Microsphere-Mediated Sustained Delivery of Growth Factors Stimulates Osteogenesis in Target Cells in a Three-Dimensional Microenvironment

Abstract

Efficient bone repair relies on both osteogenic and angiogenic signals, with growth factors playing a pivotal role. Despite decades of recognition of their therapeutic potential, the optimal dosages and delivery routes of growth factors still require extensive investigation. Previous research demonstrated the osteoinductive and angiogenic potential of growth factors. However, effective therapeutic outcomes depend on precise dosing and prolonged delivery. This study investigates the dual delivery of key growth factors, bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF), providing insights into their optimal dosages and delivery mechanisms. The combination of these growth factors may enhance scaffold-mediated bone regeneration in the early stages of healing. This study employed a dual delivery system using BMP-2 and VEGF, comparing two methods to determine the optimal dosage and delivery strategy. The combined effect indicates that sustained delivery is a more efficient method. Osteogenesis and angiogenesis were examined in an interpenetrating network (IPN) hydrogel composed of alginate and polyethylene diacrylate (PEGDA), which encapsulated preosteoblast MC3T3 cells. The findings of this study reveal significant increases in alkaline phosphatase (ALP) activity and calcium content, emphasizing the effectiveness of this approach. Biomaterial characterization, including swelling measurements, Fourier transform infrared (FTIR) spectroscopy, confirmed growth factor encapsulation, and a release assay validated the delivery process. Compared to direct delivery, sustained delivery increased ALP activity and calcium release by up to 1.12- and 1.85-fold, respectively. Molecular studies indicated that sustained delivery of both growth factors had a stronger osteoinductive and angiogenic effect than direct delivery. This research evaluates the effects of growth factor delivery in a 3D hydrogel-based microenvironment using hydrogels and compares delivery methods to identify a more effective strategy for bone healing.

Keywords: angiogenesis; bone morphogenetic protein‐2 (BMP‐2); growth factors; osteogenesis; vascular endothelial growth factor (VEGF).