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Register a new userReal-time nanodiamond thermometry probing in-vivo thermogenic responses
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Real-time temperature monitoring inside living organisms provides a direct measure of their biological activities, such as homeostatic thermoregulation and energy metabolism. However, it is challenging to reduce the size of bio-compatible thermometers down to submicrometers despite their potential applications for the thermal imaging of subtissue structures with single-cell resolution. Light-emitting nanothermometers that remotely sense temperature via optical signals exhibit considerable potential in such textit{in-vivo} high-spatial-resolution thermometry. Here, using quantum nanothermometers based on optically accessible electron spins in nanodiamonds (NDs), we demonstrate textit{in-vivo} real-time temperature monitoring inside textit{Caenorhabditis elegans} (textit{C. elegans}) worms. We developed a thermometry system that can measure the temperatures of movable NDs inside live adult worms with a precision of $pm 0.22^{circ}{rm C}$. Using this system, we determined the increase in temperature based on the thermogenic responses of the worms during the chemical stimuli of mitochondrial uncouplers. Our technique demonstrates sub-micrometer localization of real-time temperature information in living animals and direct identification of their pharmacological thermogenesis. The results obtained facilitate the development of a method to probe subcellular temperature variation inside living organisms and may allow for quantification of their biological activities based on their energy expenditures.
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In this study, we analyze the operational process of nanodiamond (ND) quantum thermometry based on wide-field detection of optically detected magnetic resonance (ODMR) of nitrogen vacancy centers, and compare its performance with that of confocal ODMR detection. We found that (1) the thermometry results are significantly affected by the shape and size of the camera region of interest (ROI) surrounding the target NDs and that (2) by properly managing the ROI and acquisition parameters of the camera, a temperature precision comparable to confocal detection in living cells can be obtained by wide-field ODMR. Our results are significant to the development of camera-based real-time large-area quantum thermometry of living cells.
We investigate the real-time estimation protocols for the frequency shift of optically detected magnetic resonance (ODMR) of nitrogen-vacancy (NV) centers in nanodiamonds (NDs). Efficiently integrating multipoint ODMR measurements and ND particle tracking into fluorescence microscopy has recently demonstrated stable monitoring of the temperature inside living animals. We analyze the multipoint ODMR measurement techniques (3-, 4-, and 6-point methods) in detail and quantify the amount of measurement artifact owing to several systematic errors derived from instrumental errors of experimental hardware and ODMR spectral shape. We propose a practical approach to minimize the effect of these factors, which allows for measuring accurate temperatures of single NDs during dynamic thermal events. We also discuss integration of noise filters, data estimation protocols, and possible artifacts for further developments in real-time temperature estimation. The present study provides technical details of quantum diamond thermometry and discusses factors that may affect the temperature estimation in biological applications.
Understanding the coordination of cell division timing is one of the outstanding questions in the field of developmental biology. One active control parameter of the cell cycle duration is temperature, as it can accelerate or decelerate the rate of biochemical reactions. However, controlled experiments at the cellular-scale are challenging due to the limited availability of biocompatible temperature sensors as well as the lack of practical methods to systematically control local temperatures and cellular dynamics. Here, we demonstrate a method to probe and control the cell division timing in Caenorhabditis elegans embryos using a combination of local laser heating and nanoscale thermometry. Local infrared laser illumination produces a temperature gradient across the embryo, which is precisely measured by in-vivo nanoscale thermometry using quantum defects in nanodiamonds. These techniques enable selective, controlled acceleration of the cell divisions, even enabling an inversion of division order at the two cell stage. Our data suggest that the cell cycle timing asynchrony of the early embryonic development in C. elegans is determined independently by individual cells rather than via cell-to-cell communication. Our method can be used to control the development of multicellular organisms and to provide insights into the regulation of cell division timings as a consequence of local perturbations.
Versatile nanoscale sensors that are susceptible to changes in a variety of physical quantities often exhibit limited selectivity. We propose a novel scheme based on microwave-dressed spin states for optically probed nanoscale temperature detection using diamond quantum sensors, which provides selective sensitivity to temperature changes. By combining this scheme with a continuous pump-probe scheme using ensemble nitrogen-vacancy centers in nanodiamonds, we demonstrate a sub-100-nanosecond temporal resolution with thermal sensitivity of 3.7 K$cdot$Hz$^{-1/2}$ that is insensitive to variations in external magnetic fields on the order of 2 G. The presented results are favorable for the practical application of time-resolved nanoscale quantum sensing, where temperature imaging is required under fluctuating magnetic fields.
Dangerous damage to mitochondrial DNA (mtDNA) can be ameliorated during mammalian development through a highly debated mechanism called the mtDNA bottleneck. Uncertainty surrounding this process limits our ability to address inherited mtDNA diseases. We produce a new, physically motivated, generalisable theoretical model for mtDNA populations during development, allowing the first statistical comparison of proposed bottleneck mechanisms. Using approximate Bayesian computation and mouse data, we find most statistical support for a combination of binomial partitioning of mtDNAs at cell divisions and random mtDNA turnover, meaning that the debated exact magnitude of mtDNA copy number depletion is flexible. New experimental measurements from a wild-derived mtDNA pairing in mice confirm the theoretical predictions of this model. We analytically solve a mathematical description of this mechanism, computing probabilities of mtDNA disease onset, efficacy of clinical sampling strategies, and effects of potential dynamic interventions, thus developing a quantitative and experimentally-supported stochastic theory of the bottleneck.
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