Fluorescent nanodiamonds quantum sensing free radicals in bio-samples

Free radicals play a role in several diseases, such as Huntington’s disease (HD), Alzheimer diseases (AD). Therefore, mapping identifying and quantifying radicals can contribute to diagnose of these diseases. All the advantages of diamond particles make diamond magnetometry a promising tool in detecting magnetic noises generated by radicals.Magnetic resonance imaging (MRI) is one of the most important diagnostic techniques allowing noninvasive imaging of tissue and organs inside the body. However, the sensitivity of MRI is only sufficient to detect large defects (in the range of millimeters or micrometers at best) in tissue, which limits its applications for early diagnostic of important disease. Fluorescent nanodiamonds (FNDs) are promising to overcome these issues. NV centers within their lattice can convert magnetic noise into optical signals. They have outstanding photostability and biocompatibility. The fluorescence is extremely stable without bleaching or blinking, which allows long term tracking in living biological samples at a single particle level. These features allow measuring magnetic noise with high sensitivity at nanoscale spatial resolution. In chapter 1, a general introduction was given, describing the scientific background and research gaps. Quantum sensing of free radicals using Nitrogen-Vacancy centers (NV centers) built inside diamonds was stressed, as well as using diamond as a biosensor.To detect free radical generation, a diamond particle should be really close to the region of interest. Mitochondria are our region of interest here since they are the biggest contributors of producing radicals in most mammalian cells. In order to measure radical generation in mitochondria, diamond should be attached to the mitochondrial surface. To this end, in chapter 2, antiVDAV2 antibodies were used to coat the diamond surface to bring them to mitochondria either in cells or isolated mitochondria. By using these targeted diamond particles, radical generation of mitochondria was investigated followed by triggering or inhibiting production. T1 measurements were performed in both single cell or isolated mitochondria, similar results obtained when samples exposed to the same chemical either single cell or isolated mitochondria.Chapter 3 followed diamonds journey inside HeLa cells. In this chapter, pH sensitive, dextran coated FNDs were showed can be used to visualize the endocytosis pathway. Moreover, the coating was found significantly improved cellular uptake and the incubation time was reduced to only 30min. Nanodiamonds were further demonstrate enter Hela cells via endo-lysosome vesicles and are eventually expelled by cells.In chapter 4, diamond magnetometry was applied in human primary cells. These primary cells readily internalize diamonds. Diamonds are not toxic to cells even at high concentrations (10 µg/mL). Diamond particles were located in endo-phagosomes after 1 hour of incubation. With diamond particles inside phagosomes, superoxide radicals were generated by NADPH oxidase (NOX2) and measured by diamond magnetometry.The projects conducted in this thesis proves that diamond magnetometry is a useful tool in free radical detection