Dysprosium lithium borate glass mircrospheres for radiation synovectomy: The in vitro and in vivo performance evaluation

The radioactive dysprosium lithium borate glass (DyLB) microspheres with different glass compositions were prepared for radiation synovectomy. The biodegradability and biocompatibility of these DyLB microspheres were evaluated in vitro and in vivo. The DyLB microspheres studied in this work were partially biodegradable in a simulated body fluid (SBF), with the final weight loss of the microspheres in the range of 24.6% and 55.0% (wt.%) after 8days of immersion. The ICP results revealed that the dissolution of lithium significantly decreased from 100% to 53.7% with increasing content of Dy2O3 in the microspheres from 18% to 22% (wt.%, from S-1 to S-3). However, for all of the three samples, nearly all of the dysprosium (>99.997%, wt.%) remained in the microspheres, in the form of insoluble phosphates and carbonates, which was proved by the SEM and EDX analyses. The degradation of DyLB microspheres in SBF gradually decreased with immersion time and eventually reached equilibrium after 7days of immersion. Compared to the other two samples, the S-3 sample with the lowest Dy3+ dissolution (about 0.002%) was considered more secure for clinical application. Furthermore, the S-3 DyLB microspheres exhibited good biocompatibility, since neither tissue damage nor inflammation was observed, after they were implanted in the liver of rat for two weeks. After neutron activation, the radionuclide purity of radioactive S-3 DyLB microspheres was 99.999%, which were suitable for radiation synovectomy.