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

Abstract

© 2016 American Chemical Society. We report a facile encapsulation approach to realize bright far red/near-infrared (FR/NIR) fluorescence and efficient singlet oxygen (1O2) 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 1O2 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 1O2 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 1O2 generation. This study clearly demonstrates the importance of encapsulation approach for organic fluorophores, which affects not only the brightness but also the 1O2 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.