Engineered injectable alginate hydrogel for radiotherapy spacing: Achieving controllable degradation and real-time imaging tracking.

Radiation therapy, a core cancer treatment, uses high-energy rays to kill tumor cells but damages surrounding healthy tissues, limiting efficacy and causing side effects. Thus, protecting normal tissues is key to better radiotherapy outcomes. Spacers form a physical barrier between normal and tumor tissues to reduce radiation to healthy cells, vital for protection. However, current spacers are non-degradable, lack imaging capabilities, or have poor biocompatibility, hindering monitoring during treatment and safe metabolism post-treatment. This study developed an injectable calcium alginate hydrogel. By adjusting calcium concentration, the optimal SA-Ca2+-3 was determined. Adding iodinated oil enables real-time CT monitoring of its position/status during treatment; introducing diethylenetriaminepentaacetic acid post-radiotherapy allows precise, controlled degradation, resolving metabolism issues. Tests in subcutaneous and prostate models confirmed SA-Ca2+-3 stays stable in vivo for 30 days with good biocompatibility and no obvious inflammation. With controllable degradation, visualized imaging, and optimized mechanics, it may become an ideal radiation spacer, offering a new strategy to boost radiotherapy safety and precision.