Improving collection efficiency in two-photon endoscopy with reflective waveguiding.

Two-photon endoscopy based on a gradient-index lens has been widely utilized for studying cellular behaviors in deep-lying tissues with minimal invasiveness in vivo. Although the efficient collection of emitted light is critical to attain high-contrast spatiotemporal information, the intrinsic low numerical aperture of the endoscopic probe poses a physical limitation. We report a simple solution to overcome this limit by incorporating a reflective waveguide ensheathing the endoscopic probe, which improves the collection efficiency by approximately two-fold. We describe its principle, fabrication procedure, optical characterization, and utilities in biological tissues.

µTongue: A Microfluidics-Based Functional Imaging Platform for the Tongue In Vivo.

Intravital fluorescence microscopy is a tool used widely to study multicellular dynamics in a live animal. However, it has not been successfully used in the taste sensory organ. By integrating microfluidics into the intravital tongue imaging window, the µTongue provides reliable functional images of taste cells in vivo under controlled exposure to multiple tastants. In this paper, a detailed step-by-step procedure to utilize the µTongue system is presented. There are five subsections: preparing of tastant solutions, setting up of a microfluidic module, sample mounting, acquiring functional image data, and data analysis. Some tips and techniques to solve the practical issues that may arise when using the µTongue are also presented.

Robust functional imaging of taste sensation with a Bessel beam.

Functional imaging of intact taste cells in response to various tastant solutions poses a technical challenge since the refractive index of the immersion medium dynamically changes during tastant delivery. Critically, the focal shift introduced by high-index tastant solutions has been the fundamental limit in experimental design. Here we seek to address this issue by introducing an axially elongated Bessel beam in two-photon microscopy. Compared to the conventional Gaussian beam, the Bessel beam provides superior robustness to the index-induced focal shift, allowing us to acquire near artifact-free imaging of taste cells in response to a physiological taste stimulus.