Fiber bundle-based integrated platform for wide-field fluorescence imaging and patterned optical stimulation for modulation of vasoconstriction in the deep brain of a living animal

Abstract

Abstract:We report a fiber optics-based intravital fluorescence imaging platform that includes epi-fluorescence microscopy and laser patterned-light stimulation system. The platform can perform real-time fluorescence imaging with a lateral resolution of ~4.9 μm while directly inserted into the intact mouse brain, optically stimulate vasoconstriction during real-time imaging, and avoid vessel damage in the penetration path of imaging probe. Using 473-nm patterned-light stimulation, we successfully modulated the vasoconstriction of a single targeted 37-μm-diameter blood vessel located more than 4.7 mm below the brain surface of a live SM22-ChR2 mouse. This platform may permit the hemodynamic studies associated with deeper brain neurovascular disorders.

Fabrication and characterization of large numerical aperture, high-resolution optical fiber bundles based on high-contrast pairs of soft glasses for fluorescence imaging

“…Minimum core diameter and core-tocore distance values of 1.6 µm and 2.3 μm were sufficient for eliminating the optical crosstalk between individual cores even in the presence of bending for both sets of glass compositions. FBs 2, 4-7 have pixel sizes similar to the ones previously reported by other groups (NA = 0.4; core diameter = 2.2 µm; core-to-core distance<4 µm in Ref [31], NA = 0.27; core diameter = 1.8 µm; core-to-core distance~3.5 µm in Ref [41]), but offer much larger NA. As a result, they can collect higher fluorescent signal and achieve higher contrast values especially in fluorescence imaging.…”

“…FBs can be used for imaging without the requirement of a scanning mechanism at the distal end of the fiber [24,25], and they can be incorporated in more sophisticated imaging systems that use confocal [24,26,27] or structured light illumination approaches [28][29][30]. Several recent microscopic imaging demonstrations using FBs include: deep-brain imaging of a living animal [31], in vivo subcellular resolution imaging of cancerous tissues such as oral, cervical and ovarian [32][33][34][35], ex-vivo human stomach, animal colon, liver and belly tissue imaging [36], and thermal infrared imaging [37][38][39][40]. Currently best FBs dedicated for fluorescent imaging have pixel sizes larger than 3 μm and NA values smaller than 0.40 [31,41].…”

“…Several recent microscopic imaging demonstrations using FBs include: deep-brain imaging of a living animal [31], in vivo subcellular resolution imaging of cancerous tissues such as oral, cervical and ovarian [32][33][34][35], ex-vivo human stomach, animal colon, liver and belly tissue imaging [36], and thermal infrared imaging [37][38][39][40]. Currently best FBs dedicated for fluorescent imaging have pixel sizes larger than 3 μm and NA values smaller than 0.40 [31,41].…”

In vivofluorescence imaging with a flat, lensless microscope

“…However, simultaneously achieving large FOV, cellular resolution (defined here as < 10 μm), and light weight (< 3g for freely moving mice) is extremely difficult. For example, previously reported miniature microscopes with cellular resolution have a FOV < 0.5 mm 2 ( Supplementary Table 1) 5,6,10,11 . Miniature microscopes with a large FOV that can cover the entire mouse cortex must compromise spatial resolution to approximately 40 μm 8 .…”

Integrative microendoscopic system combined with conventional microscope for live animal tissue imaging

“…By supplying micron‐scale probes for microscopic imaging of living tissue , minimally invasive imaging procedure could be possible, while extending the potential working range of microscopy beyond the objective tip . Recent advances in the miniaturization of small‐diameter fiber bundles and GRIN (Gradient‐index) lenses have enabled in vivo imaging of the mouse brain, kidney, and liver, as well as monitoring of tumor progression in murine colon models . While less common in human applications, small‐diameter confocal microendoscopic probes have been applied to visualize the bronchial tubes and airways in vivo , as well as in gynecology and pediatrics.…”