The Frontiers in Neurophotonics Symposium is a biennial event that brings together neurobiologists and physicists/engineers who share interest in the development of leading-edge photonics-based approaches to understand and manipulate the nervous system, from its individual molecular components to complex networks in the intact brain. In this Community paper, we highlight several topics that have been featured at the symposium that took place in October 2022 in Québec City, Canada.
Progress achieved in the field of stem-cell technology allows the reprogramming of patient-derived cells, obtained from urine or skin biopsies, into induced pluripotent stem cells that can then be differentiated into any cell types. Within this framework, techniques, being able to accurately and non-invasively characterize cell structure, morphology, and dynamics, represent very promising approaches to identify disease-specific cell phenotypes. Consequently, we will present how a label-free optofluidic platform, based on quantitative-phase digital holographic microscopy along with various experimental developments in microfluidics, constitutes a very appealing cell imaging methodology to identify, through the measurement of biophysical properties, specific cell phenotypes.
We have developed Polychromatic Digital Holographic Microscopy (P-DHM), providing quasi coherent noise-free OPD images, but with some limitations regarding the acquisition and reconstruction time of the multi-wavelength holograms. Our recent work, enabling a fully automated multi-wavelength hologram reconstruction associated with an increased acquisition speed, achieving a frame rate between 6 and 15 fps, while preserving OPD high sensitivity, have led to a P-DHM efficient for live-cell imaging. In addition to these technical developments, appealing applications such as the exploration of intracellular trafficking, cell migration, and neurite evolution achieved with P-DHM will be presented.
Digital holographic microscopy (DHM), provides an extremely sensitive quantitative-phase signal (QPS), which is nevertheless affected by coherent noise. The recent development of polychromatic DHM (P-DHM) enables us to provide quasi-coherent-noise-free quantitative-phase images. The implementation of P-DHM remains, however, demanding. We propose a convolutional neural network architecture, using for the first time an experimental ground-truth dataset, performing the P-DHM denoising from conventional DHM images. The results highlight, a strong efficiency, fine subcellular structures are made visible without loss of QPS accuracy, an interest in comparison to state-of-the-art learning methods and the possibility of a more widespread use of the P-DHM.
KEYWORDS: Digital holography, Holograms, Microscopy, Holography, Time lapse microscopy, Chromatic aberrations, 3D image reconstruction, Molecules, Life sciences, Imaging systems
Polychromatic digital holographic microscopy (P-DHM) has proven its capacity to provide quasi-coherent noise-free quantitative-phase images, allowing a high-quality visualization of cell structure. In this work we propose a fully automated hologram reconstruction methodology, including a fast-numerical approach for the correction of the defocusing resulting from both the axial chromatic aberrations as well as the fluctuations of the optomechanical elements. This methodology able to reconstruct a large number of holograms paves the way to develop a time-resolved P-DHM capable of non-invasively visualizing both the fine cell structure and dynamics.
We have developed a polychromatic digital holographic microscope (P-DHM) as a quasi-speckle-free quantitative-phase imaging, having preserved its nanometric sensitivity from interferometric detection, for live-cell imaging. With this approach, we can visualize tiny subcellular structures and monitor various fine cellular dynamic events including neuronal branching and connectivity rearrangement, lamellipodia movements and cellular trafficking. We are working to reach a higher frame-rate to image faster-acting cellular phenomena like neuronal excitation.
KEYWORDS: Digital holography, Microfluidics, Microscopy, Holography, Microfluidic imaging, Refractive index, Modulation, Environmental sensing, Control systems
Biophysical properties (BPs) of a cell depend drastically on its physiological or pathological state. Thus, being able to accurately and non-invasively measure a set of cell BPs, that reflect these cellular states, is of major importance. To this end, we propose an approach that combines customized fluidic devices with digital holographic microscopy (DHM). Specifically, we have developed several low-cost 3D-printed millifluidic devices which when combined with DHM allow to measure in a controlled physiological environment specific cell BPs including intracellular refractive index, absolute cell volume, membrane flickering as well as cell elasticity and viscosity moduli.
Digital holographic microscopy (DHM) has been used in numerous successful studies in materials and life sciences. It is well known that the light source coherence, useful to generate high-quality interference patterns that encode the phase in an extremely accurate manner, generates coherent noise (CN), which precludes to adequately address some important applications, especially when single-shot fast recording is required. We propose an original approach, called polychromatic DHM, which thanks to the reconstruction of several holograms acquired at different wavelengths provides quasi-CN-free optical path difference images. Preliminary results concerning materials and life sciences will be presented.
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