Redox reactions play a fundamental role in maintaining metabolic and other processes in living cells. For a better understanding of these processes, researchers are working to develop various nanoprobes for use directly within cells. Of particular interest are sensors that can detect the magnetic properties of various particles and molecules and the processes associated with their (bio)chemical transformations.
In a study published in ACS Nano, Petr Cígler, Jan Bartoň, and researchers from IOCB Prague, Hasselt University, Ulm University, Czech Technical University in Prague, and Charles University describe a nanoprobe based on quantum sensing techniques. The researchers used optical sensing of changes in fluorescence originating in changes in the quantum states of diamond nanocrystals (nanodiamonds).
They coupled so-called nitrogen-vacancy centers inside nanodiamonds with molecules carrying stable spin in the form of an unpaired electron – a radical. These molecules, nitroxides, exhibit unusual magnetic behavior, and their magnetic communication with the nitrogen-vacancy centers inside the diamonds manifested as a change in the optical properties of the centers. Thus, it was possible to optically measure the concentration of nitroxide on the diamond particles with a high spatiotemporal resolution. The researchers also traced changes in this concentration, which are caused by chemical reactions of the nitroxides. The developed probes achieved a sensitivity of several dozen nitroxide molecules per particle (i.e. approx. 10–23–10–22 mol), which significantly expanded the boundaries of previously existing methods.
At the same time, the researchers demonstrated that a system containing diamond, nitroxides, and a specially engineered stabilizing polymer can be used dynamically for selective tracing of biologically important redox chemical processes, such as oxidation of ascorbic acid. The prepared nanoparticles thus represent the first generation of nanoprobes used for quantum detection of chemical processes in a physiological environment.
Original article: Barton, J.; Gulka, M.; Tarabek, J.; Mindarava, Y.; Wang, Z.; Schimer, J.; Raabova, H.; Bednar, J.; Plenio, M. B.; Jelezko, F.; Nesladek, M.; Cigler, P. Nanoscale Dynamic Readout of a Chemical Redox Process Using Radicals Coupled with Nitrogen-Vacancy Centers in Nanodiamonds. ACS Nano 2020. https://doi.org/10.1021/acsnano.0c04010
