Luminescent net-like inorganic scaffolds with europium-doped hydroxyapatite for enhanced bone reconstruction

Bone reconstruction is an urgent problem during clinical treatment. In the past few decades, the construction of composite scaffolds has been a hot spot in the research field of bone tissue engineering (BTE). However, the disadvantages of composite materials raise our awareness to explore the potential application of hydroxyapatite (HAp) in bone substitutes due to the closest properties of HAp to natural bone tissue. In our study, we synthesized Eu³⁺-doped HAp (HAp:Eu³⁺) ultralong nanowires, which can be transformed to hydrophilic net-like scaffolds via a thiol-ene click reaction. The property of luminescence of HAp from Eu³⁺ is beneficial for identifying the relative position of materials and bone marrow mesenchymal stem cells (BMSCs). HAp:Eu³⁺ scaffolds with excellent cell biocompatibility could promote the expression of early bone formation markers (ALP and ARS) and enhance the expression of genes and proteins associated with osteogenesis (Runx 2, OCN, and OPN). In the end, the results of the in vivo osteogenesis experiment showed that pure HAp scaffolds presented different effects of bone tissue reconstruction compared with the composite scaffolds with HAp nanorods and polymer materials. The superior osteogenic effect could be observed in net-like pure HAp scaffold groups. Furthermore, the absorption of HAp:Eu³⁺ scaffolds could be monitored due to the luminescence property of Eu³⁺. This strategy based on ultralong HAp nanowires proved to be a new method for the construction of simple reticular scaffolds for potential osteogenic applications.