A versatile 980 nm excitable small molecule for short-wave infrared fluorescence imaging guided type-I photodynamic/photothermal therapy

Abstract

Current nanoagents for efficient deep-seated tumor phototheranostics are still facing many barriers, such as limited light penetration depth, insufficient reactive oxygen species production in anaerobic microenvironment, and dissatisfied imaging accuracy. Herein, an A-D-A type small molecule BTP-3V was synthesized. The strong push-pull effect enabled BTP-3V nanoparticles (NPs) to absorb light in the region of 600–1100 nm (extinction coefficient at 980 nm: 3.92 × 10⁴ M⁻¹ cm⁻¹) and emit in the region of 1000–1400 nm (Stokes shift: 283 nm). Upon 980 nm laser excitation, BTP-3V NPs showed efficient hydroxyl radical and superoxide radical production for type-I photodynamic therapy, greatly overcoming the anaerobic disadvantage of malignant tumors. Moreover, the NPs also showed excellent photothermal performance with high photothermal conversion efficiency (39.4 %). In vitro and in vivo investigations corroborated that the biocompatible BTP-3V NPs exhibited remarkable anti-tumor outcome upon 980 nm laser irradiation, benefiting from the combination of type-I photodynamic and photothermal therapy. Significantly, with the short-wave infrared fluorescence emission, BTP-3V NPs could achieve high-resolution imaging of vascular structure, accurate localization of tumor and facile detection of the enrichment and distribution of NPs within the tumor. This study provides valuable insights into nanomaterials for deep-tissue phototheranostics.