Quantum measurement and orientation tracking of fluorescent nanodiamonds inside living cells

Abstract

Fluorescent particles are routinely used to probe biological processes. The quantum properties of single spins within fluorescent particles have been explored in the field of nanoscale magnetometry, but not yet in biological environments. Here, we demonstrate optically detected magnetic resonance of individual fluorescent nanodiamond nitrogen-vacancy centres inside living human HeLa cells, and measure their location, orientation, spin levels and spin coherence times with nanoscale precision. Quantum coherence was measured through Rabi and spin-echo sequences over long (>10 h) periods, and orientation was tracked with effective 1° angular precision over acquisition times of 89 ms. The quantum spin levels served as fingerprints, allowing individual centres with identical fluorescence to be identified and tracked simultaneously. Furthermore, monitoring decoherence rates in response to changes in the local environment may provide new information about intracellular processes. The experiments reported here demonstrate the viability of controlled single spin probes for nanomagnetometry in biological systems, opening up a host of new possibilities for quantum-based imaging in the life sciences.

Magnetic spin imaging under ambient conditions with sub-cellular resolution

“…At the expense of longer integration, scanning techniques such as stimulated emission depletion would boost Dr xy down to 8 nm 38 reaching even single spin sensitivities. Alternatively to our ensemble sensor, local spin densities could be monitored even inside living cells by employing single NVs embedded in nanodiamonds 39,40 . The high temporal resolution of widefield magnetometry favors sub-cellular visualization also of label-free dynamic processes, for instance the production of free radicals in cell death, the regulation of homoeostasis through ion channels 41 or haemoglobin trafficking by imaging paramagnetic oxygen.…”

Subdiffraction optical manipulation of the charge state of nitrogen vacancy center in diamond

“…This defect has the potential to be used for quantum computation, 1-4 nanoscale metrology [5][6][7][8] and biological imaging. [9][10][11] To further extend the study of the interaction between a multi-NV center and the nanoscale sensing with the NV center, it is necessary to detect and control the NV center spin-state dynamics with high spatial resolution. 7,[12][13][14] Therefore, many optical super-resolution microscopy techniques have been developed to detect single NV centers.…”

All-Optical Thermometry and Thermal Properties of the Optically Detected Spin Resonances of the NV– Center in Nanodiamond

“…[14][15][16][17][18] Furthermore, the center may be incorporated into nano-diamonds, whose chemical inertness and biocompatibility, allow sensing techniques to be performed within living cells. 19 Recently, the center's bio-sensing applications were expanded with the demonstration of sub-cellular temperature gradient mapping and control using NV − nano-diamond and gold nano-particles within a human embryonic fibroblast. 17 This exciting demonstration can be potentially extended to in vivo thermometry and thermoablative therapy.…”