow in quantum sensing with the School of Physics.

Dr Simpson added that using the quantum sensors to track cell activity at the molecular level will help paint a better picture of how cells work.

“Up until now, we have a general understanding of how cells work, but this lets us get down to the molecules within the cell,” he said.

The atomic sensor is created by removing two carbon atoms from the diamond and replacing it with a single nitrogen atom – resulting in what is called a nitrogen-vacancy (NV) centre in the atomic structure of the nanodiamond.

Atomic structure of diamond with NV centre

Diamonds with NV centres are becoming increasingly popular for use in quantum sensing applications due to their extraordinary range of properties, including sustained fluorescence, which enables detection at the molecular level, and proven biocompatibility.

While previous research has explored the use of nanodiamonds with NV centres as fluorescent markers in cells, this is the first time that they have been used as a sensor to explore the nanoscale environment inside a living human cell. Other forms of fluorescent imaging, like the use of quantum dots, aren’t able to give the same type of information.

Another member of the research team, quantum physicist and PhD student Liam McGuinness, said that the ability to track activity at the molecular level could help biologists understand what cells do.

“We can follow single molecules within the cell to see what they do. We can observe the cell’s basic processes at the molecular level, which will help biologists better understand how cells function,” he said.

Achieving a better understanding of cells and how they function at the molecular level can also lead to future breakthroughs and advances in nanomedicine, as well as drug testing and development.

“This research paves the way towards a new class of atom sensors used for biological research into the development of new drugs and nanomedicine”, Professor Hollenberg said.

The research team comprised scientists from the university’s Physics, Chemistry, and Chemical and Biomolecular Engineering departments. It was funded by the ARC Centre of Excellence for Quantum Computation and Communication Technology, and was published in the journal Nature Nanotechnology in May.
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Main image: Nanodiamonds in living cells elucidating intra-cellular processes through quantum measurement