Chitosan Microspheres Incorporating Doxorubicin-Loaded Mesoporous Silica Nanoparticles as a Potential Multifunctional Platform for Postoperative Osteosarcoma Management.

Osteosarcoma remains a major clinical challenge owing to its high recurrence rate, metastatic potential, and the frequent need for postoperative bone reconstruction. Here, we report a multifunctional platform consisting of doxorubicin-loaded mesoporous silica nanoparticles (DOX@MSN) embedded within chitosan microspheres (DMCS). The DMCS microspheres, with diameters of 100-200 µm, were fabricated by emulsion crosslinking and achieved a DOX encapsulation efficiency of 71.82% and a drug loading content of 17.95%. The platform exhibited pH-responsive drug release, with markedly enhanced DOX release under mildly acidic conditions relevant to the tumor microenvironment. In vitro, DMCS demonstrated favorable hemostatic and antitumor effects, while DOX@MSN showed preferential uptake by K7M2-WT osteosarcoma cells compared with MC3T3-E1 preosteoblasts. In addition, MCS microspheres, used as the DOX-free analog of DMCS, promoted osteogenic differentiation of MC3T3-E1 cells, as evidenced by increased alkaline phosphatase activity, matrix mineralization, and upregulation of osteogenesis-related genes, including Runx2, Col1A1, OPN, and OCN. In vivo, the platform enabled rapid hemostasis, effective inhibition of residual osteosarcoma after resection, and enhanced bone regeneration. Given that this is, to the best of our knowledge, the first attempt to integrate these three key functions within a single postoperative osteosarcoma-oriented system, the primary objective of this proof-of-concept study was to establish clear evidence for each function individually. This work defines key design principles and a functional validation framework for the development of next-generation integrated platforms for postoperative osteosarcoma management.