Hydrophilic, Red‐Emitting, and Thermally Activated Delayed Fluorescence Emitter for Time‐Resolved Luminescence Imaging by Mitochondrion‐Induced Aggregation in Living Cells

Abstract

Thermally activated delayed fluorescence (TADF) materials have provided new strategies for time‐resolved luminescence imaging (TRLI); however, the development of hydrophilic TADF luminophores for specific imaging in cells remains a substantial challenge. In this study, a mitochondria‐induced aggregation strategy for TRLI is proposed with the design and utilization of the hydrophilic TADF luminophore ((10‐(1,3‐dioxo‐2‐phenyl‐2,3‐dihydro‐1H‐benzo[de]isoquinolin‐6‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridin‐2‐yl)methyl)triphenylphosphonium bromide (NID‐TPP) . Using a nonconjugated linker to introduce a triphenylphosphonium (TPP + ) group into the 6‐(9,9‐dimethylacridin‐10(9 H )‐yl)‐2‐phenyl‐1H‐benzo[ de ]isoquinoline‐1,3(2 H )‐dione (NID) TADF luminophore preserves the TADF emission of NID‐TPP . NID‐TPP shows clear aggregation‐induced delayed fluorescence enhancement behavior, which provides a practical strategy for long‐lived delayed fluorescence emission in an oxygen‐containing environment. Finally, the designed mitochondrion‐targeting TPP + group in NID‐TPP induces the adequate accumulation of NID‐TPP and results in the first reported TADF‐based time‐resolved luminescence imaging and two‐photon imaging of mitochondria in living cells.

Structural Design of Blue‐to‐Red Thermally‐Activated Delayed Fluorescence Molecules by Adjusting the Strength between Donor and Acceptor

“…Red TADF materials are necessary for white OLEDs, and they have potential applications in bioimaging, [68] sensors, [69] nightvision devices [70] and optical communications. [71] On the basis of the energy-gap law, the non-radiative decay rate aggrandizes with red-shift in emission, [72] resulting in a sharp decrease PLQY of TADF emitters in the long-wavelength region.…”

TADF Dye-Loaded Nanoparticles for Fluorescence Live-Cell Imaging

“…Since most TADF dyes are weakly soluble in water and show very weak luminescence in polar solvents due to their charge transfer properties, their direct use in biological media has been critically hindered. To overcome these drawbacks, TADF emitters have been encapsulated in macromolecules (Xiong et al, 2014), precipitated onto nanoaggregates (Ni et al, 2018(Ni et al, , 2019Zhu et al, 2018) or assembled in amphiphilic polymer micelles with other small-molecular-weight dopants (Li et al, 2017;Luo et al, 2019;Tsuchiya et al, 2019). In addition, we previously reported the preparation of TADF emitting silica nanoparticles using a simple doping procedure with a silane-bearing TADF derivative (Crucho et al, 2020).…”

Modulating the Electron‐Donating Ability of Acridine Donor Units for Orange–Red Thermally Activated Delayed Fluorescence Emitters

“…Polymers containing similar emitting units with NAI as an acceptor were applied in ratiometric temperature sensing [30] . Our group also reported NAI‐based TADF emitters with high horizontal orientation, [31] different emission spectra, [19] and time‐resolved luminescence imaging ability [32] . All of this research proved the advantages of NAI if employed as the acceptor unit of TADF emitters.…”