Radioactive hybrid semiconducting polymer nanoparticles for imaging-guided tri-modal therapy of breast cancer

Due to the rapid progression and aggressive metastasis of breast cancer, its diagnosis and treatment remain a great challenge. The simultaneous inhibition of tumor growth and metastasis is necessary for breast cancer to obtain ideal therapeutic outcomes. We herein report the development of radioactive hybrid semiconducting polymer nanoparticles (SPN_H) for imaging-guided tri-modal therapy of breast cancer. Two semiconducting polymers are used to form SPN_H with a diameter of around 60 nm via nano-coprecipitation and they are also labeled with iodine-131 (¹³¹I) to enhance the imaging functions. The formed SPN_H show good radiolabeling stability and excellent photodynamic and photothermal effects under 808 nm laser irradiation to produce singlet oxygen (¹O₂) and heat. Moreover, SPN_H can generate ¹O₂ with ultrasound irradiation via their sonodynamic properties. After intravenous tail vein injection, SPN_H can effectively accumulate in the subcutaneous 4T1 tumors of living mice as verified via fluorescence and single photon emission computed tomography (SPECT) imaging. With the irradiation of tumors using an 808 nm laser and US, SPN_H mediate photodynamic therapy (PDT), photothermal therapy (PTT) and sonodynamic therapy (SDT) to kill tumor cells. Such a tri-modal therapy leads to an improved efficacy in inhibiting tumor growth and suppressing tumor metastasis compared to the sole SDT and combinational PDT-PTT. This study thus demonstrates the applications of SPN_H to diagnose tumors and combine different therapies for effective breast cancer treatment.