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Applications of Layer-by-layer Assembly Technique on Surface Engineering of Poly(D, L-lactic Acid) and Titanium

Author: HuYan
Tutor: CaiKaiYong；WangYuanLiang
School: Chongqing University
Course: Biomedical Engineering
Keywords: Layer-by-layer assembly technique Polylactic acid Titanium Gene activation of biological materials Nano - memory
CLC: R318.08
Type: PhD thesis
Year: 2011
Downloads: 117
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Abstract


The surface properties of biological materials for the regulation of the interactions between cells and materials, including cell adhesion, migration and differentiation and biological behavior has a crucial role in the surface of the biological material. In a sense, the biological material interface is a link between the material and life. How to biomaterial surfaces functionalized regulating cell physiological function, the study of biological material / design put forward higher requirements. With the development of biological materials, the design of new biomaterials is expected to have the ability to stimulate specific cell / gene response at the molecular level, to achieve the purpose of the interface regulate cell fate. In the past few decades, polylactic acid and titanium as the implant body, is widely used in clinical treatment. However, polylactic acid and titanium biocompatibility, lack of induction of tissue formation performance universal challenges facing its clinical application. Many factors such as infection, shift, foreign body reaction, the fibrous cyst and implant and bone tissue interface cell death may lead to implant failure. The problems based on polylactic acid and titanium, in order to achieve the biological behavior of the interface-control cells, inducing the repair of damaged tissue, and the urgent need to develop new research ideas and technical means. Layer-by-layer assembly technique (Layer-by-Layer assembly technique, LBL) self-assembly system form a multilayer film technology based on the electrostatic attraction is a simple and efficient to build biologically active surface. In this thesis, the layers of self-assembly technology and combined with gene release / treatment, polylactic acid and titanium surface to build the interface of the biological activity and cellular response storage system, the purpose is to improve the material interface cells induced performance, polylactic acid for the development of new and titanium bone implant the foundation. The main research contents and conclusions are as follows: 1. Layers of self-assembly technique polylactide surface constructed chitosan (Chi) / DNA multilayer structures, and DNA release model. Use infrared spectroscopy (FITR), X photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and contact angle measurement instrumentation levy multilayer film deposition process. The contact angle measurements: starting from the fifth floor, Chi / DNA layered structure began to form. XPS and AFM confirmed that the outermost component determines the chemical nature and the surface topology of the surface of the multilayer film. DNA release behavior shows that within 32 hours in the presence of lysozyme, DNA can be slowly released into the solution. 2 layers of self-assembly technology to build gene functionalized poly lactic surface regulation of cell-specific / non-specific transfection and Mechanism of. First Synthesis of three different polymers, i.e. galactosidase chitosan (galactosylated chitosan, GC), galactosidase polyethyleneimine (galactosylated polyethylenimine, GP), and cyclodextrin grafted polyethylene imine (cyclodextrin grafted polyethylenimine, PEI-CD). Layer self-assembly technique, three polymers as polycationic polylactide surface constructed of multilayer films containing plasmid DNA (pDNA). The contact angle measurements and atomic force microscopy characterization of the assembly process, the results of the GC / pDNA multilayers show that starting from the fourth layer complete monolayer formation. pDNA from PDLLA / PEI / (pDNA / GC) 5/pDNA multilayer film sustained release for more than 42 hours. GC / DNA multilayers modified PDLLA substrate conducive to cell growth, and galactose grafted chitosan or polyethylene imine cells through receptor-mediated endocytosis ways to improve the gene transfection efficiency to achieve interface mediated cell-specific genes in situ transfection. Meanwhile, PDLLA / (PEI-CD/pDNA) 6 multilayers also confirmed the feasibility of a non-cell-specific genes in situ interface regulation transfected. The TEM observation results showed that the anti-DNA enzyme material surface mediated gene in situ transfected mechanisms: accompanied by degradation of the multilayer structure film, the in situ formation of the composite particles of the plasmid DNA, cultured cells of the original film in the multilayer structure bit to devour the particles in situ gene transfection. 