Implantable Photonic Neural Probes For Light-Sheet Fluorescence Brain Imaging

Significance: 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. We demonstrate 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 mu m for propagation distances up to 300 mu m in free space. Imaging areas were as large as approximate to 240 mu m x 490 mu m in brain tissue. Image contrast was enhanced relative to epifluorescence microscopy.Conclusions: The neural probes can lead to new variants of LSFM for deep brain imaging and experiments in freely moving animals. (C) The Authors.