Investigating the Effect of Dexamethasone Delivery on Osteogenic Differentiation of MC3T3-E1 Cells in a Mineralized Hydrogel Microenvironment

The current traditional approaches, such as autografts, allografts, and metal implants, for healing fractures with critical size defects have numerous disadvantages. These disadvantages highlight the necessity of bone tissue engineering (BTE) in modern times. The delivery of bioactive molecules offers several clear advantages for enhancing cellular functions during BTE. This study presents a BTE strategy by integrating a mineralized alginate hydrogel with the sustained release of dexamethasone (DEX). Nanohydroxyapatite (nHAp) was incorporated to create a mineralized microenvironment that enhances osteoconductivity, while poly(lactide-co-glycolide) (PLGA) microspheres (PLGA-MS) were used for the controlled delivery of DEX, ensuring continuous osteoinductive signaling. The physical characterization of the alginate hydrogel scaffold was performed, including swelling degree measurement, stability assessment using rheometric analysis, degradability, and evaluation of the porous surface structure using field emission scanning electron microscopy. The scaffold's surface area was estimated by Brunauer-Emmett-Teller (BET) analysis, and FTIR confirmed DEX incorporation into PLGA-MS. - To identify the optimal DEX concentration for promoting osteogenesis, 3D alginate hydrogel models were tested using 0.05, 0.1 and 1 mg/mL. Cell viability assay, alkaline phosphatase (ALP) activity, and DNA content were evaluated. The results indicated that 0.1 mg/mL DEX had the highest normalized ALP content and minimal cytotoxicity; hence, it was chosen for the next phase of this study. Further, an effective delivery system for DEX, utilized both direct and sustained release within mineralized alginate, was evaluated to assess its osteoinductive potential. The results of this study indicated that the sustained delivery of DEX was the most effective for BTE applications due to its high osteogenic potential, as evidenced by increased normalized ALP activity and enhanced bone mineralization, indicated by a higher calcium content. The drug release patterns were also studied, and the results showed a 72% cumulative release in the PLGA-DEX group after 14 days. The system utilized an injectable alginate hydrogel forminimally invasive delivery and employed a 3D culture model that more accurately replicates the <i>in vivo</i> bone environment compared to traditional 2D systems. This comprehensive approach achieved dual functionality by promoting osteogenesis while simultaneously providing anti-inflammatory effects, thereby addressing key challenges in bone repair and offering a promising solution for improved bone regeneration.