3. Layer self-assembly technique to build gene activation at the surface of the titanium material interface, the regulation of bone marrow mesenchymal stem cells (MSCs) in situ differentiation. In order to further study the interface regulate gene transfection mechanism constructed plasmid DNA / chitosan multilayer films in the surface of the titanium film layer self-assembly technique to study the behavior of bone marrow mesenchymal stem cell differentiation. Plasmid pEGFP-hBMP2 (pGB) to express green fluorescent protein (GFP) and bone morphogenetic protein of BMP2. With the degradation of the multilayer film, the composite particles of the plasmid DNA from the continuous formation of the multilayer film, thereby situ transfection of bone marrow mesenchymal stem cells. GFP, hBMP2 mRNA, the expression of alkaline phosphatase and osteocalcin confirmed the differentiation of bone marrow mesenchymal stem cells transfected into osteoblasts achieve gene activation titanium surface induced stem cells in situ differentiation. 4. Layer-by-layer assembly technique in the surface of the titanium material to build chitosan the silk fibroin multilayers investigated multilayer films on osteoblast growth behavior. Chitosan / silk fibroin, chitosan / polystyrene sulfonate class extracellular matrix multilayer structures built in the surface of the titanium film layer self-assembly technique. The contact angle results show that the the Chi / SF and Chi / PSS layered structure began to form from the fifth floor. XPS and AFM confirmed that the outermost component determines the chemical nature and the surface topology of the surface of the multilayer film. The proliferation of osteoblasts, the total content of a detection result of the activity of alkaline phosphatase expression and DNA showed that the multilayer film of Chi / SF and Chi / PSS coating a titanium film having a good biocompatibility, can promote bone formation. 5. Layers of self-assembled nano-memory technology built titanium surface, the regulation of bone homeostasis. Layers of self-assembly technology will be assembled drug-loaded mesoporous silica nanoparticles to the surface of the titanium material. Mesoporous silica as nano-memory storage β-estradiol. Mainly on the the titanium surface nano-memory assembly process and cell behavior in the biological response of the surface of the titanium. TGA analysis showed that β-estradiol may be supported by a simple diffusion equilibrium mesoporous silicon. Zeta potential test results show that the the MSN surface successfully constructed chitosan (Chi) / gelatin (Gel) multilayers E2 of-MSN _AT_ PEM. The scanning electron microscopy reflect the E2-MSN @ PEM nanoparticles were successfully assembled into the surface of the titanium film hormone function of titanium hybrid film modified titanium. ALP activity, mineralization ability and OPG, OPN mRNA expression to verify that the system has good cell compatibility and performance induced bone formation. The same time, the system has the ability to inhibit the expression of osteoclast function, and regulation as the dynamic balance of bone cells / osteoclasts, the bone implant treatment for osteoporosis patients to accept new ideas. 6. Layer self-assembly technique to build cytokine activation the TiO 2 nanotubes regulation of bone marrow mesenchymal stem cell migration and differentiation. Spin coating layer self-assembly techniques to build cells activated TiO 2 nanotubes. First TiO 2 nanotubes prepared by anodic oxidation method, as cytokines BMP2 nano-memory. The TiO 2 nanotube surface load BMP2 build chitosan (Chi) / gelatin (Gel), TiO 2 / BMP2/LBL. The results show that the use of scanning electron microscopy and contact angle the spin coating layer self-assembly technique in TiO 2 / BMP2 build protective layer Chi / Gel multilayers. SOD activity assay showed that SOD activity Chi / Gel multilayers can protect and prolong its life. With the other TiO 2 sample compared to TiO 2 / BMP2/LBL system more conducive to promoting the migration and differentiation of MSCs. 7. Layers of self-assembly technology to build bone cell regulation of the microenvironment of the bone marrow mesenchymal stem cell differentiation and promote bone formation in vivo. Layer self-assembly technique to build the osteoinductive properties of biological functions the multilayer film covering the TC4 implants, and TC4/LbL/BMP2/FN system. With degradation of the multilayer film of BMP2 long period of sustained release. ALP expression, cell mineralization and osteoblast gene (Runx2, Osterix, OCN, OPN, ALP and Col Ⅰ) test results show that the multi-layer film structure can promote vitro adhesion and differentiation of MSCs. Vivo Micro-CT and histological analysis that TC4/LbL/BMP2/FN implantation physical implant / native bone interface effectively induce new bone formation.

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CLC: > Medicine, health > Basic Medical > Medical science in general > Biomedical Engineering > General issues > Biomaterial
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