Novel near-infrared fluorescent probe for live cell imaging

Near infrared (NIR) fluorescent probes play a crucial role in biological system imaging. A novel NIR fluorescent probe, IR787, was designed in the present study. Compared with indocyanine green (ICG), IR787 showed lower background fluorescent interference and higher fluorescence enhancement. Fluorescence intensities were detected by a Cary Eclipse fluorescence spectrophotometer. The interference of intracellular ions (Cu²⁺, Ca²⁺, Mg²⁺ and Zn²⁺) on the measurement was negligible, which indicated a good photostability of IR787. MTT assay demonstrated that cell viability of human lung adenocarcinoma epithelial cell line A549 was not significantly affected by the use of the IR787 probe compared with the ICG probe. This result suggested that the IR787 probe was safe for in vitro cell imaging. In vitro NIR optical imaging experiments further revealed cellular uptake and strong intracellular NIR fluorescence of the IR787 probe in A549 cells. The excitation wavelength was 787 nm for IR787. Compared with the previously reported NIR fluorescent probe ICG, the IR787 NIR fluorescent probe had improved prospects for intracellular imaging. IR787 may play a pivotal role in the understanding cell biology, pharmacology and disease diagnosis.