Cellular resolution multiplexed FLIM tomography with dual-color Bessel beam

Three Dimensional Lifetime-Multiplex Tomography Based on Time-Gated Capturing of Near-Infrared Fluorescence Images

We report a computed tomography (CT) technique for mapping near-infrared fluorescence (NIRF) lifetime as a multiplex three-dimensional (3D) imaging method, using a conventional NIR camera. This method is achieved by using a time-gated system composed of a pulsed laser and an NIR camera synchronized with a rotatable sample stage for NIRF-CT imaging. The fluorescence lifetimes in microsecond-order of lanthanides were mapped on reconstructed cross-sectional and 3D images, via back-projection of two-dimensional projected images acquired from multiple angles at each time point showing fluorescence decay. A method to select slopes (the observed decay rates in time-gated imaging) used for the lifetime calculation, termed as the slope comparison method, was developed for the accurate calculation of each pixel, resulting in reduction of image acquisition time. Time-gated NIRF-CT provides a novel choice for multiplex 3D observation of deep tissues in biology.

Fourier Multiplexed Fluorescence Lifetime Imaging

Fluorescence lifetime imaging microscopy (FLIM) is a widely used functional imaging method in bioscience. Fourier multiplexed FLIM (FmFLIM), a frequency-domain lifetime measurement method, explores the principle of Fourier (frequency) multiplexing to achieve parallel lifetime detection on multiple fluorescence labels. Combining FmFLIM with a confocal scanning microscope allows multiplexed 3D lifetime imaging of cells and tissues. FmFLIM can also be integrated with the scanning laser tomography imaging method to perform 3D multiplex lifetime imaging of whole embryos and thick tissues.

Three-dimensional live multi-label light-sheet imaging with synchronous excitation-multiplexed structured illumination

Multiplexed imaging is a powerful tool for studying complex interactions inside biological systems. Spectral imaging methods that capture multiple fluorescent markers synchronously without sacrificing the imaging speed or resolution are most suitable for live imaging. We describe spectral-encoded structured illumination (spectral-SIM) light-sheet microscopy, which enables parallel multi-excitation-channel imaging in 3D. Spectral-SIM encodes the excitation wavelength as the phase of the illumination pattern, and allows synchronous image capture over multiple excitation channels at the same speed and spatial resolution as mono-channel structured light-sheet imaging. The technique retains structured light-sheet microscopy's ability in removing out-of-focus and scattered emission background, and generates clear 3D multiplexed images in thick tissue. The capability of this technique was demonstrated by the imaging of live triple-labeled transgenic zebrafish to over 300 μm deep with 0.5μm-by-2μm (lateral-by-axial) resolution.