Foaming Mechanisms And Behaviors Of PBAT And Its Blends As Fallopian Tube Scaffold

Tissue engineering has been widely used in the repair of various tissues and organs in the human body,but fallopian tube scaffold has not been fully studied.In view of the unique structure and repair requirements of the fallopian tube,the existing scaffolds have disadvantages,such as excessive rigidity,weak bacterial resistance,and insufficient degradability.Biodegradable polymers combine good biocompatibility and degradability.In addition,PBAT processes good flexibility.The supercritical CO2 foaming is safe and nontoxic.Aiming at the preparation of tissue engineering scaffold that can be implanted in the fallopian tube,this thesis focused on supercritical CO2 foaming with PBAT and its blends.Through the combination of theoretical and experimental approaches,the mechanisms of targeted control of cellular structure,and its relationships with mechanics,degradation and bacterial resistance were clarified.A scaffold with qualified structure and comprehensive performance was prepared.The main research contents include:(1)In the framework of the classical dynamic density functional theory at the molecular level,considering contributions of the interactions between CO2-CO2,CO2-PBAT,PBATPBAT and the chain conformation of PBAT to the free energy of the system,the corresponding free energy functional expression was constructed.In combination with dynamic equations,a theoretical model was established.The dissolution properties of CO2 in PBAT were studied,and the solubility of CO2 in PBAT,the expansion coefficient of PBAT,the interface structure and interfacial tension between CO2 and PBAT,the bubble nucleation energy barrier and critical radius were calculated.The equilibrium thermodynamics and nonequilibrium diffusions were coupled to predict the diffusion coefficient of CO2 in PBAT and the viscosity of PBAT.Through theoretical approaches,the mechanisms of dissolution,diffusion,bubble nucleation and growth of CO2 in the matrix of PBAT were revealed.The results were used to guide the experimental research.(2)Under the guidance of theory,supercritical CO2 foaming experiments with PBAT,PBAT/PHBV,PBAT/PLGA,PBAT/PBS,PBAT/PCL and PBAT/PLA were conducted.Relationships of foaming conditions,including temperature,pressure and depressurization rate,and cellular structures were clarified.Influences of viscoelasticity,crystallinity and compatibility of different blends to foaming behaviors were analyzed.The results revealed that the PBAT/PLGA blend had good foamability and reasonable cellular structure.Combined with its excellent biodegradability,it was selected as the matrix for the subsequent antibacterial foaming and verification in vivo.(3)Based on the mechanism of targeted control of cellular structure,PBAT/PLGA foams with different structures were prepared,and their mechanical properties and degradation rates were studied.The results showed that under the premise that the cellular structure did not collapse or shrink,high immersion temperature,low immersion pressure and low depressurization rate led to a cellular structure with large expansion ratio and cell diameter,and low cell density.The compression test proved that the compression modulus of the foam was positively correlated with the relative density.The in vitro degradation experiment proved that the degradation rate increased with the increasing amount of PLGA.Considering the requirements of fallopian tube scaffolds,120?,16MPa and 2MP/s with a PLGA amount of 25%were determined to be the optimum.(4)Through the quaternization reaction,a quaternary ammonium salt with good thermal stability and bacterial resistance,dimethyl-decyl-aminoethyl-ammonium bromide(QDED10),was prepared.Through melt blending,the QDED10 was introduced into the matrix for antibacterial functionalization.Through supercritical CO2 foaming,antibacterial PBAT/PLGA foams were prepared.The results showed that QDED10 acted as nucleation sites in the bubble nucleation process,increasing the cell density of the system while still maintaining the perfect bacterial resistance.Further studies found that when the QDED10 amount was 3%,the foam could inhibitted the growth of bacteria and maintained bacterial resistance within a 7-day dissolution test,which proved that the foam possessed good antibacterial property.(5)Through the animal experiment with a rabbit model,the supporting ability to the fallopian tube of the foam was verified in vivo.It was confirmed that the antibacterial PBAT/PLGA foam possessed suitable cellular structure and mechanical property,as well as excellent biodegradability,biocompatibility and bacterial resistance.The foam could achieve the support of ruptured fallopian tube,inhibit inflammation caused by fallopian tube adhesion,facilitate the repair of epithelial cell tissue.The result laid a solid foundation for the development of fallopian tube scaffold with application potentials.