ZIF-8-modified hydrogel sequentially delivers angiogenic and osteogenic growth factors to accelerate vascularized bone regeneration

To realize high-quality vascularized bone regeneration, we developed a multifunctional hydrogel (SHPP-ZB) by incorporating BMP-2@ZIF-8/PEG-NH₂ nanoparticles (NPs) into a sodium alginate/hydroxyapatite/polyvinyl alcohol hydrogel loaded with PDGF-BB, allowing for the sequential release of angiogenic and osteogenic growth factors (GFs) during bone repair. ZIF-8 served as a protective host for BMP-2 from degradation, ensuring high encapsulation efficiency and long-term bioactivity. The SHPP-ZB hydrogel exhibited enhanced mechanical strength and injectability, making it suitable for complex bone defects. It provided a swelling interface for tissue interlocking and the early release of Zn²⁺ and tannin acid (TA) to exert antioxidant and antibacterial effects, followed by the sequential release of angiogenic and osteogenic GFs to promote high-quality vascularized bone regeneration. In vitro experiments demonstrated the superior angiogenic and osteogenic properties of SHPP-ZB compared to other groups. In vivo experiments indicated that the sequential delivery of GFs via SHPP-ZB hydrogel could improve vascularized bone regeneration. Further, RNA sequencing analysis of regenerative bone tissue revealed that SHPP-ZB hydrogel promoted vascularized bone regeneration by regulating JUN, MAPK, Wnt, and calcium signaling pathways in vivo. This study presented a promising approach for efficient vascularized bone regeneration in large-scale bone defects.