Light-sheet fluorescence microscopy

Light-sheet fluorescence microscopy (LSFM) is a powerful technique for high-speed volumetric functional imaging. However, in typical light-sheet microscopes, the illumination and collection optics impose significant constraints upon the imaging of non-transparent brain tissues. Sacher et al. demonstrated that these constraints can be surmounted using a new class of implantable photonic neural probes. Aim: Mass manufacturable, silicon-based light-sheet photonic neural probes can generate planar patterned illumination at arbitrary depths in brain tissues without any additional micro-optic components. Approach: We develop implantable photonic neural probes that generate light sheets in tissue. The probes were fabricated in a photonics foundry on 200-mm-diameter silicon wafers. The light sheets were characterized in fluorescein and in free space. The probe-enabled imaging approach was tested in fixed, in vitro, and in vivo mouse brain tissues. Imaging tests were also performed using fluorescent beads suspended in agarose. Results: The probes had 5 to 10 addressable sheets and average sheet thicknesses < 16 μ m for propagation distances up to 300 μ m in free space. Imaging areas were as large as ≈ 240 μ m × 490 μ m in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy.

The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals ¹⁾.