Microchannel networks within engineered 3D scaffold can allow nutrient exchange and rapid blood vessels formation. However, fabrication of a bone microenvironment‐mimicking scaffold with hierarchical micro/nanofibrous and microchannel structures is still a challenge. Herein, inspired by structural and functional cues of bone remodeling, a microchannel networks‐enriched nanofibrous scaffold by using 3D printing and thermally induced phase separation techniques, which can facilitate cells migration and nutrients transportation, is developed. The customizable vascular‐like structure of polycaprolactone within the nanofibrous gelatin‐silica scaffold is fabricated using 3D‐printed sacrificial templates, while dimethyloxalylglycine (DMOG)‐loaded mesoporous silica nanoparticles (MSNs) located on the scaffold surface and bone forming peptide‐1 (BFP)‐loaded MSNs embedded in the scaffold are implemented for sequential release of DMOG and BFP. The cell experiments show that dual‐drug delivery scaffold (DBM/GP) promotes angiogenesis by stimulating migration, tube formation, and angiogenesis‐related genes/protein expression of endothelial cells, and osteogenesis by promoting osteo‐related genes expression and mineral deposition of osteoblasts. Additionally, DBM/GP scaffold facilitates the angiogenic activity of osteoblasts by activating phosphatidylinositol 3‐kinase/protein kinase B/hypoxia inducible factor‐1α pathway. Furthermore, enhanced vascularization and bone regeneration of DBM/GP scaffold are demonstrated via subcutaneous and skull defect models. Overall, this study reveals that the bone microenvironment‐mimetic dual‐drug delivery scaffold provides a promising strategy for bone defects treatment.

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Enhancing osteogenesis by promoting neural network reconstruction and neuropeptide release is considered to be an attractive strategy for repairing of critical size bone defects. However, traumatic bone defects often activate the damaged sympathetic nervous system (SNS) in the defect area and release excessive catecholamine to hinder bone defect repair. Herein, a 3D printed scaffold loaded with the calcium channel blocker‐nifedipine is proposed to reduce the concentration of catecholamine present in the bone defect region and to accelerate bone healing. To this end, nifedipine‐loaded ethosome and laponite are added into a mixed solution containing sodium alginate, methacrylated gelatin, and bone mesenchymal stem cells (BMSCs) to prepare a cell‐laden scaffold using 3D bioprinting. The released nifedipine is able to close the calcium channels of nerve cells, thereby blocking sympathetic activation and ultimately inhibiting the release of catecholamine by sympathetic nerve cells, which further promotes the osteogenic differentiation and migration of BMSCs, inhibits osteoclastogenesis in vitro, and effectively improves bone regeneration in a rat critical‐size calvarial defect model. Therefore, the results suggest that sustained release of nifedipine from the scaffold can effectively block SNS activation, providing promising strategies for future treatment of bone defects.

Bone Repair Scaffolds In article 2200785 by Xiaojun Zhou, Chuanglong He, and co‐workers, a hydrogel scaffold containing nifedipine‐loaded ethosome and laponite is constructed using a 3D printing technique. The release of nifedipine from 3D printed hydrogel scaffolds can effectively block sympathetic activation for inhibiting catecholamine release and promoting osteogenesis, thereby accelerating bone healing.

The clinical treatment of infectious bone defects is difficult and time-consuming due to the coexistence of infection and bone defects, and the simultaneous control of infection and repair of bone defects is considered a promising therapy. In this study, a dual-drug delivery scaffold system was fabricated by the combination of a three-dimensional (3D) printed scaffold with hydrogel for infected bone defects repair. The 3D printed polycaprolactone scaffold was incorporated with biodegradable mesoporous silica nanoparticles containing the small molecular drug fingolimod (FTY720) to provide structural support and promote angiogenesis and osteogenesis. The vancomycin (Van)-loaded hydrogel was prepared from aldehyde hyaluronic acid (AHA) and carboxymethyl chitosan (NOCC) by the Schiff base reaction, which can fill the pores of the 3D-printed scaffold to produce a bifunctional composite scaffold. The in vitro results demonstrated that the composite scaffold had Van concentration-dependent antimicrobial properties. Furthermore, the FTY720-loaded composite scaffold demonstrated excellent biocompatibility, vascularization, and osteogenic ability in vitro. In the rat femoral defect model with bacterial infection, the dual-drug composite scaffold showed a better outcome in both infection control and bone regeneration compared to other groups. Therefore, the prepared bifunctional composite scaffold has potential application in the treatment of infected bone defects.