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Peptide-based hydrogels are widely studied and applied in bone repair because of their good biocompatibility, biodegradability and designability. Peptide-based hydrogels can be endowed with different properties by introducing biologically functional groups into the peptide chain and adjusting the composition of the peptide-based hydrogels. In addition, in combination with growth factors, cells, and other scaffold materials, the peptide-based hydrogels can meet the needs of bone repair under different conditions. Therefore, we first analyzed the expected properties of peptide-based hydrogels in bone repair and methods to obtain these properties. Then, we focused on the applications in bone repair, especially the repair scheme based on peptide-based hydrogels for different types of bone defects. Peptide-based hydrogels can be used alone to fill bone defects, playing a role in bone conduction. The peptide-based hydrogels can also be used as a sustained-release carrier for cells, drugs, and the like, to improve the microenvironment of local bone regeneration and enhance the bone regeneration capacity. In addition, peptide-based hydrogels can provide solutions for repairing large segmental and weight-bearing bone defects by incorporating other scaffold materials. This review will provide the theoretical basis and cutting-edge design strategies for peptide-based hydrogels to promote the repair of bone defects.

Osteoporosis leads to various complications, such as prosthesis loosening and periprosthetic fracture, after joint replacement. This is mainly due to the impaired osteogenesis and excessive osteoclastic activity in osteoporotic microenvironment, which leads to insufficient osseointegration between prostheses and host bone. In this study, a functional drug-releasing inorganic–organic bioactive interface was constructed, comprising inorganic three-dimensional (3D) printed porous titanium alloy interface and organic poloxamer 407 temperature-sensitive hydrogel loaded with a novel anti-osteoporosis drug (technetium methylenediphosphonate, 99Tc-MDP). The inorganic–organic bioactive interface showed good biocompatibility and exhibited a sustained release profile. This performance enhanced osteogenic differentiation, inhibited the expression of osteoclast-related genes and inhibited the osteoclastogenesis, as compared with traditional bisphosphonates (alendronate) in vitro. When implanted into the distal femoral defect using an osteoporotic rabbit model, the 99Tc-MDP-loaded bioactive interface exhibited the most stable osseointegration with native bone. Furthermore, the drug delivery system inhibited osteoclastic activity via regulation of the osteoprotegerin/receptor activator of NF-κB ligand (OPG/RANKL) signaling pathway, which significantly ameliorated the osteoporosis status to effectively prevent continuous bone destruction around the interface. This study has clinical significance, as it demonstrates that the 99Tc-MDP modified inorganic–organic interface serve as a novel artificial prosthetic interface for patients with poor osteogenesis.

Bone nonunion has become one of the most severe sequelae of fractures, infections, bone tumors, or revision arthroplasty owing to its high morbidity and disability rate. Recently, bone nonunion has received considerable attention from plastic surgeons. There are different treatment methods for nonunion depending on its classification according to the etiology and pathological types. Bone tissue engineering provides advanced platforms for the treatment of bone nonunion via the use of material scaffolds with sufficient mechanical strength. Meanwhile, it promotes bone regeneration and osseointegration by the addition of various growth factors or drugs. This review describes in detail the classification and leading causes of nonunion, as well as the clinical treatment methods and basic research progress, including the design of metal and bioactive material scaffolds. Future challenges in engineering, material science, and three-dimensional printing are also summarized. This article may provide new perspectives of the clinical translation for the treatment of bone nonunion by understanding the pathogenic mechanism and the rational application of bioactive scaffolds. Keywords: Material, Bone nonunion, Classification, Pathological feature, Treatment progress