Dysprosium lithium-borate (DyLB) glass
microspheres have been developed as a biodegradable radiation delivery vehicle for the treatment of
rheumatoid arthritis and other diseases. Radioactive
microspheres of these glasses are intended to be injected into a joint infected with
rheumatoid arthritis to safely deliver a localized dose (100 Gy) of beta radiation. Once injected, the
microspheres react nonuniformly with body fluids. The nonradioactive,
lithium-borate component is dissolved from the glass, whereas the radioactive (165)Dy reacts with
phosphate anions in the body fluids, and becomes "chemically" trapped in a solid,
dysprosium phosphate reaction product that has the same size as the unreacted
microsphere. The glass
microspheres lose approximately 80% of their weight after nonuniform reaction (<1 day), but the
dysprosium phosphate reaction product is slowly metabolized by the body over several months. Ethylenediaminetetraacetate (
EDTA)
chelation therapy can be used to dissolve the
dysprosium phosphate reaction product in vitro in <2 h. The
dysprosium phosphate reaction product which formed in vivo in the joint of a Sprague-Dawley rat was also dissolved by
EDTA chelation therapy in <1 week, without causing any detectable joint damage. The combination of DyLB glass
microspheres and
EDTA chelation therapy provides a unique "tool" for the medical community because it can deliver a large dose (>100 Gy) of localized beta radiation to a treatment site within the body, followed by complete biodegradability.