Modulating Aggregation and Deaggregation Based on Assembling Strategy to Switch on NIR-II Light-Excited Fluorescence for Self-Reporting Viability of Eliminating Cancer Cell

The fabrication of self-reporting photosensitizers (PSs), enabling real-time evaluation of the extent of elimination of cancer cells, holds significant scientific importance in the photodynamic therapy (PDT) process. To address the intrinsic challenge of the short-wavelength light source, this work proposed an innovative approach of rational design second near-infrared (NIR-II, 1000-1700 nm) light-excited fluorescent PS systems (named <b>HOEt-PI</b>, <b>Me-PI</b>, and <b>Et-PI</b>, respectively) through modulating aggregation and deaggregation based on assembling strategy. Therein, the suitable interplanar distance of adjacent <b>Et-PI</b> linked with C-H···π interactions was an idea for relieving compact π···π packing for fluorescent imaging as well as elevating the spin-orbit coupling for reactive oxygen species (ROS) generation. With ROS continuously increasing, <b>Et-PI</b> underwent cell membrane-to-mitochondria migration, ultimately accumulated in nucleoli, symbolizing programmed cell death, thus distinguishing dead/live cells via three-photon fluorescence imaging (excited on 1250 nm) under photogeneration ROS. Meaningfully, the three-photon fluorescence of <b>Et-PI</b> was triggered by RNA of nucleoli, for which the higher signal-to-noise ratio and in-depth fluorescence imaging observed cancer cellular viability. Collectively, the proposed findings presented a constructing strategy for NIR-II light-mediated self-reporting PS for guiding the PDT of deep cancerous tissue in the future.