FRET-engineering of organic nanoparticles for photoacoustic imaging-guided photodynamic and augmented photothermal therapy

Phototherapy has gained a large amount of attention in tumor treatment due to its non-invasive feature. However, conventional photosensitizers suffer from the deficiency in low photon utilization efficiency, which leads to lower tumor treatment efficiency. In this contribution, a small molecular near-infrared dye BDF was synthesized to construct phototheranostic nanoparticles BDF@PEG-Ce6 NPs for combinational photodynamic therapy (PDT) and enhanced photothermal therapy (PTT). Within BDF@PEG-Ce6 NPs, Ce6 and BDF played the roles of energy donor and energy acceptor, respectively, for the Förster resonance energy transfer (FRET) process. Upon 660 nm photoirradiation, photosensitizer Ce6 within BDF@PEG-Ce6 NPs not only demonstrated photodynamic activity but also served as an energy generator to release energy (donor) to be absorbed by BDF dye with FRET efficiency of 97.7%. Thus, BDF@PEG-Ce6 NPs showed an outstanding photothermal effect, enabling photoacoustic (PA) imaging of tumor sites to guide tumor treatment. It is believed that this work can provide a new idea for the rational design of photosensitizers for better tumor treatment in the future.