| Some biomedical devices, such as cardiovascular stents, artificial bone and biosensors, should be endowed some biofunctions by surface modification. Although widely applied in research, many surface modification techniques have some limitations including expensive instrumentation, complex procedures, specific requirement for reaction condition and substrate, and difficulty to obtain the required reagents. Moreover, although surface has been modified, it still exists some problems, such as a loss of biomolecule due to unstable structure, a single kind of biomolecule immobilization due to a single kind of reactive functional group, and cytotoxicity. Therefore, it is necessary to develop a new kind of surface modification technique which is cheap, simple, good biocompatible, nonselective for substrate, and has a variety kinds of reactive functional groups which can be used to immobilize different kinds of biomolecules for introducing multifunction. Our investigation was inspired by the formation mechanism of polydopamine coating, and the gallic acid containing three o-phenol groups and the hexamethelinediamine containing two primary amine groups were used to copolymerize and deposite GAHD film on several kinds of materials surface by acid-base reaction, Michael addition reaction and schiff base reaction. It was proved that the GAHD film was successfully deposited on some material surfaces such as SS, Ti, TiNi, TiO2, glass and polytetrafluoroethylene (PTFE). The GAHD chemical structures, reaction mechanism and the film forming process were explored through Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), time of flight secondary ion mass spectrometry (TOF-SIMS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and so on. The effect of base concentration, Tris, deposition layers, deposition time and the reaction temperature on the density of carboxyl and amine groups was studied by carrying out colorimetry, FTIR, XPS and AFM tests. Fibronectin (FN), Heparin (HEP) and Laminin (LN) were immobilized on surface of GAHD film by reacting with amine, carboxyl and quinone groups respectively. Immunofluorescence staining and enzyme-linked immunosorbent assay (ELISA) were carried out to qualitatively and quantitatively prove the three kinds of biomolecules were successfully linked on the GAHD film surface.Furthermore, after vascular stents are implanted, there are still some problem such as in-stent restenosis, incomplete coverage of endodermis, late thrombosis, and chronic inflammation. Indeed, atherosclerosis is an immune inflammatory disease. The general treatment strategies, such as inhibiting of smooth muscle cells (VSMC) proliferation, promoting endothelialization and anticoagulant, could not fully improve the inflammation environment at atherosclerotic lesions. The newborn endothelial cells (VEC) and VSMC will be dysfunction, apoptosis and proliferation again with time passing. Therefore, it is necessary to develop a new kind of surface modification technique which directly inhibits inflammatory responses of VEC, VSMC and inflammatory cells. In this thesis, different density of GA and HD surfaces were construct by changing the ratio of GA and HD, carrying out vacuum heat treatment and chemical reduction The proliferation, migration, function, phenotype and inflammatory response of VEC, VSMC and inflammatory cells were explored by cell counting kit-8 (CCK-8), rhodamine staining, cell count, cell morphology analysis, ELISA, and enzyme-linked immunoassay kit (KIT). It can be found that, after the GAHD film treated, the GAHD film could protect VEC survival and promote migration, inhibit proliferation and migration of VSMC, suppressed nitric oxide (NO) and prostacyclin (PGI2) secreting from VEC, induce VSMC phenotype to transform contractile phenotype, and inhibit inflammatory cytokines from macrophages and VSMC to be secreted and activated but had no significant effect on inflammatory cytokines secreted from VEC. These effects may be related to regulation of cyclin A (cyclin A) and cyclin E (cyclin E) expression by GA, as well as different responses to VEC and VSMC, producing or suppressing reactive oxygen species (ROS), stimulated by GA.316L stainless steel substrate as cardiovascular stents, its non-biodegradable nature may result permanent physical stimulation and chronic inflammation for organization, and the release of toxic metal ions. Magnesium metal as a biodegradable metallic material may solve above problems, but its rapid degradation rate restricted its application. The current anti-corrosion surface modification method can slow down the corrosion rate of magnesium metal, but most methods also require expensive equipment and complicated operation process, and could not continue to introduce biofunction on this basis. Therefore, it is necessary to develop a new kind of corrosion resistant surface modification technique which is inexpensive, simple operation, and can immobilize biomolecules. In our thesis, GAHD film was successfully deposited on the magnesium alloy (MZM) surface. By electrochemical detection (polarization curves and EIS Nyquist spectrum) and immersion test (Mg2+ concentration, OH- concentration and weight loss), it was proved that compared to MZM, MZM-GAHD film significantly improved the corrosion resistance. Corrosion-resistant mechanism of the GAHD film was explored by analyzing comprehensively results of FTIR, XPS and elemental depth analysis, and anti-corrosion tests. In addition, the HEP molecules were successfully immobilized on MZM-GAHD surface by carbodiimide (EDC) method. The evaluation of platelet adhesion and clotting time test showed that MZM-HEP-GAHD had higher anticoagulation than MZM-GAHD. Finally, in vivo experiment indicated that mass loss had no significant difference between MZM-1:1, MZM-HEP-1:1 and MZM, however the trend still showed MZM-1:1, MZM-HEP-1:1 possessed corrosion resistance property. Histological sections micrograph showed that the histocompatibility of MZM-1:1 and MZM-HEP-1:1 was better than that of MZM. |
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