Study On Fabrication And Cell Morphology And Structure Of Polylactid Acid Scaffold Matrices

Fabrication of tissue engineering scaffolds is a critical component in tissue engineeringfield and faces many research challenges. In the current research, various techniquesincluding elongational plasticizing, supercritical carbon dioxide (CO2) foaming, particulateleaching, were combined to develop novel biodegradable polymeric scaffold fabricationmethod. The structure development of the fabricated novel biodegradable polymericscaffold was investigated in this study as well as its biocompatibility.Material selection is an important step in porous scaffold preparation. Polylactic acid(PLA) is an important biodegradable polymer which possesses excellent mechanicalstrength, biocompatibility and biodegradability. It has become the most widely usedsynthetic material in tissue engineering field. Therefore, PLA was used in this research tofabricate porous scaffolds via different methods. The relationship among processingtechnique, scaffold structure and cell compatibility to the scaffold was investigated in detail.The PLA scaffolds with high porosity and pore interconnectivity could be prepared bycontrolling the pore microstructure. This research aspect is meaningful for developing no velefficient scaffold fabrication method and the fundamental theoretical study.In this research, traditional continuous extrusion foaming and batch foaming methodshave been used in PLA scaffold preparation by combining melt blending, gas foaming andparticulate leaching. This approach avoided the use of organic solvent. The effect ofprocessing conditions and the employment of porogens on the structure of PLA scaffoldswere studied and it was found that continuous extrusion foaming could mass produceporous PLA material, while the technique is complicated, the production is not constant andthe porosity and interconnectivity of the PLA scaffolds were low. However, batch foamingprocess is more simple and stable than extrusion foaming, and the structure o f the scaffoldsprepared could be manipulated easily by adjusting processing conditions and porogens. PLAscaffolds with bi-modal porous structure could be achieved via this approach.Combined porogens were used in scaffold preparation in order to obtain scaffolds with high porosity and high pore interconnectivity since it is hard to achieve with single porogen.Polyethylene glycol (PEG) and poly vinyl alcohol (PVA) were used as the secondaryporogen and their effects on the foaming behavior of PLA were investigated. The resultssuggested that the PEG crystals would change the system viscoelastic properties and causethe rupture of pores during foaming process, which improved the pore interconnectivity.Moreover, the excellent hydrophilicity of PEG could help improve the hydrohilicity ofscaffolds and further enhance cell adhesion. When PVA and sodium chloride (NaCl) wereused as porogens in PLA foaming, the scaffolds prepared have big pores caused by NaClparticles, small pores caused by foaming process and tiny pores resulted by PVA crystals.This complex porous structure could improve the scaffold porosity and poreinterconnectivity significantly. It was proven in these researches that the use of combinedporogens is an effective method to manipulate the porous structure of scaffold.Elongational technique was used in this research to solve the problem that traditionalmelt compounding could not achieve high porogen proportion. This technique allowed toprepare PLA/NaCl/PEG compounds with super high porogen loading and excellentdispersion. High porosity PLA scaffolds were prepared via subsequent batch foaming andparticulate leaching. The results suggested that the PLA scaffolds prepared by elongationaltechnique have high porosity, pore interconnectivity, and multiple size pore structure. Theideal scaffolds have93%porosity and96%pore interconnectivity.The biocompatibility of the scaffolds prepared via different methods was verified by invitro cell culture. The results revealed that the pore structure of the PLA scaffolds affectedthat cell behavior. The PLA scaffolds prepared using PEG/NaCl as porogens viaelongational plasticizing technique, supercritical CO2foaming and particulate leachingshowed promising cell compatibility due to the enhanced porogen content, high porosity,pore interconnectiviety and multiple pore size structure of the scaffolds.