Mesoscopic oblique plane microscopy with a diffractive light-sheet for large-scale 4D cellular resolution imaging

Mesoscopic axially swept oblique plane microscope for the imaging of freely moving organisms with near-isotropic resolution

Rapid three-dimensional imaging over extended fields of view (FOVs) is crucial to the study of organism-wide systems and biological processes in vivo. Selective-plane illumination microscopy (SPIM) is a powerful method for high spatio-temporal resolution in toto imaging of such biological specimens. However, typical SPIM implementations preclude conventional sample mounting and have anisotropic imaging performance, in particular when designed for large FOVs over 1 mm diameter. Here, we introduce axial sweeping of the illumination into a non-orthogonal dual-objective oblique plane microscope (OPM) design, thereby enabling the observation of freely moving animals over millimeter-sized FOVs, at close to isotropic, sub-cellular resolution. We apply our mesoscopic axially swept OPM (MASOPM) to image the behavioral dynamics of the sea anemone Nematostella vectensis over 1 × 0.7 × 0.4 mm at 1.7 × 2.6 × 3.7 µm resolution and 0.5 Hz volume rate.

Mesoscopic Oblique Plane Microscopy via Light-sheet Mirroring

Understanding the intricate interplay and inter-connectivity of biological processes across an entire organism is important in various fields of biology, including cardiovascular research, neuroscience, and developmental biology. Here, we present a mesoscopic oblique plane microscope (OPM) that enables whole organism imaging with high speed and subcellular resolution. A microprism underneath the sample enhances the axial resolution and optical sectioning through total internal reflection of the light-sheet. Through rapid refocusing of the light-sheet, the imaging depth is extended up to threefold while keeping the axial resolution constant. Using low magnification objectives with a large field of view, we realize mesoscopic imaging over a volume of 3.7×1.5×1 mm3 with ~2.3 microns lateral and ~9.2 microns axial resolution. Applying the mesoscopic OPM, we demonstrate in vivo and in toto whole organism imaging of the zebrafish vasculature and its endothelial nuclei, and blood flow dynamics at 12 Hz acquisition rate, resulting in a quantitative map of blood flow across the entire organism.

Recent advances in oblique plane microscopy

Oblique plane microscopy (OPM) directly captures object information in a plane tilted from the focal plane of the objective lens without the need for slow z-stack acquisition. This unconventional widefield imaging approach is made possible by using a remote focusing principle that eliminates optical aberrations for object points beyond the focal plane. Together with oblique lightsheet illumination, OPM can make conventional lightsheet imaging fully compatible with standard biological specimens prepared on microscope slides. OPM is not only an excellent high-speed volumetric imaging platform by sweeping oblique lightsheet illumination without mechanically moving either the sample or objective lens in sample space, but also provides a solution for direct oblique plane imaging along any orientation of interest on the sample in a single shot. Since its first demonstration in 2008, OPM has continued to evolve into an advanced microscope platform for biological, medical, and materials science applications. In recent years, many technological advances have been made in OPM with the goal of super-resolution, fast volumetric imaging, and a large imaging field of view, etc. This review gives an overview of OPM's working principle and imaging performance and introduces recent technical developments in OPM methods and applications. OPM has strong potential in a variety of research fields, including cellular and developmental biology, clinical diagnostics in histology and ophthalmology, flow cytometry, microfluidic devices, and soft materials.

Light-sheets and smart microscopy, an exciting future is dawning

Light-sheet fluorescence microscopy has transformed our ability to visualize and quantitatively measure biological processes rapidly and over long time periods. In this review, we discuss current and future developments in light-sheet fluorescence microscopy that we expect to further expand its capabilities. This includes smart and adaptive imaging schemes to overcome traditional imaging trade-offs, i.e., spatiotemporal resolution, field of view and sample health. In smart microscopy, a microscope will autonomously decide where, when, what and how to image. We further assess how image restoration techniques provide avenues to overcome these tradeoffs and how "open top" light-sheet microscopes may enable multi-modal imaging with high throughput. As such, we predict that light-sheet microscopy will fulfill an important role in biomedical and clinical imaging in the future.