Study On The Preparation Of High-porosity Hydrophilic Polylactic Acid Porous Scaffold Based On Supercritical CO₂ Foaming Process

The preparation of tissue engineering three-dimensional porous scaffold is one of the key technologies in tissue engineering,and the use of biodegradable polymers to prepare tissue engineering porous scaffold is an important research direction in the field of tissue engineering scaffold preparation.Polylactic acid is widely used in the field of tissue engineering scaffolds due to its degradability and biocompatibility.However,the connectivity between the pores of PLA-based tissue engineering porous scaffolds is low and the hydrophilicity is poor,which greatly limits the adhesion and growth of cells or tissues on such tissue engineering porous scaffolds.At present,there are many studies on the preparation of microporous materials by supercritical carbon dioxide foaming,and the research on the preparation of tissue engineering porous scaffolds by supercritical carbon dioxide foaming is still in the development stage.In this paper,based on supercritical carbon dioxide foaming technology,biocompatible low-melting aliphatic polyester polybutylene succinate and water-soluble polymer polyethylene glycol are melted together with PLA matrix.By adjusting the foaming temperature and soaking pressure,the open rate of the cellular structure of the PLA three-dimensional porous scaffold can be improved to solve the problem that a single PLA component easily forms a closed-cell structure,and the addition of PEG can increase the hydrophilicity of the three-dimensional porous scaffold,Conducive to cell adhesion and growth.It is mainly divided into the following two parts:(1)Pure PLA,PLA/PBS/PEG ternary blending system with different proportions were prepared by melt blending.The impact strength of PBS and PEG on the toughness of the blend was investigated by impact strength;the effect of the content of PBS and PEG on the rheological behavior of the blend system was investigated by rotational rheology;the content of PBS and PEG on the blend was investigated by scanning electron microscopy The influence of the microscopic morphology and phase morphology of the mixed system;the effect of the content of PBS and PEG on the hydrophilicity of the blend was studied by measuring the contact angle.The research shows that with the increase of the content of PBS and PEG,the toughness of the PLA/PBS/PEG blending system is significantly improved,the complex viscosity of the PLA/PBS/PEG blending system is greatly reduced,and the PLA/PBS/PEG compound The hydrophilicity of the material is significantly improved.The addition of PEG can improve the compatibility of PBS and PLA,reduce the dispersion size of PBS in PLA matrix,and increase the dispersion density.(2)PLA/PBS/PEG blend porous foaming material was prepared by supercritical carbon dioxide intermittent foaming method.The effects of foaming temperature andimmersion pressure on the microcellular structure of porous foamed samples were studied,and the best foaming process conditions were explored.By analyzing the statistical data such as cell size,cell density,and cell opening rate of foam samples with different composition ratios under the same process conditions,the factors that affect the cell opening rate of PLA-based foam samples are explored.The results show that the optimal foaming process conditions are: foaming temperature 100 ?,immersion pressure 16 MPa,immersion time 1 h;with the increase of PEG content,the open porosity of the foamed sample increases and the expansion ratio decreases,when the PEG content After more than 10%,the melt strength of the system decreases,the cell structure is prone to collapse,and the open cell rate decreases.When the PLA/PBS/PEG ratio is 90/10/10,the foamed sample has a higher open cell ratio and a uniform cell structure.(3)By combining the micro-phase morphology distribution and rheological behavior of the PLA/PBS/PEG blend system with the micro-cell structure and open porosity of the foamed sample,PLA/PBS/PEG high open porosity is proposed Opening mechanism of tissue engineering scaffold.The addition of PEG can improve the compatibility of the PLA/PBS incompatible system,reduce the dispersion size of the PBS phase in the PLA matrix,increase the dispersion density,expand the two-phase interface,and provide more nucleation for heterogeneous nucleation Location.At the same time,the plasticizing effect of PEG on PLA reduces the melt viscosity of the entire system,prompting more cells to grow to the PLA/PEG matrix,thereby increasing the probability of the formation of open cells.