Molecular Engineering of NIR-II Excitable Phototheranostic for Mitochondria-Targeted Cancer Photoimmunotherapy.

The advancement of mitochondria-targeted near-infrared-II (NIR-II) excitable phototheranostics constitutes a promising strategy for improving fluorescence-image-guided cancer phototherapy. However, developing phototheranostic agents that simultaneously combine high-contrast NIR-II fluorescence imaging with effective multimodal therapeutic techniques remains a substantial challenge. Herein, we reported a shielding-donor-acceptor-donor-shielding structured NIR-II phototheranostic (FCD-T) by a molecular engineering strategy, followed by self-assembly with glutathione-responsive copolymer to form FCD-T nanoparticles. The introduction of functional bithiophene endows FCD-T with significant electron-donating properties and reduces intermolecular π-π stacking interactions. The robust π-conjugation of fluorene with good rigidity would enhance the intramolecular charge transfer capability. Therefore, FCD-T NPs exhibited an NIR-II absorption peak at 1075 nm and an emission peak at 1280 nm. Upon NIR-II light excitation, such nanoparticles could generate excellent photothermal and photodynamic performances with good biocompatibility. Moreover, the NIR-II mitochondria-targeted phototherapy further facilitated mitochondrial apoptosis-related pathways, activating antitumor immunity and inhibiting tumor growth with single irradiation at low doses.