Background – In the current era of images, integrated reconfigurable optical elements are essential building blocks to improve the performance of new photonic devices, all the way from the consumer market, with displays and cameras, to the research and clinic environments with advanced microscopy. To respond to new demands, several technological solutions have been proposed, including tuneable lenses, spatial light modulators and reconfigurable metasurfaces, involving a variety of actuation mechanisms. However, to date, wavefront shaping technologies do not meet the needs of many emerging photonics applications, including displays and advanced imaging, which require a combination of compacity, cost-efficiency, operation in transmission mode, and reconfigurability beyond simple refocusing. Rationale – The PROFIT project leverages on a concept recently introduced by the proposers, in which the phase of the transmitted light is shaped by using the thermo-optical effect, i.e. the temperature dependence of the refractive index of most dielectric materials (physical effect involved in mirages). By engineering the tempera-ture landscape in a thermo-optical material, one forms a distribution of refractive index associated to a desired optical element (coined as Smartlens). In a recent collaboration (Berto et al, Nature Photonics, 2019), the proposers have demonstrated the feasibility of the Smartlens approach and started exploring its potential in the context of free-form planar optics. Despite its great promises, the Smartlens concept is still in its infancy, with several limitations that currently prevent its application to advanced imaging. Overall objectives & specific aims – The PROFIT project aims at addressing these scientific and technological challenges and applying the developed technology in the contexts of endoscopy and microscopy. The first aim of the project is to enhance the performance of an individual Smartlens by increasing its transmittivity, its dynamic range and, beyond tunability, to demonstrate reconfigurability, i.e. the possibility to change optical function. The second aim is to extend operation to an ensemble of Smartlenses by combining thermal management and new optical architectures. Finally, our third aim is to demonstrate that, among its various potential applications, the developed technique can provide powerful, yet simple, solutions to the problems of in-depth and high-speed imaging, which are crucial to the progress of the currently thriving field of neurophotonics. Expected results – By combining their complementary expertises, the proposers bring together all the knowhow and skills, from photonic engineering, heat management to advanced imaging and neurophotonics, necessary to design, implement and apply the creative solutions proposed in PROFIT. Beyond advanced endoscopy and microscopy which we address here, the outcomes of the project are foreseen to impact all fields of photonics, and benefit a broad range of applications, either for scientific (e.g. adaptive optics) or consumer (e.g. cell-phone imaging, displays) systems.

Inherited retinal dystrophies (IRD) -including Retinitis Pigmentosa (RP) - that cause definitive loss of photoreceptors (PRs), typically result in permanent visual impairment. Preventing and rescuing the degenerated retina is a major challenge for which a novel pharmacotherapy based on drug discovery using patient induced pluripotent stem cell (iPSC)-based cell models could propose new treatment for IRD. We are ambitioning to use patient-derived iPSCs carrying mutation on RHODOPSIN or NR2E3 genes to create advanced cell-based models mimicking photoreceptor degenerative profile observed in RP and usable for drug and target discovery. Part of this challenge is the production of large number of identical cells behaving in the same way. To achieve this, we will develop adherent high enriched cultures of PRs from multipotent and storable human iPS-derived retinal progenitors. To find the best culture condition allowing the differentiation of progenitors to PR precursors, a high content screening test will be developed using a PR-specific fluorescent reporter iPSC line to follow PR differentiation efficiency. Based on the recapitulation of the degenerative profile of patient-derived PRs in 384-well microplates, the aim of RETINIT-iPS project is to identify cytoprotective and potential therapeutic drugs within two well annotated compound libraries representing 6479 bioactive compounds by the development high throughput cell viability assay. Then, to better understand mechanisms underlying RP pathogenicity and find new targets, an original selection funnel process, comparing transcriptomic profile of healthy and drug-treated RP cell-based models will be used to highlight drug mode of action or to identify new genes linked to the rescued phenotype. The iPSC models reported in RETINIT-iPS project represent an unhoped occasion to elaborate powerful research tool for drug development while supporting innovation and facilitating R&D and should accelerate the availability of approved drugs by repositioning prescription and start the identification of new actors for the development of innovative pharmacological treatments against RP.

