Cisplatin-functionalized dual-functional bone substitute granules for bone defect treatment after bone tumor resection

Invasive bone tumors pose a significant healthcare challenge, often requiring systemic chemotherapy and limb salvage surgery. However, these strategies are hampered by severe side effects, complex post-resection bone defects, and high local recurrence rates. To address this, we developed dual-functional bone substitute biomaterials by functionalizing commercially available bone substitute granules (Bio-Oss (R) and MBCP (R)+) with the established anticancer agent cisplatin. Physicochemical characterization revealed that Bio-Oss (R) granules possess a higher surface area and lower crystallinity compared to MBCP (R)+ granules, which enhances their capacity for cisplatin adsorption and release. In co-cultures with metastatic breast and prostate cancer cells (MDA-MB-231 and PC3) and bone marrow stromal cells (hBMSCs), cisplatin-functionalized granules and their releasates exhibited dose-dependent cytotoxic effects on cancer cells while having less impact on hBMSCs. Furthermore, investigations on the mechanism of action indicated that cisplatin induced significant cell cycle arrest and apoptosis in MDA-MB-231 and PC3 cells, contrasting with minimal effects on hBMSCs. In a rat femoral condyle defect model, cisplatin-functionalized granules did not evoke adverse effects on bone tissue ingrowth or new bone formation. Importantly, local application of cisplatin-functionalized granules resulted in negligible cisplatin accumulation without signs of apoptotic damage in kidneys and livers. Taken together, we here provide hard evidence that cisplatin-functionalized granules maintain a favorable balance between biosafety, anticancer efficacy, and bone regenerative capacity. Consequently, loading granular bone substitutes with cisplatin holds promise for local treatment of bone defects following bone tumor resections, presenting a safe and potentially more effective alternative to systemic cisplatin administration. Statement of Significance: Current treatments in combating malignant bone tumors are hampered by severe side effects, high local tumor recurrence, and complex bone defects after surgery. This study explores a facile manufacturing method to render two types of commercially available bone substitute granules (Bio-Oss (R) and MBCP (R)+) suitable for local delivery of cisplatin. The use of cisplatin-functionalized granules has shown promising results both in killing cancer cells in a dose-dependent manner and in aiding bone regeneration. Importantly, this local treatment strategy avoids the systemic toxicity associated with traditional chemotherapy to excretory organs. This dual-functional strategy represents a significant advancement in bone cancer treatment, offering a safe and more efficient alternative that could improve outcomes for patients following bone tumor resection.