High-throughput design of 3D hybrid stem cell spheroids loaded with zinc-doped urchin-like hydroxyapatite and their osteopromotive bionics

Stem cell spheroids, as an advanced platform in cell therapy, have shown great potential for improving therapeutic efficacy through enhanced cell-cell and cell-microenvironment interactions. Meanwhile, zinc-based biomaterials are attracting increasing attention for their biological functions. However, their roles in modulating stem cell spheroids remain largely unclear. In this study, we successfully synthesized zinc-doped urchin-like hydroxyapatite (Zn-uHA) via a hydrothermal method and verified its long-term antibacterial activity. Utilizing microwell array technology, we conducted 3D cell culture of human dental pulp stem cells (hDPSCs) with Zn-uHA, thereby achieving high-throughput and precise fabrication of 3D hDPSCs/Zn-uHA hybrid stem cell spheroids. Compared with pure cell spheroids, hDPSCs/Zn3-uHA hybrid spheroids demonstrated significantly enhanced cell migration and osteogenic differentiation, with osteogenesis-related gene expression upregulated 2.7-fold. In vivo studies further confirmed that the hybrid cell spheroids exhibited favorable biocompatibility, with no evident inflammatory response or immune rejection, and enabled prolonged retention at the implantation site. Additionally, they significantly promoted neovascularization and new bone formation. These findings suggest that Zn-uHA-integrated stem cell spheroids represent a promising strategy for enhancing both antibacterial and osteogenic performance, offering potential applications in bone tissue engineering, particularly in infection-prone clinical scenarios such as orthopedics and dentistry.