Conditional nucleic acid sensors for highly spatial and temporal resolution of bioimaging

High-resolution imaging of dynamic molecular targets within living organisms is essential for comprehensive understanding of complex biological processes. DNA sensors have emerged as powerful tools for the sensing and imaging of a wide range of molecules. However, conventional DNA sensors are usually in an "always active" state, which may result in false positive signals and low temporal and spatial resolutions in complex cellular or in vivo environments. To meet these challenges, conditional DNA sensors are developed by integrating molecular switches into conventional DNA sensors, whose reactivity are shielded until being activated by certain stimulations. To better understand the development of conditional DNA sensors and accelerate their applications in bioimaging, we review the recent progress in the design of conditional DNA sensors for bioimaging, focusing on exogenous and endogenous stimulation strategies. Also, we discuss the challenges and opportunities of the construction and application of activating DNA fluorescence sensors under specific conditions.