Synthesis, Aggregation-Induced Emission Enhancement and Cells Imaging of Water-Soluble Pyridine Naphthalimide-Polyamidoamine Dendrimer

A water-soluble pyridine naphthalimide-polyamidoamine dendrimer (PN-PAMAM) was synthesized by the amidation reaction of 4-(2-vinylpyridine)-1,8-naphthalimide unit and the polyamidoamine (PAMAM). The structure was characterized by H-1 NMR, C-13 NMR, IR and HRMS techniques. PN-PAMAM displayed obvious aggregation-induced emission enhancement (AIEE) behavior. The experimental results demonstrated that dendrimer PN-PAMAM in solid state emitted a yellow-green fluorescence and the maximum emission wavelength was 532 nm. In aqueous solution the maximum emission wavelength was 494 nm and the fluorescence quantum yield was 4.42%. The fluorescence intensity reached the maximum at 60% water volume fraction in H2O/THF mixed solution. The fluorescence emission wavelength was 485 nm and the fluorescence quantum yield was increased to 17.54%. The photophysical properties of the silica nanoparticles loaded AIEE dye PN-PAMAM were examined. The fluorescence emission wavelength was 473 nm and the particle diameter was about 40 nm. In addition, dendrimer PN-PAMAM were applied for breast cancer MCF-7 cells imaging, getting clear blue-field photograph. In summary, the pyridine naphthalimide-PAMAM dendrimer is a water-soluble fluorescent dye and displays AIEE behavior. PN-PAMAM can be widely used in areas of tumor localization, bio-tracking and nano-materials.