Nucleoside-Based Ultrasensitive Fluorescent Probe for the Dual-Mode Imaging of Microviscosity in Living Cells

Microviscosity changes of living cells have a far-reaching influence on diffusion and movement capacity of RNA and, more seriously, could modify RNA functions in living cells. Fluorescent rotor, whose fluorescence responds to different environmental viscosities, holds great potential for the imaging of viscosity in biosystem. Although many fluorescent rotors have been reported for viscosity, the fluorogenic rotor with ultrasensitivity for the determination of microviscosity (<10 cP) was rarely reported. Herein, we report a nucleoside-based two-photon fluorescent rotor (dABp-3) that can selectively and ultrasensitively image microviscosity in RNA region of living cells for the first time. 2'-Deoxyadenosine is selected as an electron donor to permit energy transfer via the acetylenic bond to acceptor, a typical boron dipyrromethene moiety. Another highlight, dABp-3 is based on 2'-deoxyadenosine, which result in its recognition capacity for RNA. dABp-3 with ultrasensitivity provides a varied linear response to the microrange viscosity (1.8-6.0 cP) in RNA region of living cells on dual-mode-two-photon ratio mode and fluorescence lifetime mode. After screening and optimization, advantageously, dABp-3 can be used to screen reticulocytes from mature blood cells of thrombosis models in vitro and in vivo because of targeting RNA, while simultaneously image microviscosity changes in these cells. So, dABp-3 as an analytical tool holds considerable promise for bioimaging and monitoring of microviscosity changes in complex biological systems.