Preparation And Properties Of Hydrogel Scaafolds With Clustered And Oriented Microstructure

With the continuous progress of cell biology and materials science,the emergence of tissue engineering provides a new therapeutic strategy for the reconstitution of lost or damaged organs and tissues.It is one of the important contents of tissue engineering research to provide tissue engineering scaffolds for cells to carry out life activities.Most biological tissues have hierarchical anisotropic structures generated by extracellular matrix components and cellular arrangements.The microstructure matching the damaged tissue structure can guide cell proliferation,alignment,and directional growth,which is beneficial to promote the generation of tissue and organ equivalents,or guide and enhance the recovery of damaged tissue structure and function.Therefore,it is critical to construct anisotropic scaffolds that are geometrically similar to the damaged tissue.Hydrogel scaffolds have broad application prospects in the field of tissue engineering due to their hydrophilic network structure,mechanical strength adapted to biological tissues,good biocompatibility and degradability.In this study,two polymers with good biocompatibility and degradability,polyvinyl alcohol(PVA)and sodium alginate(Alg),were used to develop PVA/Alg hydrogel scaffolds with anisotropic structure.By organically combining the directional freezing and drying under stretching methods,the prepared hydrogel scaffolds with clustered and oriented structure match the microstructure of damaged tissue,and can guide the cell arrangement and directional growth.Specifically,an anisotropic pore structure was formed inside the hydrogel through the directional freezing process,followed by drying the hydrogel under mechanical stretching.During the stretching process,the pore structure leads to inhomogeneous stress distribution,resulting in the formation of clustered and oriented microstructures,which further enhance the mechanical strength of the hydrogel.At the same time,calcium ions are cross-linked with the molecular chains of sodium alginate to form an "egg box" structure.The PVA/Alg hydrogel changed from a semi-interpenetrating double network to an interpenetrating double network structure,which greatly enhanced the mechanical strength of the hydrogel.Therefore,according to the requirements of different tissues for mechanical properties,the constructed anisotropic hydrogel has a wide adjustable range of Young’s modulus,and can be used for the culture of various cells such as chondrocytes and fibroblasts.In conclusion,PVA/Alg hydrogel scaffolds with clustered and oriented microstructure have tunable mechanical properties to match different biological tissues.The oriented structure of PVA/Alg hydrogel successfully guided the arrangement and directional growth of fibroblasts and chondrocytes.This work provides a new idea for the constructing hydrogel scaffolds with oriented microstructure,which has broad application prospects in the field of tissue engineering.