Electrostatic interaction-mediated 1:1 complexes for high-contrast mitochondrial-targeted phosphorescence bioimaging

Organelle-targeted imaging can provide information on cellular functions and intracellular interactions, being significant for disease diagnosis. The use of room-temperature phosphorescence (RTP) in organelle-targeted imaging can fully utilize its unique characteristics of long wavelength and deep penetration. However, this technology has long been plagued by insufficient probe targeting and limited luminous intensity. In this work, we prepared a series of complexes composed of multicationic persulfurated arenes and biomacromolecules via electrostatic interactions in 1:1 stoichiometry for high-contrast mitochondrial-targeted RTP imaging. Such an electrostatic interaction design effectively prevented the self-aggregation of the probes, which is not conducive to mitochondrial targeting. Simultaneously, it suppressed the non-radiative decay to the maximum extent, enabling the probes to exhibit strong RTP signals both in aqueous solution and at the cellular level. Furthermore, the biomacromolecules can serve as carriers for an electrostatic interaction transfer of the persulfurated arenes to mitochondria. This leads to high mitochondrial targeting Pearson's correlation coefficients of the probes and high-contrast RTP imaging effects, as well as the independence of the co-incubated probe concentration. These results provide new insights for the development of targeted imaging technologies.