The Preparation And Characterization Of Tissue Engineering Scaffolds Based On Poly (L-Glutamic Acid)

Cartilage tissue engineering provides a new way for the repairing of cartilagedefect. To research and develop biodegradable and compatible scaffolds with thecharacter of mimic the extacellular matrix has been an important direction of cartilagetissue engineering. Natural extacellular matrix is mainly composed by protein andpolysaccharide. Construct scaffolds based on protein and polysaccharide can mimicthe extracellular matrix. In this work, cartilage tissue engineering scaffolds based onpoly(L-glutamic acid)(PLGA) and chitosan (CS) is studied. PLGA is a syntheticpolyamino acid, which performance can be effectively controlled. It also can mimicthe protein composition of extracellular matrix. CS is a natural polysaccharide, hasexcellent biocompatibility, which can mimic the glycosaminoglycan component ofextracellular matrix. PLGA and CS can construct cartilage tissue engineeringscaffolds which can mimic extracellular matrix.The cell adhesion and proliferation properties of PLGA and its blockcopolymers are studied. PLGA, poly(ethylene glycol)-poly(L-glutamic acid)(PEG-PLGA) and poly(acrylic acid)-poly(L-glutamic acid)(PAA-PLGA) blockcopolymer are synthesized. Using layer by layer assembly technology,polyelectrolyte multilayers based on PLGA and its block copolymers are assembledwith CS on the surface of poly(lactic acid)(PLA). The hydrophilic of the PLA isimproved and the roughness is increased. Qualitative adhesion and quantitativegrowth of adipose stem cells on the PLGA and its block copolymer polyelectrolytemultilayer films are studied; the results show that the PLGA polyelectrolytemultilayer films can promote the adhesion and proliferation of cells on the surface ofthe PLA. PAA-PLGA polyelectrolyte multilayers can further improve the celladhesion of PLGA, but its cell proliferation capacity is slightly lower. PEG-PLGApolyelectrolyte multilayer film forms an anti-cell adhesion and proliferation of surface. These results suggest that PLGA has a role in promoting cell adhesion andproliferation. PLGA is an excellent tissue engineering material.Chemical cross-linking method is used to construct of PLGA/CS cross-linkingscaffolds. The effects of freezing temperature and solid content on pore structure ofthe PLGA/CS cross-linking scaffolds are studied. Under the condition of freezingtemperature of-24°C and solid content of2%, SEM analysis show that PLGA/CScross-linking scaffolds with large pore and good interconnection are obtained. Theeffects of amount of activating agent, solid content, components ratio to the porosity,swelling ratio and mechanical performances of PLGA/CS cross-linking scaffolds areresearched. The porosity of the scaffolds prepared by cross-linking is larger than90%.Electrostatic complex method is used to prepare PLGA/CS electrostatic complexscaffolds. The pore structure of PLGA/CS electrostatic complex prepared bydifferent freezing temperature and solid content are studied. SEM analysis show thatPLGA/CS electrostatic complex of freezing temperature of-24°C and solid contentof2%have large pore and good interconnection. The effects of solid content,components ratio to the porosity, swelling ratio and mechanical performances ofPLGA/CS electrostatic complex are researched. Furthermore, chemical groups, thesurface contact angle and structural model analysis of PLGA/CS electrostaticcomplex and cross-linking scaffolds are used to explain the difference between thestructure and properties. The results show that the PLGA/CS cross-linking scaffoldshave good mechanical properties. However, PLGA/CS electrostatic complexscaffolds have more active chemical groups, better hydrophilic, rougher surfacecomposed by polyelectrolyte complex.MTT cytotoxicity test and cell culture experiments in vitro study showed thatPLGA/CS scaffolds have good biocompatibility and without cytotoxicity. PLGA/CS electrostatic complex have better cell adhesion and proliferation. In vitro culture,rabbit adipose-derived stem cells can adhesion and proliferation on surface andinternal of the PLGA/CS electrostatic complex scaffold. The cell-PLGA/CSelectrostatic complex scaffold repair rabbit articular cartilage defects by autologoustransplantation. Repairing full thickness defects of rabbit knee non-weight-bearingarea by autologous transplantation, histology results show that the PLGA/CSelectrostatic complex scaffold is completely degraded, the defect has been repairedand bonded integrated with the perimeter normal cartilage tissue, which indicate thatthe PLGA/CS electrostatic complex scaffold is an ideal tissue engineering scaffoldfor articular cartilage repair and regeneration.Porogens are used to control the pore structures of PLGA/CS electrostaticcomplex scaffolds. Spherical and fiber-shaped pore structures of PLGA/CSelectrostatic complex scaffolds are formed by using PLA micro spheres and fiber asporogens. Dioxane is added to obtain PLGA/CS electrostatic complex scaffolds withporous pore wall. The porosity of PLGA/CS electrostatic complex scaffolds withspecial pore structure remain unchanged, the swelling ratio increased slightly, whilethe mechanical properties decreased. The adhesion and proliferation results showthat the spherical, fiber-shaped pore structure and pore with porous wall can affectcell adhesion and proliferation of adipose stem cells on the scaffolds, which can beused in the fields of mimic extracellular matrix structure.