Nanoscale Sensing of Temperature and Viscosity Inside Single Cells

Monitoring multiple modalities simultaneously within a cell remains a technical challenge. Fluorescent nanodiamonds (FNDs) with negatively-charged nitrogen-vacancy (NV) centers, are versatile sensors that can be used to measure different modalities including magnetic field, temperature and quantum nuclear magnetic resonance. [1] Unlike dye based thermometry systems, FNDs have consistency in measurements across environmental factors such as pH, ion concentration and refractive index. NV centers have high optical stability and do not undergo photo-bleaching. We have previously shown FNDs to have both cellular uptake and low cytotoxicity making them a suitable biocompatible sensor for invitro measurements. [2]<br/><br/>Building on our previous results, we now propose using FNDs to simultaneously measure temperature and viscosity within a living cell. Nano-thermometry is achieved by measuring the frequency shift of optically detected magnetic resonance (ODMR) of the NV- center. Local temperature can be measured with high spatial resolution within a single cell and FNDs can be functionalised to target specific regions in a cell, such as the mitochondria, facilitating in situ probing of biological processes. Simultaneously, viscosity measurements are achieved by tracking the movement of the FND inside the cell.<br/><br/>Currently, the inhomogeneous temperature distribution within a single cell remains controversial. Understanding the relationship between temperature, viscosity and the inner workings of a cell would provide insight into many biological processes, including, heat exchange among different organelles. We present our latest data on nanoscale sensing of temperature and viscosity in living systems.<br/><br/>References:<br/>Nanoscale NMR Spectroscopy Using Nanodiamond Quantum Sensors. Physical Review Applied 13, 044004 (2020);<br/>Graphitic and oxidised high pressure high temperature (HPHT) nanodiamonds induce differential biological responses in breast cancer cell lines. Nanoscale 10, 12169 (2018).