MEGA-FLIM: quantum technologies for megapixel time-resolved imaging and control across biological scales

Lead Research Organisation: University of Glasgow
Department Name: College of Medical, Veterinary, Life Sci

Abstract

Embryos, organs and tumours are composed of many cells, which interact with each other and communicate across distances of several cells. While it is routine to study single cells under a microscope, it is much more difficult to study collectives due to their size, light scattering properties and complexity. Fluorescence lifetime imaging (FLIM) and FRET (Forster resonance energy transfer) use the principles of energy transfer that occur when a light particle (photon) jumps from an excited fluorescent donor molecule to a nearby acceptor, thus changing the fluorescence lifetime of the donor. FLIM is used to measure close molecular interactions inside of living cells by measuring this lifetime change. We will combine physics, engineering, computation and biology to build a new light microscopic system, with extremely high spatial and temporal resolution. We call our system MEGA-FLIM and we will use it to study larger cell collectives of cells to discover how cells communicate and organise in response to both mechanical and chemical signals. MEGA-FLIM will allow much faster collection of light signals across a much larger field than previously possible. We will also develop technology to use light to control cell behaviour across these collectives using the technique called optogenetics. Our unique team of optical physicists, bioengineers and biologists is ideally placed to break down current barriers, leading to landmark discovery in each of these fields.

Why do we need a new FLIM microscope system?
Commercial systems are lacking that allow, simultaneously:
- fast acquisition (0.1 second or faster) so as to allow real-time measurements in live cells or embryos
- across a widefield area with high resolution (1 million pixels or higher), so as to allow imaging of the full cell environment and large collectives
- with high time resolution (50-100 pico seconds), so as to allow precise discrimination of lifetimes
- two-photon excitation, so as to allow precise full 3D reconstruction of cell collectives.
- widefield optogenetic activation (light-controlled cell behaviour), so as to allow study of the dynamics of collectives in the presence of complex activation stimuli that act across multiple sites.

What problems will this new system solve and what impact will it have?
-MEGA FLIM will provide a system that will allow us to interrogate living systems at molecular resolution and discover how cells collectively signal using both chemical and mechanical signals to steer when they migrate. This kind of steering allows cells to recognise each other and other cell types and to form complex patterns in 3 dimensions (like in an organ or an embryo).
-Our new system will be of great commercial interest, as it will advance capabilities in imaging and optogenetic control of cell behaviour with light.
-By building a system whereby we can discover new pathways governing how cells behave in collectives, we will gain the ability to reliably and predictably control collective cell behaviour. This discipline, known as synthetic biology, is highly desirable for medical and commercial use in building organ/tumour-on-chip systems or creating physiologically relevant systems to use in drug discovery.

Planned Impact

Embryos, organs and tumours are composed of many cells, which interact with each other and communicate across distances of several cells. While it is routine to study single cells under a microscope, it is much more difficult to study collectives due to their size, light scattering properties and complexity. Fluorescence lifetime imaging (FLIM) and FRET (Forster resonance energy transfer) use the principles of energy transfer that occur when a photon jumps from an excited fluorescent donor molecule to a nearby acceptor, thus changing the fluorescence lifetime of the donor. It is used to measure close molecular interactions inside of living cells by measuring the lifetime change. We will combine physics, engineering, computation and biology to build a new light microscopic system, with extremely high spatial and temporal resolution. We call our system MEGA-FLIM and we propose to use it to study larger cell collectives and discover how cells communicate and organise in response to both mechanical and chemical signals. MEGA-FLIM will allow much faster collection of light signals across a much larger field than previously possible. We will also develop technology to use light to control cell behaviour across these collectives using the technique of optogenetics. Our unique team of optical physicists, bioengineers and biologists is ideally placed to break down current barriers, leading to landmark discovery in each of these fields.

Why do we need a new FLIM system?
Commercial systems are lacking that allow, simultaneously:
- fast acquisition (0.1 second or faster) so as to allow real-time measurements in vivo
- across a widefield area with high resolution (1 Mpixel or higher), so as to allow imaging of the full cell environment and large collectives
- with high temporal resolution (50-100 ps), so as to allow precise discrimination of lifetimes
- two-photon excitation, so as to allow precise full 3D reconstruction of cell collectives.
- widefield optogenetic activation, so as to allow to study the dynamics of collectives in the presence of complex activation stimuli that act across multiple sites.