Electrochemiluminescence (ECL) is the light emitted by the excited state of a luminophore upon an initial electrochemical reaction. It is a hybrid technique combining orthogonal modalities, in which electrochemical stimulation is coupled to optical detection. ECL is a powerful analytical technique, which is already appealing for medical diagnosis and, increasingly, for imaging. Our proposal aims to combine ECL with superlocalization microscopy for the 3D tracking of individual electrochemical or biological objects, and ultimately single molecules. We propose an original methodology to investigate the behavior of single entities in electrochemistry and biology using a nanometer-range precision optical readout, with all the advantages of a photoexcitation-free approach. In a first part, we will study the ECL mechanisms in order to improve the control of the reactivity of the process and tune the spatial distribution of the ECL-emitting layer in the vicinity of the electrode surface. This mechanistic insight, combined to optimized resonance energy transfer processes and the complete toolbox of molecular biology, will lead to an enhancement of ECL emission, thus allowing the ECL visualization of specific cell organelles. The development of original optical amplitude-and-phase imaging technique will enable the study of single nano-objects, biological entities and ECL-emitting molecules with unprecedented precision. The partners of the ELISE project gather complementary knowledge and recognized expertise in ECL, electrochemistry, mechanistic simulations, nano-imaging, molecular biology, and microbiology.

Our most cherished sense, vision, begins with the process of phototransduction, a process performed by the highly specialized photoreceptor cells of the retina. Seven transmembrane proteins are responsible for light capture and they have evolved into many different forms through evolution. In majority of inherited blinding diseases photoreceptor cells are altered losing the ability to capture light. To re-animate retinas that have lost their endogenous opsins it has been suggested that simple one-component invertebrate opsins can be expressed in these ‘dormant’ photoreceptors. This has lead to elegant proof-of-concept studies in rodents showing that it is possible to restore visual function. However, the major drawback with these microbial opsin systems is their low light sensitivity and difficulty of their expression in higher primates. Here, we propose to use vertebrate opsin systems specifically designed to work in remaining retinal neurons in rod-cone dystrophies. These vertebrate opsins will circumvent the shortcomings associated with one-component microbial opsins, and offer a highly therapeutically relevant solution to blindness, applicable in the clinic.

The natural visual environments in which we have evolved have shaped and constrained the neural mechanisms of vision. Rapid progress has been made in recent years in understanding how the retina and visual cortex are specifically adapted to processing natural scenes. However, studies in this research tradition have mainly addressed the processing of natural images in the spatial domain. Although the processing of temporal properties of visual stimuli is just as important as spatial properties, stimuli with naturalistically valid temporal dynamics have not been sufficiently investigated. Although objects and creatures we view undergo a variety of intrinsic movements, probably the most common motions on the retina are image shifts due to our own eye movements: in free viewing in humans, ocular saccades occur about three times every second, shifting the retinal image at speeds of 100-500 degrees of visual angle per second.4 How these very fast shifts are suppressed, leading to clear, accurate and stable representations of the visual scene is an fundamental unsolved problem in visual neuroscience known as saccadic suppression. One reason why this problem is difficult is technological: to make progress we need to visually simulate these fast retinal shifts, but computer displays have been too slow to produce adequate simulations. In this project we propose a unique convergence between neurophysiology, modeling and psychophysics, aided by recent technological developments. Some of the partners have been at the forefront of recent developments that have led to a realization that moving stimuli lead to traveling waves of activity in primary visual cortex, propagating at speeds similar to those produced by saccades. Other partners have developed detailed models of the retina and primary visual cortex based on multielectrode recordings from the retina and optical imaging of the cortex that have been able to account for these wave phenomena. Finally, another partner recently made psychophysical observations--aided by new, ultrafast computer displays that allow us to realistically simulate saccadic dynamics on a static retina--that show how image dynamics alone can account for saccadic suppression phenomena. The main hypothesis that we will be testing in this project is that cortical waves, driven by horizontal connections, are the physiological substrate behind these suppression phenomena. If this hypothesis is true, we will have solved the age-old problem of how vision is stable despite eye movements, invoking an elegant and well-documented physiological mechanisms. We expect that the convergence of these three research currents and methodologies will lead to rapid progress in understanding how the visual system is adapted to naturalistic dynamics. The psychophysical observations will provide new leads and targets for the neurophysiology and modeling, which in turn may provide detailed neural explanations for the psychophysics. We predict that the neural architectures that have been uncovered in the retina and the primary visual cortex will be revealed as most effective when processing naturalistic, fast stimuli that arise as the consequence of eye movements.