Biomimetic Hydrogels Loaded with Nanofibers Mediate Sustained Release of pDNA and Promote In Situ Bone Regeneration.

Polymer hydrogels are generally insufficient biomechanics, strong resistance to cell adhesion, and weak bioactivity which limits their application in bone tissue engineering considerably. In order to develop a bone tissue engineering material with both good mechanical properties, osteogenic and angiogenic activity. Nanofibers carrying DNA plasmid (pNF) are introduced to gelatin methacryloyl (GelMA) and thiolated chitosan (TCS) system for preparing a novel GelMA/TCS/pNF composite hydrogel with dual network structure. By characterization of the compressive measurements, the resulting composite scaffold shows greatly enhanced mechanical strength (0.53 MPa) and is not damaged after 20 cycles of compression. And the fabricated composite scaffold displays sustained release of bone morphogenetic protein-2 that can induce osteogenic differentiation and angiopoietin-1 that promotes vascularization. The cell experiment shows that this system can significantly promote MC3T3-E1 cell attachment, proliferation, as well as osteogenic-related and angiogenic-related genes expression of MC3T3-E1 cells. Moreover, the in vivo results show that the composite scaffold with activated gene fibers can significantly promote osteogenesis and vascularization leading to favorable capacity of bone regeneration, meaning that the resulting biomimetic composite hydrogel scaffolds are excellent candidates for bone repair materials.

Stress-relaxing double-network hydrogel for chondrogenic differentiation of stem cells.

The mechanical environment of extracellular matrix (ECM) plays an important role in adjusting the behaviors of cells. Natural ECM are highly viscoelastic materials with stress-relaxion behavior. Hydrogel is considered as a promising and attractive material for cell carrier, but they are typically elastic serving as synthetic ECM. Double-network (DN) hydrogel has an interpenetrating network of special structure combining the advantages of both rigid and ductile components, due to which the mechanical properties of the system can be very different from that of the single-network ones, and some special biological properties can be obtained. In this study, GG/PEGDA DN hydrogel was prepared by combining gellan gum (GG) with polyethylene glycol diacrylate (PEGDA), and then the influence of the two individual networks on the viscoelasticity of the system were investigated. Furthermore, the effects of viscoelasticity of GG/PEGDA DN hydrogel on the biological behavior of bone mesenchymal stem cells (BMSCs) were explored in vitro and in vivo. The results indicate that the spreading of BMSCs was closely related to the relaxation behavior of the hydrogels. GG/PEGDA DN hydrogel shows excellent mechanical and relaxation properties which provide a favorable physical environment for cell proliferation and spreading, and induce chondrogenic differentiation. Our study demonstrates that this DN hydrogel has bright prospects in the fields of cell carrier and cartilage tissue engineering.