Nanodiamond in the rough

Much of the activity of living organisms occurs inside cells and can be challenging to observe and study. This is because living biological systems are inherently complex and feature transient dynamics among a range of interdependent parameters, such as nanometer-scale temperature and viscosity fluctuations.

Nanodiamonds can provide a sensing platform that promises to reveal these elusive cellular properties. Belser et al. showcased various nanodiamond quantum sensing modalities to convey the current state-of-the-art for this emerging technology and assess their challenges and potential future applicability.

“Nanodiamonds offer a unique, non-invasive way to investigate a plethora of properties inside living cells, from temperature and pH to viscoelasticity and magnetic fields,” said author Sophia Belser.

Nanodiamonds can be made as small as a few nanometers wide, and introducing a nitrogen-vacancy defect results in an associated quantum spin that is highly sensitive to external factors. As a versatile host for quantum sensors, diamond nanocrystals can be fully embedded in cells, tissues, or organisms of interest. When their quantum spin is activated through optical and microwave excitation, the sensors yield remarkable capabilities.

“This spin effectively acts as a qubit, like the qubits that are the building blocks of a quantum computer,” said author Helena Knowles. “The quantum nature of the sensor enables detection that is robust to fluctuations in background fluorescence and can measure multiple parameters simultaneously.”

The sensors can also detect nearby nuclear spins, essentially performing nanometer-scale nuclear magnetic resonance imaging.

“Also, they may shed light on the thermodynamic phase space and the metabolic activity landscape of biological systems at the nanometer scale,” said author Jack Hart.

Source: “Opportunities for diamond quantum metrology in biological systems,” by Sophia Belser, Jack Hart, Qiushi Gu, Louise Shanahan, and Helena S. Knowles, Applied Physics Letters (2023). The article can be accessed at http://doi.org/10.1063/5.0147469 .