What problems will this new system solve and what impact will it have?
-MEGA FLIM will provide a system that will allow us to interrogate live and at molecular resolution for the first time how cells collectively signal using adhesion/mechanical sensing, G-proteins and chemical signals to steer when they migrate, to recognise each other and other cell types and to form complex patterns in 3 dimensions (like in an organ or an embryo).
-Our new system will be of great commercial interest, as it will advance capabilities in imaging and optogenetic control of cell behaviour with light.
-By building a system whereby we can discover new pathways governing how cells behave in collectives, we will gain the ability to reliably and predictably control collective cell behaviour. This discipline, known as synthetic biology, is highly desirable for medical and commercial use in building organ/tumour-on-chip systems or creating physiologically relevant systems to use in drug discovery.
-We will gain significant knowledge both in optical physics and collective cell behaviour that will impact on basic research into how organs/organisms and tumours form.

Publications

10 25 50
 
Description Most significant findings:
Our original objectives were as follows:
A1. Develop and employ computational data fusion for megapixel time-resolved imaging
A2. Develop 2-photon, light-sheet microscopy for high speed megapixel FLIM imaging
A3. Develop advanced light shaping for optogenetic control
A4. MEGA-FLIM to study 3D and collective cell behaviour

We have achieved Aim 1, using fusion of data obtained from high spatial resolution CMOS camera with the data obtained from a SPAD camera with high temporal resolution. We have successfully developed this technology to image cells expression genetically encoded FLIM biosensors for RAC1. One major challenge has been to obtain enough signal from our genetically encoded probes to work with the system. However, we were able to obtain a good fit for our FLIM data from cancer cells expressing the RAC1 probe, indicating that our imaging approach was successful. This study was published in Callenberg et al., Sci Rep. 11(1) 2021.

We have achieved Aim2 and are currently installing the light sheet microscope into the Beatson Institute. This part of the project was severely delayed by the covid-19 pandemic, which prevented the physics and biology teams from working together. However, we are now confident that we will have this microscope collecting data soon.

We have not achieved Aim 3 of optogenetic light shaping, because it was no longer practical in the short time frame of this project, given that 2 years of the project were impacted by the covid19 pandemic.

For aim 4, we are continuing to develop both the physics and the biology aspects of the project to innovate new ways to combine novel breakthroughs in fluorescence imaging. An example is our work with Dr Ashley Lyons, an associate member of the MEGA-FLIM team. He and Faccio have developed a very interesting opportunity for utilising a quantum interference effect that promises a route to measuring extremely short lifetimes (picoseconds or less) with extremely low photon fluxes. The team have developed a fundamentally new method for measuring lifetimes which uses optical intensity interference rather than relying on timing electronics. This allows the resolution to be increased by at least 2 orders of magnitude, limited only by the bandwidth of the laser pulse. The basic principle utilises "Hong-Ou-Mandel" or "Two-Photon" interference whereby two identical photons that meet at a beamsplitter will preferentially bunch together and leave via the same output port. This can be evaluated by measuring correlations between two detectors at either beamsplitter output whilst changing the arrival time of one of the photons, which acts as a reference. When the two photons overlap at the beamsplitter at the same time, a characteristic dip is seen in the second order correlation function, g(2), due to this bunching effect. Ongoing work will combine this new method of lifetime sensing with our previous work on imaging with two-photon interference, resulting in a wide-field picosecond resolution FLIM system. This forms the basis of Dr Lyons' recently awarded Leverhulme Trust Early Career Fellowship, demonstrating how our project has helped foster the careers of our ECRs. The group led by Prof Machesky are continuing to support the fellowship by providing cancerous cell samples and by advising on the most crucial applications in cancer research including autofluorescent signals which have lifetimes too short to address with current techniques. These results are literally fresh out of the lab as we write. So we will also be working with the whole team in the next months to discuss the opportunities of this technique and also assess in detail its actual utility for bio-imaging.

