IMPROVED RADIOSENSITIVE MICROCAPSULES USING H₂O₂

The radiation-induced releasing of the liquid-core of the microcapsules was improved using H₂O₂, which produced O₂ generation of H₂O₂ after irradiation. Further, we tested whether these microcapsules enhanced the antitumor effects and decreased the adverse effects in vivo in C3He/J mice. The capsules were produced by spraying a mixture of 3.0% hyaluronic acid, 2.0% alginate, 3.0% H₂O₂, and 0.3 mmol of carboplatin on a mixture of 0.3 molFeCl₂ and 0.15 molCaCl₂. The microcapsules were subcutaneously injected into MM46 tumors that had been inoculated in the left hind legs of C3He/J mice. The radiotherapy comprised tumor irradiation with 10 Gy or 20 Gy ⁶⁰Co. The antitumor effect of the microcapsules was tested by measuring tumor size and monitoring tumor growth. Three types of adverse effects were considered: fuzzy hair, loss of body weight, and death. The size of the capsule size was 23 ± 2.4 µmɸ and that of the liquid core, 20.2 ± 2.2 µmɸ. The injected microcapsules localized drugs around the tumor. The production of O₂ by radiation increased the release of carboplatin from the microcapsules. The antitumor effects of radiation, carboplatin, and released oxygen were synergistic. Localization of the carboplatin decreased its adverse effects. However, the H₂O₂ caused ulceration of the skin in the treated area. The use of our microcapsules enhanced the antitumor effects and decreased the adverse effects of carboplatin. However, the skin-ulceration caused by H₂O₂ must be considered before these microcapsules can be used clinically.