Synthesis, photophysical characterization, and integration of two-photon-responsive fluorophores in mesoporous organosilica nanoparticles for biological imaging use

We report the synthesis of new graftable three-branched octupolar fluorophores (F and F2), based on a triphenylamine core connected to electron-withdrawing sulfone-based peripheral groups through one or two π-conjugated phenylene-vinylene linkers. Their two-photon absorption (TPA), solvatochromism and photoluminescence properties were investigated to derive structure-property relationships. Notably, the chromophores presented TPA bands in the biological window (700–900 nm) and high TPA cross-sections at peak of 810 GM for F and F2. Then, after silylation, fluorophore F was further covalently integrated within the sol-gel synthesis of different periodic mesoporous organosilica nanoparticles (PMO NPs). Transmission electronic microscopy imaging revealed the formation of spherical NPs with good monodispersity in size, as confirmed by dynamic light scattering measurements. The obtained fluorophore-based nanoplatforms were shown to be biocompatible in vitro and demonstrated a good potential for two-photon imaging in cancer cells using two-photon excited fluorescence microscopy.