35 research outputs found
Fluorescent nanodiamonds as free radical sensors in live mammalian cells
Free radicals are atoms and molecules that contain at least one unpaired electron. For decades, they have attracted the attention of researchers, due to their role in numerous biological processes, both in health and disease. Due to their high reactivity, however, free radicals have always been difficult to detect with high sensitivity and resolution. Nanodiamonds – diamond nanoparticles – have been used as labels due to their exceptional biocompatibility and the extremely stable fluorescence of their color centers. This fluorescence can be modulated by external factors, such as magnetic fields. This property has led to the idea of using nanodiamonds to sense the magnetic fields generated by free radicals in biological samples. This thesis explores the applications of nanodiamond-based magnetometry for free radical detection in live mammalian cells and tackles some of the challenges of this approach
Relaxometry with Nitrogen Vacancy (NV) Centers in Diamond
[Image: see text] Relaxometry is a technique which makes use of a specific crystal lattice defect in diamond, the so-called NV center. This defect consists of a nitrogen atom, which replaces a carbon atom in the diamond lattice, and an adjacent vacancy. NV centers allow converting magnetic noise into optical signals, which dramatically increases the sensitivity of the readout, allowing for nanoscale resolution. Analogously to T1 measurements in conventional magnetic resonance imaging (MRI), relaxometry allows the detection of different concentrations of paramagnetic species. However, since relaxometry allows very local measurements, the detected signals are from nanoscale voxels around the NV centers. As a result, it is possible to achieve subcellular resolutions and organelle specific measurements. A relaxometry experiment starts with polarizing the spins of NV centers in the diamond lattice, using a strong laser pulse. Afterward the laser is switched off and the NV centers are allowed to stochastically decay into the equilibrium mix of different magnetic states. The polarized configuration exhibits stronger fluorescence than the equilibrium state, allowing one to optically monitor this transition and determine its rate. This process happens faster at higher levels of magnetic noise. Alternatively, it is possible to conduct T1 relaxation measurements from the dark to the bright equilibrium by applying a microwave pulse which brings NV centers into the −1 state instead of the 0 state. One can record a spectrum of T1 at varying strengths of the applied magnetic field. This technique is called cross-relaxometry. Apart from detecting magnetic signals, responsive coatings can be applied which render T1 sensitive to other parameters as pH, temperature, or electric field. Depending on the application there are three different ways to conduct relaxometry experiments: relaxometry in moving or stationary nanodiamonds, scanning magnetometry, and relaxometry in a stationary bulk diamond with a stationary sample on top. In this Account, we present examples for various relaxometry modes as well as their advantages and limitations. Due to the simplicity and low cost of the approach, relaxometry has been implemented in many different instruments and for a wide range of applications. Herein we review the progress that has been achieved in physics, chemistry, and biology. Many articles in this field have a proof-of-principle character, and the full potential of the technology still waits to be unfolded. With this Account, we would like to stimulate discourse on the future of relaxometry
Not all cells are created equal - endosomal escape in fluorescent nanodiamonds in different cells
Successful delivery of fluorescent nanodiamonds (FNDs) into the cytoplasm is essential to many biological applications. Other applications require FNDs to stay within the endosomes. The diversity of cellular uptake of FNDs and following endosomal escape are less explored. In this article, we quantify particle uptake at a single cell level. We report that FNDs enter into the cells gradually. The number of internalized FNDs per cell differs significantly for the cell lines we investigated at the same incubation time. In HeLa cells we do not see any significant endosomal escape. We also found a wide distribution of FND endosomal escape efficiency within the same cell type. However, compared with HeLa cells, FNDs in HUVECs can easily escape from the endosomes and less than 25% FNDs remained in the vesicles after 4 h incubation time. We believe this work can bring more attention to the diversity of the cells and provide potential guidelines for future studies
Fluorescent Nanodiamonds for Detecting Free-Radical Generation in Real Time during Shear Stress in Human Umbilical Vein Endothelial Cells
