Yttrium-Enriched Phosphate Glass-Ceramic Microspheres for Bone Cancer Radiotherapy Treatment

This study presents the development and characterization of high yttrium-content phosphate-based glass-ceramic microspheres for potential applications in bone cancer radiotherapy treatment. The microspheres produced via flame spheroidization, followed by sieving, revealed a lack of aggregation and a narrow size distribution (45-125 μm) achieved across different yttrium oxide to glass ratio samples. Energy dispersive X-ray (EDX) analysis showed a significant increase in yttrium content within the microspheres with increasing yttrium oxide to glass ratio samples, ranging from approximately 1-39 mol % for 10Y-50Y microspheres, respectively. Concurrently, a proportional decrease in the phosphate, calcium, and magnesium content was observed. Further EDX mapping showed a homogeneous distribution of all elements throughout the microspheres, indicating uniform composition. X-ray diffraction profiles confirmed the amorphous nature of the starting P40 glass microspheres, while yttrium-containing microspheres exhibited crystalline peaks corresponding to cubic and hexagonal Y₂O₃ and Y(PO₄) phases, indicating the formation of glass-ceramic materials. Ion release studies revealed the reduction of all ion release rates from yttrium-containing microspheres compared with P40 microspheres. The pH of the surrounding media was also stable at approximately pH 7 over time, highlighting the chemical durability of the microspheres' produced. In vitro cytocompatibility studies demonstrated that both indirect and direct cell culture methods showed favorable cellular responses. The metabolic and alkaline phosphatase activity assays indicated comparable or enhanced cell responses on yttrium-containing microspheres compared to the initial P40 glass microspheres. Overall, these findings showed that significantly high yttrium-content phosphate glass-ceramic microspheres could be produced as versatile biomaterials offering potential applications for combined bone cancer radiotherapy treatment and bone regeneration.