Investigation of Newly Prepared Biodegradable 32P-chromic Phosphate-polylactide-co-glycolide Seeds and Their Therapeutic Response Evaluation for Glioma Brachytherapy

32P high-dose rate brachytherapy allows high-dose radiation delivery to target lesions with less damage to adjacent tissues.Te early evaluation of its therapeutic efect on tumours is vital for the optimization of treatment regimes. Te most commonly used 32P-CP colloid tends to leak with blind therapeutic area afer intratumour injection. We prepared 32P-chromic phosphate-polylactide-coglycolide (32P-CP-PLGA) seeds with biodegradable PLGA as a framework and investigated their characteristics in vitro and in vivo. We also evaluated the therapeutic efect of 32P-CP-PLGA brachytherapy for glioma with the integrin pvp3-targeted radiotracer 68Ga-3PRGD2. 32P-CP-PLGA seeds (seed group, SG, 185 MBq) and 32P-CP colloid (colloid group, CG, 18.5 MBq) were implanted or injected into human glioma xenografs in nude mice. Scanning electron microscopy (SEM) of the seeds, micro-SPECT imaging, and biodistribution studies were performed at diferent time points. Te tumour volume was measured using a caliper, and 68Ga3PRGD2 micro-PET-CT imaging was performed to evaluate the therapeutic efect afer 32P intratumour administration.Te delayed release of 32P-CP was observed with biodegradation of vehicle PLGA. Intratumoural efective half-life of 32P-CP in the SG (13.3 ± 0.3) d was longer than that in the CG (10.4 ± 0.3)d(p < 0.05), with liver appearance in the CG on SPECT. A radioactivity gradient developed inside the tumour in the SG, as confrmed by micro-SPECT and SEM. Tumour uptake of 68Ga-3PRGD2 displayed a signifcant increase on day 0.5 in the SG and decreased earlier (on day 2) than the volume reduction (on day 8). Tus, 32P-CPPLGA seeds, controlling the release of entrapped 32P-CP particles, are promising for glioma brachytherapy, and 68Ga-3PRGD2 imaging shows potential for early response evaluation of 32P-CP-PLGA seeds brachytherapy.