Preparation And Charactiriazation Of Poly (Lactic-co-glycolic Acid) (Plga) Biomimetic Extracellur Matrices And The Interfacial Interaction Between PLGA And Protein

Tissue engineering is a newly interdiscipline subject, which converges fundamental principles and methods from engineering and life science. The purpose is to construct an implant with bioactivity in vitro and repair tissue defect and replace organ. Generally, the seed cells are cultivated and proliferated in vitro. And then the more cells and exogenous extracellular matrix (ECM) would be mixed at a ratio and finally formed cell-material composites which are implanted into the site of tissue or organ defect. Gradually, the biomaterials degrade in vivo and eventually break down. The implanted cells secreted more and more ECM, newly formed tissue which will take over the mechanical load and achieve repairing wound and reconstructing function. During this process, the biomaterials as scaffolds can provide not only favorable space for cell growth and metabolism, but better environment for forming neo-tissue and organ. So, the biomaterial scaffold is very important for tissue regeneration. The key of tissue engineering is to discover the appropriate exogenous biomaterials which can mimic the structure and function of natural ECM. To our knowledge, the 3D porous scaffolds made by the biodegradable and biocompatible materials can be used to exogenous ECM and promote cell adhesion, growth and proliferation, finally form neo-tissue and control cell phenotype.Perfect exogenous ECM which also called artificial ECM can mimic the structure and function of natural ECM, that is, biomimetic of biomaterials. It will become one of the important studies on tissue engineering scaffolds. From the point of view of mimic, the biodegradable and biocompatible polymer, PLGA was successfully electrospun and mimic ECM. Moreover, the incorporation of MWCNTs with the favorable biocompatibility greatly promoted the mechanical properties of the composites. The interaction of biomaterials and proteins is believed to significantly affect the cell adhesion and proliferation, so sum frequency generation (SFG) vibrational spectroscopy was also used to study the interaction at the interface of PLGA film and human serum albumin (HSA) solution.At first, the methods, principles, the effect of forming fibers and the application of electrospun nanofibers have been simply introduced. Then THF and DMF by the volume ratio of 3:1 were selected as solvents and the electrospun PLGA nanofibrous mats with biodegradability and biocompatibility were prepared. The effect of molecular weight (Mw), flow rate, voltage, and composition on the morphology of electrospun PLGA nanofibers has been studied systematically. It was found that at a constant condition, the changes of voltage and flow rate did not appreciably affect the morphology. However, the Mw and flow rate of PLGA predominantly determined the formation of bead structures. Uniform electrospun PLGA nanofibers with controllable diameters can be formed through optimization. Electrospun mats have much higher porosity due to large suface-to-volume ratio compared to solution casting films. Further, multi-walled carbon nanotubes can be incorporated into the PLGA nanofibers, significantly enhancing their tensile strength and elasticity without compromising the uniform morphology. So electrospun PLGA and PLGA/MWCNTs composite nanofibrous mats can become advanced materials as tissue engineering scaffolds. This is beneficial to the subsequent design of fibrous materials for biomedical applications.Electrospun PLGA/MWCNTs nanofibrous mats have excellent mechanical properties, so biocompatibility was studied about mats. Electrospun porous PLGA and PLGA-MWCNTs mats, macroporous PLGA and PLGA-MWCNTs solution casting films with pore diameters of 2μm and 7μm were fabricated using two different methods. By the SEM images and MTT experiments, cell viability studies on these two types of different scaffolds show that cell attachment and proliferation on all membranes are superior to that on the cover slips, and the incorporation of MWCNTs within the PLGA scaffolds prepared using both methods tends to significantly promote the fibroblast attachment, spreading and proliferation when compared with the respective pure porous PLGA fibrous mats and macroporous PLGA films. At longer culture times, electrospun PLGA/MWCNTs nanofibrous mats display better cell proliferation and growth than macroporous films with similar composition. So MWCNTs have excellent biodegradability and biocompatibility and can increase porosity of composite nanofibrous mats. The high surface area-to-volume ratio characteristics might allow them to be a better choice for tissue engineering scaffolds.Protein adsorption is the first reaction that occurs between a biomaterial and a biological system after it is implanted. Further biomaterial-body interactions, including cell adhesion, inflammation, and blood coagulation, are influenced or controlled by the nature of the initial protein adsorption. Therefore, whether an implant material will be accepted or rejected by the body (biocompatible or not) is largely determined by protein adsorption. So it is important for biomaterial design to study the interaction at the interface of PLGA/HSA. In this work, a surface sensitive technique—sum frequency generation (SFG) vibrational spectroscopy was used to compare the signal difference between PLGA multilayers and spin-coating films at air interface. After protein adsorption, AFM image showed uniformity on the surface of PLGA films. And the hydrophilicity was enhanced. In addition, at a selected PH and concentration, SFG has been successfully applied to compare the difference between physical adsorption and chemical coupling at solid/liquid interface. Through fitting and calculating, the orientation angle range (tilt and twist) of HSA at the PLGA/HSA interface can be obtained, which is very helpful to calculate the exact angle of HSA at the solid/liquid interface in future. In short, the research will provide the data and the base for electrospun PLGA nanofibrous mats to be selected as tissue engineering scaffold in clinic.