Free-radical generation is suspected to play a key role in cardiovascular diseases. Another crucial factor is shear stress. Human umbilical vein endothelial cells (HUVECS), which form the lining of blood vessels, require a physiological shear stress to activate many vasoactive factors. These are needed for maintaining vascular cell functions such as nonthrombogenicity, regulation of blood flow, and vascular tone. Additionally, blood clots form at regions of high shear stress within a blood vessel. Here, we use a new method called diamond magnetometry which allows us to measure the dynamics of free-radical generation in real time under shear stress. This quantum sensing technique allows free-radical detection with nanoscale resolution at the single-cell level. We investigate radical formation in HUVECs in a microfluidic environment under different flow conditions typically found in veins and arteries. Here, we looked into free-radical formation before, during, and after flow. We found that the free-radical production varied depending on the flow conditions. To confirm the magnetometry results and to differentiate between radicals, we performed conventional fluorescent reactive oxygen species (ROS) assays specific for superoxide, nitric oxide, and overall ROS
Targeting Nanodiamonds to the Nucleus in Yeast Cells
Nanodiamonds are widely used for drug delivery, labelling or nanoscale sensing. For all these applications it is highly beneficial to have control over the intracellular location of the particles. For the first time, we have achieved targeting the nucleus of yeast cells. In terms of particle uptake, these cells are challenging due to their rigid cell wall. Thus, we used a spheroplasting protocol to remove the cell wall prior to uptake. To achieve nuclear targeting we used nanodiamonds, which were attached to antibodies. When using non-targeted particles, only 20% end up at the nucleus. In comparison, by using diamonds linked to antibodies, 70% of the diamond particles reach the nucleus
Fluorescent Nanodiamonds for Tracking Single Polymer Particles in Cells and Tissues
Polymer nanoparticles are widely used in drug delivery and are also a potential concern due to the increased burden of nano- or microplastics in the environment. In order to use polymer nanoparticles safely and understand their mechanism of action, it is useful to know where within cells and tissues they end up. To this end, we labeled polymer nanoparticles with nanodiamond particles. More specifically, we have embedded nanodiamond particles in the polymer particles and characterized the composites. Compared to conventional fluorescent dyes, these labels have the advantage that nanodiamonds do not bleach or blink, thus allowing long-term imaging and tracking of polymer particles. We have demonstrated this principle both in cells and entire liver tissues.</p
The fate of lipid-coated and uncoated fluorescent nanodiamonds during cell division in yeast
Fluorescent nanodiamonds are frequently used as biolabels. They have also recently been established for magnetic resonance and temperature sensing at the nanoscale level. To properly use them in cell biology, we first have to understand their intracellular fate. Here, we investigated, for the first time, what happens to diamond particles during and after cell division in yeast (Saccharomyces cerevisiae) cells. More concretely, our goal was to answer the question of whether nanodiamonds remain in the mother cells or end up in the daughter cells. Yeast cells are widely used as a model organism in aging and biotechnology research, and they are particularly interesting because their asymmetric cell division leads to morphologically different mother and daughter cells. Although yeast cells have a mechanism to prevent potentially harmful substances from entering the daughter cells, we found an increased number of diamond particles in daughter cells. Additionally, we found substantial excretion of particles, which has not been reported for mammalian cells. We also investigated what types of movement diamond particles undergo in the cells. Finally, we also compared bare nanodiamonds with lipid-coated diamonds, and there were no significant differences in respect to either movement or intracellular fate
Quantum monitoring the metabolism of individual yeast mutant strain cells when aged, stressed or treated with antioxidant
Free radicals play a key role in the ageing process. The strongly debated
free radical theory of ageing even states that damage caused by free radicals
is the main cause of aging on a cellular level. However, free radicals are
small, reactive and short lived and thus challenging to measure. We utilize a
new technique called diamond magnetometry for this purpose. We make use of
nitrogen vacancy centers in nanodiamonds. Via a quantum effect these defects
convert a magnetic resonance signal into an optical signal. While this method
is increasingly popular for its unprecedented sensitivity in physics, we use
this technique here for the first time to measure free radicals in living
cells. Our signals are equivalent to T1 signals in conventional MRI but from
nanoscale voxels from single cells with sub-cellular resolution. With this
powerful tool we are able to follow free radical generation after chemically
inducing stress. In addition, we can observe free radical reduction in presence
of an antioxidant. We were able to clearly differentiate between mutant strains
with altered metabolism. Finally, the excellent stability of our diamond
particles allowed us to follow the ageing process and differentiate between
young and old cells. We could confirm the expected increase of free radical
load in old wild type and sod1{\Delta} mutants. We further applied this new
technique to investigate tor1{\Delta} and pex19{\Delta} cells. For these
mutants an increased lifespan has been reported but the exact mechanism is
unclear. We find a decreased free radical load in, which might offer an
explanation for the increased lifespan in these cells.Comment: Main Text: 21 pages, 4 figures / Supplementary information: 13 pages,
13 figure