A Robust Oxygen Microbubble Radiosensitizer for Iodine-125 Brachytherapy

Area of Science:

• Oncology
• Radiotherapy
• Biomaterials

Background:

• Hypoxic microenvironments in solid tumors cause radioresistance to Iodine-125 (¹²⁵I) brachytherapy, limiting treatment effectiveness.
• Developing strategies to reoxygenate tumors is crucial for improving radiotherapy outcomes.

Purpose of the Study:

• To sensitize hypoxic tumors for ¹²⁵I brachytherapy using ultrasound-activated oxygen microbubbles.
• To develop and evaluate novel oxygen/sulfur hexafluoride microbubbles (OS MBs) for enhanced radiotherapy.

Main Methods:

• A modified emulsion freeze-drying method was used to create stable, lyophilized OS MBs.
• OS MBs were administered to nasopharyngeal carcinoma (CNE2) tumor-bearing mice.
• Ultrasound irradiation triggered in situ oxygen release from OS MBs to alleviate tumor hypoxia.

Main Results:

• Ultrasound-triggered OS MBs effectively delivered oxygen, instantly relieving tumor hypoxia.
• Combined therapy of ¹²⁵I brachytherapy and ultrasound-activated OS MBs showed significantly improved therapeutic efficacy compared to brachytherapy alone.
• OS MBs demonstrated a longer half-life compared to traditional oxygen microbubbles.

Conclusions:

• Ultrasound-mediated oxygen delivery using developed OS MBs is a promising strategy to enhance ¹²⁵I brachytherapy efficacy in hypoxic tumors.
• This approach offers a potential solution to overcome hypoxia-induced radioresistance.