Enzymatic Preparation of Hollow Yttrium Oxide Microspheres for In Situ Radiotherapy of Deep‐Seated Cancer

Chemically durable microspheres 20−30 μm in diameter containing a large amount of yttrium are useful for in situ radiotherapy of cancer, as they can be activated by neutron bombardment to form β‐emitters, and can be injected into the vicinity of the cancer cells to impart a large localized dose of β‐radiation. In this study, preparation of hollow Y 2 O 3 microspheres using an enzymatic reaction was attempted, and the structure and chemical durability of the resulting microspheres were investigated. Hollow Y 2 O 3 microspheres 20–30 μm in diameter were successfully prepared by this enzymatic method. The outer surface of the microspheres was smooth and dense, and the inner parts had a honeycombed structure. In simulated body fluids at pH 6 and 7, the hollow Y 2 O 3 microspheres showed high chemical durability.