Design And Functionalize Multilayers PU Scaffold For Cartilage Repair

Articular cartilage is a lack of blood vessels, lymphatic and nervous tissue,in the meanwhile proliferation ability of cartilage cells is extremely low.The dense cartilage matrix effects migration of cells to injure site which result in prohibiting self-repairing of cartilage.Methods of treatment of articular cartilage defects can be clasified into following categories,joint cleaning operations, Periosteal and periosteum transplantation, Autologous cartilage cells seeding and osteochondral transplantation.With the rapid development of medical practice,the treatment methods discribed above highlight enormously kinds of problems which pose restrictions on wide application of the methods.Moreover the heterogeneity structure of cartilage,which consist of calcified layer, radiation layer, transition layer and surface layer, determine concentration of each layer in order to achieve full-scale repair of articular cartilage.The emerging of tissue engineer offer us more flexible choices on repairing of cartilage through fabricating scaffold for each layer.As we all know, scaffold is especially important in tissue engineer as one of three basic elements. The adhesion, proliferation and differentiation of seed cells are vital to success of tissue engineer,and cell adhension on scaffold is the primary requirement to further proliferation and differentitation of cells.The hydrophilicity of material surface is crucial to adhension and spreading of cartilage cells.Nine groups of different hydrophilic of PCL-PEG-PCL triblock polymer have been synthesized based on different requrements of each defects layer.Molecular weight of polymers varies from 1500,2100 and 3000 dalton with the content of PEG ranging from 10% to 66.67%.The structure of triblock polymers are confirmed by 1H-NMR,FTIR and Raman spectrum.Moleclar weight of polymers are determined by 1H-NMR、GPC and the end group titration method. The hydrophilicity of polymers are detected by contact angle and water absorption test. Polyurethanes with different structure, different hydrophilic and soft and hard segments are synthesized by applying different soft segments. 1H-NMR,ATR-FTIR,GPC and XRD are used to assure structures of polyurethanes. Mechanical properties, hydrophilicity and degradation of polyurethanes are calculated,and mechanical behavior of polyurethanes are explained by combining XRD with DMA in microscopic scale.Different types of scaffold are fabricated by 3D-printing and thermally induced phase separation method.Scaffolds with diverse pore structures and diamters are obtained by changing process parameters. Optical microscope, scanning electron microscope and μ-CT are applied to scan and reconstructure scaffolds.Mechanical properties of scaffold prepared by thermally induced phase separation method are detected from static and dynamic mechanics aspects resulting better compression recovery capability.Tackled hydrophilic of scaffold,three drug delivery systems are designed to inspect controlling release abilities of resveratrol which is elected as model drug in order to meet demands of functionalizing scaffolds.It turns out that both microsphere and hydrogel DDS have unideal performance except microsphere/hydrogel composite DDS which can achieve nearly zero-order release.