Dynamic Quantum Sensing of Paramagnetic Species Using Nitrogen-Vacancy Centers in Diamond

Abstract

Naturally occurring paramagnetic species (PS), such as free radicals and paramagnetic metalloproteins, play an essential role in a multitude of critical physiological processes including metabolism, cell signaling and immune response. These highly dynamic species can also act as intrinsic biomarkers for a variety of disease states whilst synthetic paramagnetic probes targeted to specific sites on biomolecules enable the study of functional information such as tissue oxygenation and redox status in living systems. The work presented herein describes a new sensing method that exploits the spin dependent emission of photoluminescence (PL) from an ensemble of nitrogen vacancy centers in diamond for rapid, non-destructive detection of PS in living systems. Uniquely this approach involves simple measurement protocols that assess PL contrast with and without the application of microwaves. The method is demonstrated to detect concentrations of paramagnetic salts in solution and the widely used magnetic resonance imaging contrast agent Gadobutrol with a limit of detection of less than 10 attomol over a 100 µm x 100 µm field of view. Real time monitoring of changes in the concentration of paramagnetic salts is demonstrated with image exposure times of 20 ms. Further, dynamic tracking of chemical reactions is demonstrated via the conversion of low spin cyanide coordinated Fe 3+ to hexaaqua Fe 3+ under acidic conditions. Finally, the capability to map paramagnetic species in model cells with sub-cellular resolution is demonstrated using lipid membranes containing gadolinium labelled phospholipids under ambient conditions in the order of minutes. Overall, this work introduces a new sensing approach for the realization of fast, sensitive imaging of PS in a widefield format that is readily deployable in biomedical settings. Ultimately this new approach to NV based quantum sensing paves the way towards minimally invasive real-time mapping and observation of free radicals in in vitro cellular environments.

Nanoscale Dynamic Readout of a Chemical Redox Process Using Radicals Coupled with Nitrogen-Vacancy Centers in Nanodiamonds

“…Recently, relaxometry has been shown useful for pH sensing, and the T 1 protocol has been enhanced to take into account ionization and recharging of the NV centers . Additionally, a similar approach for dynamic quantum sensing of paramagnetic species based on spin-dependent emission of photoluminescence was recently established . Specific detection of chemical events using T 1 relaxometry is also possible but requires a chemical or mechanochemical transducer. , …”

“…30 Additionally, a similar approach for dynamic quantum sensing of paramagnetic species based on spin-dependent emission of photoluminescence was recently established. 31 Specific detection of chemical events using T 1 relaxometry is also possible but requires a chemical 16 or mechanochemical transducer. 32,33 Chemical reactions of great scientific interest are cellular oxidation−reduction (redox) processes.…”

A Molecular Approach to Quantum Sensing

“…Current efforts have utilized entangled photons and NV centers in diamond for nanoscale and single-molecule magnetic resonance of various chemical species. 120 − 124 Single-molecule detection by quantum sensors can greatly benefit chemical separation and analysis devices. For example, merging the sensitivity of quantum sensors with microfluidic devices could enable miniaturization of devices for chemical separations and analysis on the molecular scale.…”

Nanodiamonds based optical-fiber quantum probe for magnetic field and biological sensing

“…Particularly, the NV centers have shown great potentials for the detection of the physiologically relevant species (e.g. free radicals, paramagnetic molecules, and ions) [8][9][10] and pH 11,12 , which play an essential role in various critical biological processes, in a label-free manner. For example, Y. Ninio et.al realized a high sensitivity detection to hydroxyl radical by exploiting the fluorescence difference between NV charged states 8 .…”