Deep Penetration Microscopic Imaging with Non-Diffracting Airy Beams

Dynamic Volumetric Imaging of Mouse Cerebral Blood Vessels In Vivo with an Ultralong Anti-Diffracting Beam

Volumetric imaging of a mouse brain in vivo with one-photon and two-photon ultralong anti-diffracting (UAD) beam illumination was performed. The three-dimensional (3D) structure of blood vessels in the mouse brain were mapped to a two-dimensional (2D) image. The speed of volumetric imaging was significantly improved due to the long focal length of the UAD beam. Comparing one-photon and two-photon UAD beam volumetric imaging, we found that the imaging depth of two-photon volumetric imaging (80 μm) is better than that of one-photon volumetric imaging (60 μm), and the signal-to-background ratio (SBR) of two-photon volumetric imaging is two times that of one-photon volumetric imaging. Therefore, we used two-photon UAD volumetric imaging to perform dynamic volumetric imaging of mouse brain blood vessels in vivo, and obtained the blood flow velocity.

Ultra-long anti-diffracting beam volume imaging using a single-photon excitation microscope

We studied a novel volumetric single-photon excitation microscope with an ultralong anti-diffracting (UAD) beam as illumination. Volumetric fluorescence image direct mapping showed that the axial imaging range of the UAD beam was approximately 14 times and 2 times that of conventional Gaussian and Airy beams, respectively, while maintaining a narrow lateral width. We compared the imaging capabilities of the Gaussian, Airy, and UAD modes through a strongly scattering environment mixed with fluorescent microspheres and agarose gel. Thick samples were scanned layer by layer in the Gaussian, Airy, and UAD modes, and then the three-dimensional structural information was projected onto a two-dimensional image. Benefiting from the longer focal length of the UAD beam, a deeper axial projection was provided, and the volume imaging speed was vastly increased. To demonstrate the performances of the UAD microscope, we performed dynamic volumetric imaging on the cardiovascular system of zebrafish labeled with green fluorescent proteins in the three modes and dynamically monitored substance transport in zebrafish blood vessels. In addition, the symmetrical curve trajectory of the UAD beam and the axial depth of the lateral position can be used for localization of micro-objects.

Foregut organ progenitors and their niche display distinct viscoelastic properties in vivo during early morphogenesis stages

Material properties of living matter play an important role for biological function and development. Yet, quantification of material properties of internal organs in vivo, without causing physiological damage, remains challenging. Here, we present a non-invasive approach based on modified optical tweezers for quantifying sub-cellular material properties deep inside living zebrafish embryos. Material properties of cells within the foregut region are quantified as deep as 150 µm into the biological tissue through measurements of the positions of an inert tracer. This yields an exponent, α, which characterizes the scaling behavior of the positional power spectra and the complex shear moduli. The measurements demonstrate differential mechanical properties: at the time when the developing organs undergo substantial displacements during morphogenesis, gut progenitors are more elastic (α = 0.57 ± 0.07) than the neighboring yolk (α = 0.73 ± 0.08), liver (α = 0.66 ± 0.06) and two mesodermal (α = 0.68 ± 0.06, α = 0.64 ± 0.06) progenitor cell populations. The higher elasticity of gut progenitors correlates with an increased cellular concentration of microtubules. The results infer a role of material properties during morphogenesis and the approach paves the way for quantitative material investigations in vivo of embryos, explants, or organoids.

Here, the authors present a method based on optical tweezers to measure mechanical properties of cells inside living zebrafish embryos. The measurement reveals spatiotemporally distinct mechanical properties, linking cell mechanics and morphogenesis.