Quantum monitoring of cellular metabolic activities in single mitochondria

Abstract

Free radicals play a vital role in all kinds of biological processes including immune responses. However, free radicals have short lifetimes and are highly reactive, making them difficult to measure using current methods. Here, we demonstrate that relaxometry measurement, or T1, inherited from the field of diamond magnetometry can be used to detect free radicals in living cells with subcellular resolution. This quantum sensing technique is based on defects in diamond, which convert a magnetic signal into an optical signal, allowing nanoscale magnetic resonance measurements. We functionalized fluorescent nanodiamonds (FNDs) to target single mitochondria within macrophage cells to detect the metabolic activity. In addition, we performed measurements on single isolated mitochondria. We were able to detect free radicals generated by individual mitochondria in either living cells or isolated mitochondria after stimulation or inhibition.

Applying NV center-based quantum sensing to study intracellular free radical response upon viral infections

“…Although, the necessity of low pH for SFV fusion is discussed in the literature [ 33 , 58 ], whether SFV infection actively modifies the intracellular pH is not yet clear. However, from our previous measurements of pH versus T 1 we conclude that T 1 was not influenced by pH significantly in the relevant pH range [ 59 ].…”

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

“…), which, however, are beyond the scope of this paper and will be presented in our other work. Paramagnetic species (PS) such as free radicals and paramagnetic metalloproteins, which contain one or more unpaired electrons in their valence shell, play crucial roles in various physiological processes including tumor growth 33 , immune response 34 , and metabolism 35 , etc. Especially, increasing research suggests that endogenous PS have become the biomarkers for a variety of diseases 36, 37 .…”

Intracellular Thermal Probing Using Aggregated Fluorescent Nanodiamonds

“…More importantly, it is very difficult for such micrometer-sized solid dielectric spheres to enter a living cell via endocytosis. Thus, to obtain a given fluorescence emission intensity for the detection of multiple regions, a lower excitation power could be applied to the aggregated microspheres compared with dispersed single nanoprobes, [42][43][44][45][46] thereby reducing photodamage to the cells (Section S3.2 and Figure S12, Supporting Information).…”

“…[39][40][41] Despite being a simple and reliable way to build superstructures using low optical power, thermal conversion requires a gold film, which limits its application to single cells. Nanoparticles with chemical or protein modifications enable imaging with a high spatial resolution, [42][43][44][45][46] but their assembly and detection can only be implemented at specific locations because organelle binding is required.…”