Europium-doped hybrid nano-complexes: a potential strategy for metastasis prevention in osteosarcoma

Metastasis is a major issue in cancer therapy, resulting in poor prognosis and death. However, there is currently no widely established prophylactic strategy for early metastasis in the clinical setting. Although water-soluble EuCl₃·6H₂O has the potential to exhibit a metastasis-inhibiting effect similar to migrastatics and matrix metalloproteinase inhibitors (MMPIs), intravenous administration of europium (Eu)-containing compound solution may not efficiently accumulate Eu ions in tumors and could be rapidly cleared from the body. In this study, we developed Eu ion-doped superparamagnetic iron oxides incorporated into bovine serum albumin hybrid nano-complexes (Eu:SPIO@BSA nano-complexes) to enhance tumor accumulation and prevent metastatic osteosarcoma via intravenous administration. In vitro studies showed that Eu:SPIO@BSA nano-complexes had a migration-inhibiting effect and affected pseudopodia formation in K7M2 cells. In vivo studies showed that distant lung metastasis was inhibited by the magnetism-enhanced targeted delivery of Eu:SPIO@BSA nano-complexes. Taken together, our results provide evidences that the Eu:SPIO@BSA nano-complex, with precise delivery, higher hemocompatibility and low liver toxicity, is a potential candidate for improving the therapeutic efficacy of metastasis prevention in osteosarcoma.