Preparation of Aspirin Polymer Nanoparticle Prodrugsand Their Promotion of Osteogenic Differentiation in DPSCs

Dental pulp stem cells (DPSCs) are among the most widely used and readily accessible mesenchymal stem cells, exhibiting strong proliferative and osteogenic differentiation capabilities. Multiple studies have demonstrated that aspirin promotes the osteogenic differentiation of mesenchymal stem cells, making it a viable active agent in bone tissue engineering. However, its poor water solubility and concentration-dependent osteogenic effects limit its further application. Polymer-drug conjugates (PDCs) represent a drug delivery strategy where active pharmaceutical ingredients are chemically covalently linked to polymers. Under specific conditions (e.g., light exposure, pH changes, ROS, GSH, enzymes), these conjugates degrade, releasing the active drug. We conjugated aspirin (AS) to a polymer, which self-assembled into nanoscale polymer particles (ASNPs) in aqueous solution. This enhanced AS bioavailability and achieved sustained-release effects. We evaluated the in vitro osteogenic differentiation promotion of ASNPs on dental pulp stem cells (DPSCs) and investigated whether combining ASNPs with DPSCs could achieve superior bone defect repair in a rat cranial defect model. Biocompatibility of AS and ASNPs was assessed via CCK-8 assay and vital/necrotic staining. Optimal osteogenic concentrations of aspirin for DPSCs were determined through alkaline phosphatase (ALP) staining and alizarin red staining. ASNPs' effects on DPSC osteogenesis were evaluated using ALP staining with quantitative analysis, alizarin red mineralization staining with semi-quantitative assessment, and real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot studies. Finally, a rat cranial defect model was employed, with new bone formation analyzed via micro-CT scanning. RT-qPCR), and Western blot analysis to investigate the in vitro osteogenic differentiation-promoting effects of ASNPs on DPSCs. Finally, using a rat cranial defect model, micro-CT scanning was employed to analyze new bone formation and validate the in vivo bone defect repair efficacy of ASNPs combined with DPSCs. Results indicate that ASNPs exhibit superior osteogenic induction of DPSCs compared to AS alone. The rat cranial defect model demonstrates that ASNPs combined with DPSCs achieve greater new bone formation at the defect site, yielding superior cranial defect repair outcomes. This approach holds promise for providing a more efficient and stable method for clinical bone defect repair.