Preparation And Mechanical Properties Of High Porosity PCL/PLA Porous Scaffolds Based On Supercritical CO₂ Foaming Process

The preparation of tissue engineering scaffolds is the focus and difficulty in the field of biological tissue engineering.Scaffold materials are required to be biocompatible and biodegradable.Polylactic acid(PLA)and polycaprolactone(PCL)are FDA-approved biomaterials that can be implanted into the human body.They have renewable plant-derived,bio-phases,Capacitive and biodegradable.PLA has a hard and brittle character,and PCL has soft and tough properties.The blending of the two materials enables the two materials to complement each other in performance.The ideal tissue engineering scaffold should have a three-dimensional porous structure with interconnected porous structures to facilitate cell migration and growth on the scaffold.Supercritical CO2(SCCO2)foaming is a non-polluting,low-energy processing technology for preparing porous materials.In this paper,PCL/PLA blends were used as materials,and supercritical CO2 foaming was used as a technical means to study the relationship between condition-cell structure and mechanical properties.To provide theoretical basis and data support for the research and development of vascular tissue engineering scaffold preparation technology.The main research contents of the full text are as follows:1.Preparation of high open porosity PCL/PLA porous scaffold and regulation of cell structure.PCL and PLA biomaterials were blended at a ratio of 70/30.Based on the intermittent foaming technique,the effects of saturation time,saturation temperature and saturation pressure on the cell structure of microfoamed materials were analyzed by single factor experiment.The results show that the cell size decreases with the increase of saturation time and saturation pressure,and the cell density increases.With the increase of saturation temperature,the cell size increases and the cell density decreases.Since the blend is composed of two incompatible polymers,the study of the opening mechanism shows that the obtained foamed material has an internal open pore structure and the highest open porosity is over 90%.In addition,the surface of the obtained foamed sample is an open-cell structure,and the opening pattern is similar to the cross-sectional cell structure.2.Effects of thermal treatment on morphology regulation and foam structure of PCL/PLA blends.the optimal process was used to study the effect of thermal treatment on the foaming behavior.This chapter uses a different time and temperature to thermal treatment the sample first,followed by an optimum process for intermittent foaming.The results show that thermal treatment has no significant effect on the crystallinity and crystal form of PCL and PLA.However,as the thermal treatment time and temperature increase,the interface between the two phases is gradually blurred.At the same temperature,the average diameter of the cell is increased from 32.57±0.23?m to 46.35±0.36?m with the increase of thermal treatment time;at the same time,with thermal treatment the increase in temperature increases the average diameter of the cells from 32.57±0.23?m to 50.90±0.25?m.However,its porosity is maintained at around 90%regardless of annealing time and temperature.3.Preparation and mechanical properties of PCL/PLA small-diameter porous tubular scaffolds.This chapter is based on PCL/PLA as a blend material and uses a supercritical intermittent foaming technique to prepare a small-diameter porous tubular stent.The effect of the restricted wall thickness on the opening ratio of the small-diameter porous scaffold was studied.The results showed that the wall thickness increased from 220?m to 500?m and the opening cell content increased by 30%.Secondly,the effects of saturation pressure and saturation temperature on cell structure and open cell content were studied.The results show that the cell foam structure and cell open cell content change under constant conditions are consistent with free foaming.The inner and outer surfaces of the small-diameter porous tubular stent are open-cell structures.Finally,the mechanical properties of small-diameter porous tubular scaffolds under different processing conditions were studied,the longest rate is 179.8%,the stitching strength is 2.8N/needle,and the bursting pressure is up to 241KPa.This shows that the mechanical properties of the obtained small-diameter tubular stent can meet the requirements of the vascular stent.