1.Introduction
Over the past 100 years,the development of biodegradable materials has helped to advance innovation in tissue-engineering technology by making such materials more feasible,resulting in technological breakthroughs and new clinical applications[1,2].Classical tissue-engineering theory involves three elements:bio-logical materials,seed cells,and factors.Research progress sug-gests that biodegradable materials with low immunogenicity,high biodegradability,good biocompatibility,and favorable regen-eration microenvironments are of great significance[3].