A Bi₂O₃-TiO₂ Heterojunction for Triple-Modality Cancer Theranostics

Owing to the limitations of single-mode cancer treatments, combination therapies have attracted much attention. However, constructing a platform for combination therapies in a simple and effective way and improving the overall treatment effect remains a challenge. Our aim was to combine sonodynamic therapy, radiotherapy and chemotherapy together and improve therapeutic outcomes within one nanoplatform.

In this work, we sought to exploit the properties of nanoscale heterojunctions to this end. A multifunctional Bi₂O₃-TiO₂@polydopamine-doxorubicin (BTPD) nanoparticle platform was constructed as an anti-cancer theranostic. Under ultrasound irradiation, the Bi₂O₃-TiO₂ core can generate singlet oxygen to damage tumor cells. Meanwhile, the high-Z Bi₂O₃ can attenuate the energy of X-rays and scatter secondary electrons to enhance radiation damage in the tumor. A thin coating of polydopamine (PDA) increases the biocompatibility but also gives the particles the ability for photoacoustic imaging. Doxorubicin, a DNA repair inhibitor which can hinder tumor recovery from radiation damage, was loaded onto the PDA.

A comprehensive series of in vitro and in vivo assays demonstrated that the nanoparticles were effectively taken up into cancer cells, where they could induce ROS production and cause cell death. In vivo, this led to a marked reduction in tumor volume in a murine 4T1 cancer model.

The formulations developed here have significant potential for future investigation and exploration in the treatment of cancer.