Far Red/Near-Infrared AIE Dots for Image-Guided Photodynamic Cancer Cell Ablation

We report a facile encapsulation approach to realize bright far red/near-infrared (FR/NIR) fluorescence and efficient singlet oxygen COD production of organic fluorogens with aggregation-induced emission (AIEgen) and intramolecular charge transfer (ICT) characteristics for image-guided photodynamic cancer cell ablation. The synthesized AIEgen BTPEAQ possesses donor-acceptor-donor structure, which shows bright fluorescence in solid state. Due to the strong ICT effect, BTPEAQ exhibits poor emission with almost no O-1(2) generation in aqueous solution. Encapsulation of BTPEAQ by DSPE-PEG block copolymer yields polymer-shelled dots, which show enhanced brightness with a fluorescence quantum yield of 3.9% and a O-1(2) quantum yield of 38%. Upon encapsulation by silica, the formed SiO2-shelled dots show much improved fluorescence quantum yield of 12.1% but with no obvious O-1(2) generation. This study clearly demonstrates the importance of encapsulation approach for organic fluorophores, which affects not only the brightness but also the O-1(2) production. After conjugating the polymer-shelled AIE dots with cRGD peptide, the obtained BTPEAQ-cRGD dots show excellent photoablation toward MDA-MB-231 cells with integrin overexpression while keeping control cells intact.