A series of fluorenone-based
two-photon fluorescent probes with
high photostability for nucleus imaging are prepared and developed.
The one- and two-photon photophysical properties exhibit these new
probes possess 0.448–0.634 of fluorescence quantum yields and
469–495 GM of two-photon absorption cross sections at 800 nm
femtosecond laser excitation. The luminescence “turn-on”
experiment in buffer solutions indicates that 35-fold of fluorescence
intensity and 68-fold fluorescence quantum yield enhancement appear
between new probes and calf thymus DNA. In the nuclear double-staining
experiment, the high mean colocalization coefficients of 0.92–0.96
between new probes and nuclear labeling dye Hoechst 33342 are acquired,
demonstrating excellent nuclear localization in 3T3 cells. The counterstain
studies by introducing commercial mitochondrial staining reagent MTR
and nuclear staining dye DAPI further show good membrane permeability
and counterstain compatibility in multicolor cell labeling application.
The photostability studies show that 3000 s of observation time and
0.028%/s–0.03%/s of mean fluorescence attenuation rates under
persistent laser irradiation in two-photon nuclear imaging are achieved.
Meanwhile, the cause of fluorescence attenuation in the photostability
test for cellular nuclei monitoring are discussed as well
