A novel triphenylamine-BODIPY based Schiff base fluorescent probe (TPA-BODIPY-OH) with an emission in the near-infrared (NIR) region was designed and prepared by click reaction. TPA-BODIPY-OH showed three emission bands at 510 nm, 598 nm and 670 nm, and can detect Fe3+ and Hg2+ ions with remarkable fluorescence enhancement in THF/H2O (v/v, 1 : 1, buffered with 10 mM HEPES pH = 7.4) based on the hydrolysis reaction of the –CN bond, and naked eye detection was realized with an obvious color change. The stoichiometry between the probe and ions was deduced from a Job's plot, which is 1 : 3 for TPA-BODIPY-OH/Fe3+ and 1 : 2 for TPA-BODIPY-OH/Hg2+, respectively. The dissociation constant value was found to be 1.35 × 10−16 M for TPA-BODIPY-OH/Fe3+ and 2.06 × 10−11 M for TPA-BODIPY-OH/Hg2+. The low detection limit was calculated from the titration results with the values of 5.15 × 10−7 M for TPA-BODIPY-OH/Fe3+ and 6.81 × 10−7 M for TPA-BODIPY-OH/Hg2+, respectively. In order to investigate the biological applications of TPA-BODIPY-OH, a living cell imaging experiment was carried out. The results demonstrate that TPA-BODIPY-OH can be successfully applied as a bioimaging agent in living cells. In addition, amino-group-functionalized silica fluorescent nanoparticles (FNPs) encapsulating the TPA-BODIPY-OH dyes were prepared and characterized by transmission electron microscopy. TPA-BODIPY-OH/SiO2 nanoparticles exhibit good dispersibility, and the quantum yield of FNPs at 657 nm was 42.3%.
In this paper, the heavy-atom-free BODIPY dendrimer TM4-BDP was synthesized for the near-infrared photodynamic therapy, which was composed of the triphenylamine-BODIPY dimer and four 1-(2-morpholinoethyl)-1H-indole-3-ethenyl groups. The TM4-BDP could achieve the near-infrared photodynamic therapy through two different photosensitive pathway, which include the one-photon excitation at 660 nm and two-photon excitation at 1000 nm. In the one-photon excitation pathway, the TM4-BDP could generate singlet oxygen and superoxide radical under 660 nm illumination. In addition, the one-photon PDT experiment in human nasopharyngeal carcinoma (CNE-2) cells also indicated that the TM4-BDP could specific accumulate in lysosomes and shown great cell phototoxicity with the IC50 at 22.1μM. In the two-photon excitation pathway, the two-photon absorption cross section at 1030 nm of TM4-BDP was determined as 383 GM, which make it could generate the reactive oxygen species (ROS) under 1000 nm femtosecond laser excitation. Moreover, the two-photon PDT experiment in zebrafish also indicated the TM4-BDP could be used for the two-photon fluorescence imaging and the two-photon induced ROS generation in biological environment. Besides that, in the ROS generation mechanism aspect, the TM4-BDP employ the novel spin-vibronic coupling intersystem crossing (SV-ISC) process for the mechanism of ROS generation and the femtosecond transient absorption spectra indicated that this novel SV-ISC mechanism was closely related with its’ lifetime of charge transfer state. These above experiments of TM4-BDP demonstrate that the dendrimer design was an effective strategy for constructing heavy-atom-free NIR BODIPY photosensitizers and lay the foundation for the two-photon photodynamic therapy in the future clinical trails.
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