| Gelatin, a denatured collagen treated by acid or alkali, is a condensation polymer of a variety of amino acids. Because of the multiple excellent dipersion functions, gelatin has been ued in the traditional application of photosensitive materials for more than one handred years. At present, study on gelatin is mainly focused on soft and hard tissue engineering materials due to gelatin possessing rich sources, good biocompatibility and high reactive activities. Furthermore, gelatin can be used as an ideal material for nanotechnology because of its excellent emulsifying properties, high reactive activities of side chains and good biocompatibility. In this dissertation, we use gelatin as raw materials to synthesize porous copolymer film materials, tissue engineering material with antibacterial activities, noble-metal nanoparticles and gelatin-ZnO composites. The dissertation is mainly focused on:1. Synthesis of ordered porous gelatin-g-PMMA filmDue to gelatin possessing suspended double bonds, alkene monomers such as methyl methacrylate (MMA) can be grafted onto gelatin polypeptide chains. We optimized PMMA, a side product in the graft copolymerization of gelatin and MMA via traditional free radical initiation, act as a template to create ordered nanoporous gelatin-g-PMMA film materials. The pore size of gelatin-g-PMMA film can be controlled by adjusting copolymerization technics and the physical-chemical interaction of gelatin and PMMA. The monolayer or multilayer nanoporous film can be prepared by adjusting the solid content of gelating-PMMA latex. This approach has been successfully extended to chitosan-g-PMMA and gelatin-g-PS systems. This study provides not a new approach to synthesize ordered and porous copolymer films, but also explores a new research area of traditional free radical copolymerization to synthesize novel functional materials.2. Synthesis of gelatin-g-PMMA/silver nanoparticle hybrid porous films and the evaluation of their antibacterial activityGrafting PMMA chains onto gelatin is not only to improve the gelatin film adhesion and wetting behavior to avoid dissolution at body temperature (37?), but also to synthesize Ag nanoparticle growth regulated by amphiphilic gelatin-g-PMMA to prepare gelatin-based tissue engineering materials with antibacterial activities. The antibacterial activities of the films to Escherichia coli and Staphylococcus aureus were evaluated. The experiment result testified that the ideal antibacterial gelatin-g-PMMA/Ag tissue engineering material has been synthesized. When we selected the mass ratio (MMA/gelatin) of 1 to prepare the gelatin-g-PMMA/Ag film, the grafting percentage of gelatin is 42%, which make gelatin-g-PMMA film posses relatively higher water solubility. When the Ag nanoparticle concentration in the gelatin-g-PMMA/Ag film is 26.5 mg/g (mAg/mgelatin), the pore size of the gelatin-g-PMMA/Ag film was about 3 nm. The size of Ag nanoparticles embedded in the film was about 6 nm. When the concentration of gelatin-g-PMMA/Ag in bacteria liquid is 50?g/mL, the gelatin-g-PMMA film possesses clear and lasting antibacterial activity. The inhibition efficiency against E. coli and S. aureus was more than 98%.3. Biomimetic synthesis of gelatin-assisted noble-metal nanoparticles and their interaction studyThe generation of gold, silver, and Ag-Au bimetallic nanoparticles was carried out by using gelatin as reducing and stabilizing agents. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV-visible, fluorescence spectroscopy, and 1HNMR. The shape control and the aggregation behavior induced by salt (NaCl) and pH of nanoparticles were discussed. The results were obtained from experiments as follows:(a) The components of gelatin, glutamic acid and hydrophobic praline, acted as reducing agent determined by 1HNMR to biomimetically synthesize noble metal nanoparticles at 80?. (b) The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. (c) There is strong interaction between nanoparticles and gelatin to keep gelatin-Au?gelatin-Ag and gelatin-Au-Ag colloids very stable. In which, the interaction between amino groups of gelatin and nanoparticles is strongest. Due to many amino acid arrays possessing strong binding affinity to Au nanoparticles, gelatin-Au colloid is very stable against aggregation induced by salt (NaCl) and pH. (d) It has been testified that a ground state complex is formed between gelatin and AuNPs. Gelatin polypeptide chain is a random polymer chains bond by nanopartiles in solution above the sol-gel temperature. Nanoparticles is not only stabilized by gelatin polypeptides chains but also joined in the self-assembling activities of gelatin polypeptides to form three-dimensional a-helix folding chains upon cooling to room temperature.4. ZnO-gelatin composites were prepared by continous flow injection methodsCuboid, hexagonal twin crystal and plate-like ZnO mesocrystals were successfully synthesized by using gelatin as directing agent via continuous flow injection methods. The effect of the flow rate and temperature on the crystal growth was discussed. When the reaction temperature is stable, the size of nanoparticle is becoming smaller and mono-dispersed, while the shape of nanoparticle is not changeable. When the flow state of liquids is stable, the greatly change of reaction temperature affect the shape of nanoparticles. The negative carboxylate charge groups in gelatin strongly interact with the (0001) polar plane of ZnO. A large number of carboxylic groups in gelatin are able to coordinate with Zn2+ to decrease the surface energy of (0001) and suppress its growth along c-axis. The ZnO nanocrystals precipitate on the surface of the gelatin macromolecules and are self-assemble into ZnO-gelatin superarchitectures. |
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