Novel Bio-Imaging Techniques Based on Molecular Switching

Fluorescence microscopy has been a fundamental imaging tool for life science research. Fluorescence basically involves only two molecular states: the ground molecular state and the first singlet excited state (the fluorescent state). Astonishingly, it greatly diversified the applicability of fluorescence microscopy in many different ways by incorporating additional molecular states and switching fluorescent molecules through these three or even more molecular states during the fluorescence process. This switching mechanism between additional molecular states, either long lifetime or short lifetime, and two original molecular states actually adds nonlinearity into the linear fluorescence process, which empowers fluorescence microscopy additional imaging capabilities. Herein, we developed four distinct new imaging techniques by taking advantage of this molecular switching mechanism: dark state dynamics sensing and imaging by fluorescence anomalous phase advance, genetically-encoded microviscosity sensor using protein-flexibility mediated photochromism, deep tissue imaging with super-nonlinear fluorescence microscopy, and light-driven fluorescent timer for simultaneous spatial-tempora