Single‐Particle Tracking and Trajectory Analysis of Fluorescent Nanodiamonds in Cell‐Free Environment and Live Cells

Abstract

Diamond magnetometry can provide new insights on the production of free radicals inside live cells due to its high sensitivity and spatial resolution. However, the measurements often lack intracellular context for the recorded signal. In this paper, the possible use of single‐particle tracking and trajectory analysis of fluorescent nanodiamonds (FNDs) to bridge that gap is explored. It starts with simulating a set of different possible scenarios of a particle's movement, reflecting different modes of motion, degrees of confinement, as well as shapes and sizes of that confinement. Then, the insights from the analysis of the simulated trajectories are applied to describe the movement of FNDs in glycerol solutions. It is shown that the measurements are in good agreement with the previously reported findings and that trajectory analysis yields meaningful results, when FNDs are tracked in a simple environment. Then the much more complex situation of FNDs moving inside a live cell is focused. The behavior of the particles after different incubation times is analyzed, and the possible intracellular localization of FNDs is deducted from their trajectories. Finally, this approach is combined with long‐term magnetometry methods to obtain maps of the spin relaxation dynamics (or T1) in live cells, as FNDs move through the cytosol.

Fluorescent Nanodiamonds for Tracking Single Polymer Particles in Cells and Tissues

“…Additionally, system drift could have a certain localization error, but there is not a massive impact on trajectories based on previous work. 43 To summarize, the trajectory of a particle could be affected by many factors, and cells respond to different particle shapes and sizes, which influence trajectories.…”

“…Most importantly, FNDs can host color centers that are protected within the diamond crystal lattice and emit infinitely stable fluorescence. Making use of these properties, FNDs have been utilized for long-term fluorescent labeling as well as tracking. − By attaching antibodies, glycans, or targeting peptides, it is possible to target nanodiamonds to specific regions within the cell or tissue to visualize these structures. − It is also attractive that FNDs are well visible in different imaging techniques, which are interesting for correlative microscopy . Finally, nanodiamonds can be used for quantum sensing to determine the particle orientation, temperature, , or the free radical load in their surroundings. − Here, we use these FNDs for the first time to track where polymer particles reside within cells or tissues.…”

Biocompatible Film‐Coating of Magnetic Soft Robots for Mucoadhesive Locomotion

“…T1 measurements allow local detection of the sum of all radicals within a few tens of nm from a nanodiamond particle with a mean hydrodynamic diameter of 70 nm and a flake‐like structure (Adamas Nanotechnologies, NC, USA) as probes. [ 48–52 ] They were produced by HPHT synthesis and irradiated with 3 MeV electrons at a fluence of $$5 \times {10^{19}}{\rm{e}}\;{\rm{c}}{{\rm{m}}^{ - 2}}$$ to produce nitrogen vacancy (NV) centers. As a result each particle contained ≈500 NV centers.…”

“…T1 measurements allow local detection of the sum of all radicals within a few tens of nm from a nanodiamond particle with a mean hydrodynamic diameter of 70 nm and a flakelike structure (Adamas Nanotechnologies, NC, USA) as probes. [48][49][50][51][52] They were produced by HPHT synthesis and irradiated with 3 MeV electrons at a fluence of 5 10 e cm 19 2…”

Intracellular Relaxometry, Challenges, and Future Directions

“…A different approach is to deduct the properties of the ND’s environment from the way the particles moved during the experiment. It is possible to combine single-particle tracking and trajectory analysis with T 1 measurements to get a map of T 1 values as the ND moves through the cell . This approach requires a complicated analysis of the trajectories, as NDs move in complex patterns through a highly nonuniform intracellular environment.…”