Taking the findings forward:
We are continuing to develop the MEGA-FLIM light sheet microscope and to optimise probes that can allow us to image cell collectives in 3d on this system using the high spatial and temporal resolution data fusion methods. This will no doubt result in future bids for collaborative funding to continue this project and develop the FLIM methods and the biological investigations into how cancer cell collectives signal across the scales. We are also actively pursuing our novel FLIM method with Dr Ash Lyons, toward harnessing autofluorescent signals and other short-lived signals to perform FLIM imaging.

We have also made a new connection with clinicians in Edinburgh and Glasgow who are imaging mesothelioma using FLIM. We are really excited to work with them and apply some of our new methods developed with the MEGA-FLIM initiative toward helping to improve imaging toward new therapies for cancer patients.
Exploitation Route We have published the main advances in FLIM imaging made during the award, so others will be able to access the information for how to further develop our advances. We envisage that our new technology and the knowledge developed so far during this project will be useful for design of new types of imaging microscopes and advances in both basic science and medical imaging of cancer and other diseases.
Sectors Healthcare,Manufacturing, including Industrial Biotechology

 
Description One of the PI's in our group has started a collaboration with Horiba, who were partners on the grant. This has led to Horiba funding further research in his group and a continuing collaboration.
First Year Of Impact 2019
Sector Pharmaceuticals and Medical Biotechnology
Impact Types Economic

 
Description Mechanosensing, cytoskeletal control and metabolic demand: how tumour growth and metastasis is fuelled by the microenvironment
Amount £1,983,921 (GBP)
Funding ID DRCRPG-Nov22/100017 
Organisation Cancer Research UK 
Sector Charity/Non Profit
Country United Kingdom
Start 03/2023 
End 02/2028
 
Description Quantum-enabled nano-scale rheology of the microbial seawater environment
Amount £319,609 (GBP)
Funding ID EP/X035905/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Public
Country United Kingdom
Start 02/2023 
End 02/2025
 
Title Ground Truth Dataset for time resolved FLIM 
Description We have created a dataset of over 1000 images to serve as ground truth to train machine learning algorithms for FLIM image analysis. We are further developing this dataset and using it to train our systems. We plan to make it available to the public as soon as we publish the first paper describing it. 
Type Of Material Model of mechanisms or symptoms - in vitro 
Year Produced 2020 
Provided To Others? No  
Impact This tool is impacting our ability to develop new machine learning algorithms for FLIM image analysis. We predict that it will become useful to other groups and even to industry when we make it publicly available. 
 
Title CYRI-B mediated macropinocytosis drives metastasis via lysophosphatidic acid receptor uptake 
Description This dataset contains primary data in the form of images, spreadsheets for analysis and videos that support the above paper. Please see details in the readme file and use the 'Request Data' button to be sent a link to download the dataset. 
Type Of Material Database/Collection of data 
Year Produced 2022 
Provided To Others? Yes  
URL http://researchdata.gla.ac.uk/id/eprint/1371
 
Title Fluorescence lifetime imaging with a megapixel SPAD camera and neural network lifetime estimation 
Description This record contains the raw data underpinning the assoicated data, and the code required to process it. 
Type Of Material Database/Collection of data 
Year Produced 2020 
Provided To Others? Yes  
URL http://researchdata.gla.ac.uk/id/eprint/1012
 
Description Collaboration with E Charbon 
Organisation Swiss Federal Institute of Technology in Lausanne (EPFL)
Country Switzerland 
Sector Public 
PI Contribution The Mega-FLIM team in Glasgow demonstrated application of the largest time-gated SPAD array for fluorescence lifetime imaging of biologically relevant samples. We successfully applied technology developed both in Glasgow and by our partner Charbon in Switzerland to show that FLIM imaging of cancer cells could be performed using mega-pixel imaging at the extremely rapid speed of 1Hz. We also applied machine learning methods to shorten the time of data processing, to make this rapid imaging possible. We have thus pushed the boundaries of what was possible by combining novel physics with cutting edge biology.
Collaborator Contribution The Swiss team, led by Charbon, designed the SPAD camera used for this Mega-pixel imaging. Thus, by combining the technology that this team developed, with the technology and applications that we have developed for FLIM, together we pushed back a new scientific frontier.
Impact We have a publication resulting from this collaboration, which is listed as an output for this award. This is Zyckus et al., 2020 DOI: 10.1038/s41598-020-77737-0 .
Start Year 2019