Inhibition of metastasis using particles that release chitosan upon radiation: A preliminary study

This study aimed to investigate the effect of the particles releasing chitosan upon exposure to radiation on inhibition of metastasis. A 10 mL solution of water containing 0.2% weight/volume alginate, 0.1% hyaluronic acid, and 100-mg chitosan was sprayed into the vibrating solution through a stainless mesh filter (pore size: 0.8 [Formula: see text]m) using an ultrasound disintegrator, thereby generating chitosan particles. Further, [Formula: see text] particles floating in 0.1 mL normal saline were subcutaneously injected around the 4TI cells-derived tumor in the left hind legs of six-week-old male C3He/N mice. Six hours after injection, tumors were exposed to 10 Gy or 20 Gy of 100-keV soft X-ray radiation. The release of chitosan was expressed as the frequency of ruptured chitosan particles 12 h after radiation. The antimetastatic effect was confirmed by a reduction in the number of metastatic pulmonary nodules 21 days after completion of treatment. More than [Formula: see text]% of the chitosan particles released chitosan in response to radiation. The particles releasing chitosan had a prolonged antimetastatic effect when compared with the particles not releasing chitosan, thereby resulting in a significantly greater antimetastatic effect lasting for four weeks since the completion of treatment, in tumors treated with both 10 Gy and 20 Gy of radiation. Hence, particlizing chitosan could be useful in reducing metastasis in irradiated tumors.