Two-photon ratiometric fluorescent probe based on NBD-amine functionalized semiconducting polymer nanoparticles for real-time imaging of hydrogen sulfide in living cells and zebrafish.

The thiolysis of 7-nitro-1,2,3-benzoxadiazole amine (NBD-A) paves the way for specific sensing of HS over biothiols and real-time imaging in living organisms. Rational fabrication of NBD-A-based probe with ratiometric mode and two-photon excitation is highly appealing to achieve high quality bioimaging. In this work, the NBD-A molecules are assembled with poly(9,9-dioctylfluorenyl-2,7-diyl) polymer nanoparticles, defined as NBD@PFO, to construct two-photon ratiometric probes for HS detection through the fluorescence resonance energy transfer (FRET). For the construction of NBD@PFO nanohybrids, polymer nanoparticles are employed as the NBD-A molecular vehicle, energy donor and two-photon absorber, while NBD-A is served as the response unit and energy acceptor. Taking advantages of NBD-A and polymer nanoparticles, the obtained NBD@PFO probes exhibit high selectivity, fast response (<5 s), ratiometric detection and two-photon excitation. Our results indicate that NBD@PFO nanohybrids are successfully applied for monitoring of HS concentration in living cells and zebrafish, exhibiting great potential of polymer nanoparticles to improve the imaging capability of an organic small molecular probe.