Quantum Sensing Of Mitochondrial Function

Mitochondria are small bacteria like organelles contained inside everybody's cells. Often called the battery pack of a cell, they are responsible for taking the oxygen we breathe and using it to generate a molecule known as ATP, the unit of currency for energy production inside most living organisms. Mitochondria generate ATP using chemical reactions that push protons to one side of a small membrane inside the mitochondria. This generates an imbalance of electrical charge across the membrane called mitochondrial membrane potential (MMP), equivalent in strength to the electrical field required for a bolt of lightning to strike during a thunderstorm. This charge imbalance inside the mitochondria pushes protons back through a small protein motor on the membrane to generate ATP, giving cells the energy required to function in their day-to-day tasks. The importance of this little organelle should not be understated and it is widely held to have underpinned the evolution of all complex life on earth. Dysfunctional mitochondria can cause many problems for health and have been linked to a range of diseases such as Parkinson's, heart disease, cancer and obesity.
A by-product of this energy creating process in mitochondria are molecules called free radicals. The presence of free radicals inside the body are commonly thought to be a bad thing. It is true that in some circumstances they cause damage to the body however, these free radicals are also involved in many different processes in the body that are vital for the maintenance of health. As such free radicals have to be carefully regulated such that they are not being produced at harmful levels, but in sufficient amounts to allow cells to function normally. Collectively, this balance of free radical production and MMP is referred to as the mitochondrial redox state. This redox state can be a very good indicator of whether a cell is healthy or is undergoing stress or dysfunction. For example, a hallmark of many cancers is 'the Warburg effect' in which cancer cells have a very different mechanism for generating energy which implies a change in the function of mitochondria in growing tumours. Researchers have long been interested in how to better understand mitochondria. However, the technologies we use today have certain limitations; one example is the toxic side effects of different chemicals and invasive probes used to measure MMP.
In this work we will develop a new technology that can non-destructively study mitochondria more accurately than existing methods to increase our understanding of these organelles and help develop treatments for diseases more effectively. Our approach is based on a peculiar property of pink diamond that will allow us to use a light microscope to study MMP and free radical production in living cells. Pink diamonds obtain their pinkness due to the presence of Nitrogen impurities lodged in the diamond's usually pure carbon structure. These impurities absorb green light and re-emit red/pink light. Physicists have discovered in the last 10 years that the intensity of this light can be used to measure electromagnetic fields very accurately (~250,000 times smaller than the electric field present in mitochondria) and at very short length scales (about 1 million times smaller than the width of a human hair). Our proposed work involves patterning very thin slabs of diamond with a uniform surface layer of these impurities. Then using a series of controlled pulses of green light, we can take pictures of the red/pink fluorescence using a camera and reconstruct a spatial heat map of electric fields and free radicals produced by mitochondria in cells growing on the diamond surface. We predict this new technology could overcome many of the disadvantages of currently used techniques, and will be able to provide new information about how mitochondria work. This could then lead to new and effective treatments for different diseases for the benefit of all.

Mitochondria (Mt) are small double walled membrane organelles found in all eukaryotic organisms and are vital for cell survival. Dysfunction of Mt underlies numerous diseases, predominantly those involving cells that have the highest energy demands (e.g. brain, heart, muscle). Our ability however for measurement of Mt function in living biological models at sufficient resolution and sensitivity is lacking. Here a visionary approach to Mt characterisation with single organelle sensitivity, nanoscale spatial resolution and millisecond measurement speed is proposed. This approach will exploit a major advance in fundamental physical science, namely atomic scale quantum sensors based on Nitrogen Vacancy (NV) colour defects in diamond. Central to this work is the hypothesis that the quantum spin dependant optical properties of NV defects can be harnessed to spatially and temporally study electromagnetic fields generated across the Mt membrane and reactive oxygen species (ROS) produced by Mt. The experimental program will combine state of the art advances in nanoscale surface structuring, quantum sensing protocols and optical engineering to develop a technology for non-destructive characterisation of Mt with unprecedented sensitivity. The proposed instrument will be tested and validated to assess its capability for quantum sensing in a controlled biological environment. A further advance will be the implementation of quantum bio-imaging at length scales below the optical diffraction limit using structured illumination microscopy. Following instrument testing and validation, studies of exemplar biological systems will be carried out. Mt extracted from cells and within cells will be characterised and findings compared with current state of the art Mt functional assays. This technology is projected to underpin a transformative step change in measurement capabilities in the life science.

The expected beneficiaries of the proposed quantum sensing technology are detailed below.

Healthcare sector: Dysfunction of Mt underlies numerous diseases, predominantly those involving cells that have the highest energy demands (e.g. brain, heart, muscle). The spectrum of disease types is broad including inherited disorders (e.g. mitochondrial syndrome), metastatic cancers, acute conditions (e.g. cardiovascular disease) and chronic conditions (e.g. neurodegenerative). There is currently no cure for many of these diseases and whilst the past decade has seen major advances in the understanding disease genetic basis and pathology, these findings are yet to translate to new therapies. Deployment of the proposed enabling technology to study Mt function and dysfunction with unprecedented sensitivity and resolution will deliver new and complementary information to accelerate the pace towards effective treatments and support the identification of translatable biomarkers of disease progression. The successful application of the proposed quantum sensor in the life sciences will deliver benefit to patients through the provision of new therapies and economic benefit by reducing the burden of disease on an overstretched healthcare sector.

Pharmaceutical industry: Drug induced perturbation of Mt function is recognised as a contributing factor to the late stage attrition of several pharmaceuticals. Driven by the enormous costs associated with late stage failure, pharmaceutical companies are developing in vitro cellular models for detection of drug induced Mt dysfunction early in the development pipeline. Correspondingly, there is a demand for assays capable of characterising Mt function in intact cells to enable drug testing in an environment that aims at recapitulating the complex state of internal cellular signalling interactions found in vivo. The pharmaceutical industry also stands to benefit from the availability of Mt functional assays in intact cells capable of facilitating the identification and validation of new molecular drug targets. Such assays will also support the development of drugs that prevent the downstream damage associated with diseases, particularly in the case of mitochondrial syndrome where drugs could be designed to block for example cardiovascular damage. Overall it is anticipated that deployment of the proposed technology to assay Mt function in a manner accessible to the pharmaceutical industry will have significant impact on the development and manufacture of medicines that will not only create better outcomes for patients but will drive economic growth in the pharmaceutical industry.

Quantum technology: Entirely new industries are emerging due to the advent of quantum technologies. Quantum sensing achieve unprecedented sensitivity, accuracy and resolution in measurement by coherently manipulating quantum objects. In the context of this work, the quantum object is the unpaired electron associated with the NV centre in diamond which can be exploited as an extraordinarily sensitive room temperature magnetometer, deployed for nanoscale temperature measurements and in the near future play a major role in the semiconductor industry. Indeed, quantum sensors are expected to have a significant economic impact in the coming years in a number of sectors, including health care, defence and encrypted quantum communication networks. Government projections in 2015 cite the use of quantum diamond sensors for medical diagnostics as an integral part of the developing quantum imaging sector, projected to be worth £33B globally by 2020. This economic incentive, coupled with the opportunity to understand biological systems at an entirely new and fundamental level will no doubt have a significant contribution to the future development of the rapidly advancing field of quantum technologies and help identify routes for commercial deployment of a new set of products from medical devices to sensors and safer communication.