Many efforts have been made to develop near-infrared (NIR)
fluorescent dyes with high efficiency for the NIR
laser-induced
phototherapy of
cancer. However, the low
tumor targetability and high nonspecific tissue uptake of NIR
dyes in vivo limit their applications in preclinical
cancer imaging and
therapy. Among the various NIR
dyes,
squaraine (SQ)
dyes are widely used due to their high molar extinction coefficient, intense fluorescence, and excellent photostability. Previously, benzoindole-derived SQ (BSQ) was prepared by incorporating carboxypentyl benzoindolium end groups into a classical SQ backbone, followed by conjugating with
cyclic RGD peptides for
tumor-targeted imaging. In this study, we demonstrate that the structure-inherent
tumor-targeting BSQ not only shows a high fluorescence quantum yield in serum but also exhibits superior
reactive oxygen species (ROS) generation capability under the 671 nm
laser irradiation for effective
photodynamic therapy (
PDT) in vitro and in vivo. Without targeting
ligands, the BSQ was preferentially accumulated in
tumor tissue 24 h post-injection, which was the optimal timing of the
laser irradiation to induce increments of ROS production. Therefore, this work provides a promising strategy for the development of photodynamic therapeutic SQ
dyes for targeted
cancer therapy.