Selenium-doped calcium phosphate biomineral reverses multidrug resistance to enhance bone tumor chemotherapy.

The construction of a functional drug delivery system to reverse the multidrug resistance (MDR) of bone tumors in cases of failed chemotherapy remains a challenge. Herein, we demonstrate a selenium-doped calcium phosphate (Se-CaP) biomineral with high biocompatibility, biodegradability and pH-sensitive drug release properties. Se-CaP may not only serve as an effective drug-carrier to enhance the uptake of doxorubicin (DOX), but may also synchronously induce caspases-mediated apoptosis of osteosarcoma by generating intracellular reactive oxygen species (ROS). Furthermore, in vitro and in vivo studies obviously demonstrate that Se-CaP can reverse the MDR of osteosarcoma by down-regulating the expression of MDR-related ABC (ATP binding cassette) transporters proteins (ABCB1 and ABCC1). Finally, DOX-loaded Se-CaP can significantly inhibit DOX-resistant MG63 (MG63/DXR) tumor growth in nude mice. Considering its biomimetic chemical properties, the Se-CaP biomineral, with the multiple functions mentioned above, could be a promising candidate for treating bone tumors with MDR characteristics.