Multifunctional biodegradable mesoporous microspheres of Eu³⁺-doped amorphous calcium phosphate: microwave-assisted preparation, pH-sensitive drug release, and bioimaging application

Biodegradable inorganic mesoporous materials hold promise for various biomedical applications such as drug/gene delivery, bioimaging, and photodynamic/photothermal and ultrasound therapy. Herein, multifunctional mesoporous microspheres of europium-doped amorphous calcium phosphate (Eu³⁺-doped ACP) have been prepared using a natural biomolecule adenosine triphosphate (ATP) by the rapid microwave-assisted solvothermal method. This method has advantages such as surfactant-free, rapid and energy-saving. The ATP molecule plays key roles as a phosphate source and a structure mediator. Furthermore, the Eu³⁺-doped ACP mesoporous microspheres exhibit advantages such as high specific surface area (from 253 to 315 m² g^-1), high biocompatibility, pH-responsive drug release, and in vitro/in vivo fluorescence imaging properties. The mechanism of pH-responsive drug release can be explained by the degradation of ACP mesoporous microspheres at low pH. The docetaxel-loaded Eu³⁺-doped ACP mesoporous microspheres showed good anticancer performance in vitro. The as-prepared Eu³⁺-doped ACP mesoporous microspheres are promising for applications in drug delivery, tissue engineering, bioimaging, etc.