Preparation Of Multifunctional Tissue Repair Scaffolds And Study On Their Biological Properties

The natural polymer-based tissue scaffolds are a kind of biomaterials with a three-dimensional network structure,which are formed by crosslinking or polymerization of natural biopolymers through various physical/chemical interactions.They have broad applications in the field of tissue repair because they have high water content,excellent biocompatibility,tissue affinity and can mimic the extracellular matrix microenvironment of the body tissues.However,the poor mechanical properties and limited functionality restrict the application of natural polymer-based tissue repair scaffolds in clinical tissue repair.Based on the natural biopolymer,functional nanoparticles and various techniques for improving the polymer network,the objective of this study is to prepare multi-functional tissue repair scaffolds with good mechanical properties to accelerate tissue regeneration and promote tissue defect repair.The research content includes the following two parts.?1?Near-infrared?NIR?light stimulation has the effects of reducing inflammatory reactions,accelerating tissue metabolism and promoting tissue regeneration.It is very vital to design and prepare materials with NIR responsiveness for skin tissue repair,which promote skin tissue regeneration with the assistance of NIR stimulation.In this study,polydopamine nanoparticles?PDA-NPs?with excellent NIR photothermal conversion ability were introduced into chitosan?CS?and silk fibroin?SF?complex network to construct PDA-NPs entangled CS/SF?PDA-NPs-CS/SF?composite scaffold.The introduction of PDA-NPs also endowed the composite scaffold a good NIR photothermal effect to efficiently convert NIR light into heat.In addition,PDA-NPs have abundant functional groups,which worked as bioactive sites to achieve effective immobilization and slow release of epidermal growth factor?EGF?.The full-thickness skin defect repair experiment demonstrated that the composite scaffold can respond to the external NIR stimulation and achieve NIR photo-thermotherapy,which accelerated the healing of skin defect.The introduction of EGF and NIR photo-thermotherapy produced a synergistic effect that further increased the wound healing rate.?2?Current natural polymer-based scaffolds are not fully satisfied the requirement of bone repair due to poor mechanical properties,and lack of antibacterial properties and osteoinductivity.This study developed tough and resilient chitosan?CS?and silk fibroin?SF?composite scaffold incorporated with multi-ions co-doped hydroxyapatite?HA?nanoparticles.Firstly,silver ions?Ag⁺?and strontium ions(Sr²⁺)co-doped HA nanoparticles?AgSrHA-NPs?were synthesized by hydrothermal method.Then,the composite scaffold was prepared by freeze-drying technology when AgSr HA-NPs were introduced into the CS/SF composite network.Finally,the composite scaffold was treated by a mixture solution of poly?ethylene glycol?diglycidyl ether?PEGDE?and NaOH at 60°C.NaOH treatment can induce the fold of chitosan chains to form the partial crystallized area,serving as the physical crosslinking points of composite networks.Under the alkali condition,the PEGDE can react with the CS and SF network to form chemical crosslinking points of composite networks.The mixture solution of PEGDE and NaOH treatment construct physio-chemical hybrid-crosslinking network in composite scaffold.which endowed the composite scaffold super resilience and flexibility.Furthermore,nano-reinforcement effect of AgSrHA-NPs further enhanced the mechanical properties of the composite scaffold.In addition,the slow release of Ag⁺and Sr²⁺from the composite scaffold endowed the composite scaffold with antibacterial properties and osteoinductivity for a long period of time,which can avoid both prevent microbial infection and promote bone regeneration during bone repair.In short,the AgSrHA/CS/SF composite scaffold with excellent mechanical properties and long-term effective dual-biofunction of antibacterial properties and osteoinductivity would be an ideal candidate for successful bone repair in clinics.