Fluorescent Nanodiamonds—A Versatile Probe for Quantum Biosensing and Imaging

Nanodiamonds (NDs) are carbon-based nanomaterials that have attracted significant attention over the past decade. NDs provide a unique range of chemical, physical, and biological properties which have driven their application in the fields of drug delivery, tissue engineering, bioimaging and quantum biosensing¹. NDs hosting fluorescence color centres, referred to as FNDs, provide photostable emission, high quantum efficiency and often long fluorescent lifetimes when compared to other organic fluorophores used for cellular imaging. Several color centres are being explored as promising candidates in bioimaging including the nitrogen-vacancy (NV), silicon-vacancy (SiV) and germanium-vacancy (GeV) centres. Recent studies exploiting the quantum properties of the NV centre in FNDs have demonstrated the detection of magnetic^2,3, electric⁴, and temperature fields⁵, as well as pH⁶, redox⁷ and radical species^8-9. These quantum sensors therefore open up new and exciting opportunities to monitor biological activity at the nanoscale.<br/>In this work, I will outline our efforts in applying FND probes to a range of biological problems. I will describe how these materials can be used to enhance the detection limits of biological assays and be applied to probe the intracellular temperature of living cells⁵. I will discuss our recent work exploiting 2D NV imaging arrays for magnetic microscopy. In particular, I will show how these magnetic imaging techniques can be used to non-invasively map the magnetic properties of iron-oxide complexes in biological systems at the sub-cellular scale^10-11. I will also discuss the future possibilities of these technologies and how they might be applied to address significant and outstanding questions in biology.<br/><b>References:</b><br/>1. Barzegar Amiri Olia, et al., Advances in the Surface Functionalization of Nanodiamonds for Biological Applications: A Review. ACS Applied Nano Materials 2021, 4 (10), 9985-10005<br/>2. Kaufmann, S.et al., Detection of atomic spin labels in a lipid bilayer using a single-spin nanodiamond probe. <i>PNAS </i><b>2013,</b> <i>110</i>, 10894--10898.<br/>3. Shi, F. et al., Single-protein spin resonance spectroscopy under ambient conditions. <i>Science </i><b>2015,</b> <i>347</i> (6226), 1135-1138.<br/>4. Karaveli, S.et al., Modulation of nitrogen vacancy charge state and fluorescence in nanodiamonds using electrochemical potential. <i>PNAS </i><b>2016,</b> <i>113</i> (15), 3938-3943.<br/>5. Simpson, D. A.et al, Non-Neurotoxic Nanodiamond Probes for Intraneuronal Temperature Mapping. <i>ACS Nano </i><b>2017,</b> <i>11</i> (12), 12077-12086.<br/>6. Fujisaku, T.et al., pH Nanosensor Using Electronic Spins in Diamond. <i>ACS Nano </i><b>2019,</b> <i>13</i> (10), 11726-11732.<br/>7. Rendler, T. et al., Optical imaging of localized chemical events using programmable diamond quantum nanosensors. <i>Nat. Commun. </i><b>2017,</b> <i>8</i>, 14701.<br/>8. Barton, J. et al., Nanoscale Dynamic Readout of a Chemical Redox Process Using Radicals Coupled with Nitrogen-Vacancy Centers in Nanodiamonds. <i>ACS Nano </i><b>2020</b>.<br/>9. Nie, L et al., Quantum monitoring of cellular metabolic activities in single mitochondria. <i>Science advances </i><b>2021,</b> <i>7</i> (21), eabf0573.<br/>10. McCoey, et al., Quantum Magnetic Imaging of Iron Biomineralization in Teeth of the Chiton Acanthopleura hirtosa. <i>Small Methods </i><b>2020,</b> <i>4</i> (3), 2070010<br/>de Gille, et al., Quantum magnetic imaging of iron organelles within the pigeon cochlea, <i>PNAS</i>, <b>2021</b> <i>in press</i>.