Enhancing singlet oxygen generation in semiconducting polymer nanoparticles through fluorescence resonance energy transfer for tumor treatment.

Qiang Zhao,Zihan Xu,Jiayang Jiang,Mingjuan Xie,Shujuan Liu,Zhuang Lv,Yuanyuan Qian,Wei Huang,Peng Tao

doi:10.1039/c8sc05501g

Abstract

Photosensitizers (PSs) are of particular importance for efficient photodynamic therapy (PDT). Challenges for PSs simultaneously possessing strong light-absorbing ability, high 1O2 generation by effective intersystem crossing from the singlet to the triplet state, good water-solubility and excellent photostability still exist. Reported here are a new kind of dual-emissive semiconducting polymer nanoparticles (SPNs) containing fluorescent BODIPY derivatives and near-infrared (NIR) phosphorescent iridium(iii) complexes. In the SPNs, the BODIPY units serve as the energy donors in the fluorescence resonance energy transfer (FRET) process for enhancing the light absorption of the SPNs. The NIR emissive iridium(iii) complexes are chosen as the energy acceptors and efficient photosensitizers. The ionized semiconducting polymers can easily self-assemble to form hydrophilic nanoparticles and homogeneously disperse in aqueous solution. Meanwhile, the conjugated backbone of SPNs provides effective shielding for the two luminophores from photobleaching. Thus, an excellent overall performance of the SPN-based PSs has been realized and the high 1O2 yield (0.97) resulting from the synergistic effect of BODIPY units and iridium(iii) complexes through the FRET process is among the best reported for PSs. In addition, owing to the phosphorescence quenching of iridium(iii) complexes caused by 3O2, the SPNs can also be utilized for O2 mapping in vitro and in vivo, which assists in the evaluation of the PDT process and provides important instructions in early-stage cancer diagnosis.

Highlights

Photodynamic therapy (PDT) with high optical precision has attracted tremendous attention as an emerging clinical modality for treating cancers, which brings little damage to normal tissues, no wound surface, and negligible long-term sequelae or immune attack.[1,2] During the PDT process, photosensitizers (PSs), which convert 3O2 to 1O2 or other reactive oxygen species (ROS) under light irradiation, play a crucial role in the irreversible cytotoxic process to cancer cells.[3,4] In order to achieve effective PDT, high 1O2 production via an effective intersystem crossing (ISC) from the singlet (S1) to the triplet state (T1), intense light absorption, good photostability and water-solubility should be required for PSs
Attributed to the rational structural design, together with the synergistic effect of BODIPY units and iridium(III) complexes through a highly efficient fluorescence resonance energy transfer (FRET) process, a high 1O2 quantum yield (0.97) of semiconducting polymer nanoparticles (SPNs) has been achieved, which is among the best reported for PSs
In the SPNs, the BODIPY units served as the energy donors in the FRET process and enhanced the light absorption ability of the SPNs

Summary

Introduction

Photodynamic therapy (PDT) with high optical precision has attracted tremendous attention as an emerging clinical modality for treating cancers, which brings little damage to normal tissues, no wound surface, and negligible long-term sequelae or immune attack.[1,2] During the PDT process, photosensitizers (PSs), which convert 3O2 to 1O2 or other reactive oxygen species (ROS) under light irradiation, play a crucial role in the irreversible cytotoxic process to cancer cells.[3,4] In order to achieve effective PDT, high 1O2 production via an effective intersystem crossing (ISC) from the singlet (S1) to the triplet state (T1), intense light absorption, good photostability and water-solubility should be required for PSs. R0i À Ri R0i where Q is the quenching efficiency value, and Ri and R0i are the emission intensity ratio (I704 nm/I515 nm) at different oxygen contents and in nitrogen, respectively.

Results

Conclusion