| Nanobiotechnology, as the cross-discipline of nanotechnology and life science, is a novel technology and approach to investigate life science at nanoscale level. In this paper, a dual membrane diffusion system (DMDS) was used to investigate the mineralization behaviour of collagen. Simulating the biomineralization, this paper applied a new route for preparing hydroxyapatite-based composite by enzymatic decomposition of urea. As a drug delivery system to cure osteomyelitis, chitosan/Hydroxyapatite-gentamicin was prepared for the treatment of osteomyelitis, and the antibacterial mechanism of antibiotic was detected with AFM. The effect of gentamicin on the composite material was investigated as well. From the results, we obtained a lot of valuable information shown as the following:1. A model dual membrane diffusion system was used to detect the mineralization behaviour of collagen. The process of mineralization was observed by atomic force microscope (AFM). The micromechanical properties and microstructure changes of collagen fibers in the process of mineralization suggested that the mineralization was a step-by-step assembling process. In the initial stage, when the supersaturated condition was created in the DMDS, monomeric collagen converted into larger fibrils. These mineralized fibrils self-assembled into loose-arrayed fibers, which has no typical cross-striation patterns. In the second stage, loose-arrayed fibers arranged closely with each other and further assembled into slenderer but tighter ones. It represented the typical cross-striation pattern, which was similar with nature collagen. In the final stage, the fibers became thicker and stiffer due to the further growth of HA crystal within collagen fibrils. The phenomenon that calcium phosphate solid-phase appeared in the initial-and medium-stage and disappeared in final-stage supported the hypothesis of "polymer-induced liquid-precursor mineralization process". Moreover, the difference in height between the peak and bottom in typical cross-striation patterns on collagen fibers was measured by AFM. The differenceinheight of nature collagen fiber was about 5 nm, while it was 2.4-4.3 nm on minerized collagen fiber. The structural investigation by AFM supplied new evidence on the hypothesis that HA preferentially grows into the hole zones and interstices of the collagen fiber as reported by Landis. 2. Simulating the biomineralization, we applied a new route for preparing hydroxyapatite-based composite by enzymatic decomposition of urea. The composite materials were characterized by XRD, laser diffraction particle size analyzer, SEM and TEM. The results of FTIR and TEM indicated that chemical and crystallographic properties of the complex were similar to the properties of nature bone. Laser diffraction particle size measurement and SEM showed that the samples were of smaller particle size and narrower particle size distribution particle sizes than those prepared by traditional co-precipitation method. The degradation of the composite materials was investigated via simulation in vitro. The results showed that these materials had excellent degradability.3. Chitosan/Hydroxyapatite-Gentamicin (CS/HA-G) was prepared, and this drug delivery system (DDS) was tested in vitro release ratio and antibacterial activity against bacteria. We used AFM to probe the surface ultrastructure of bacteria before and after CS/HA-G treatment. The results showed that CS/HA-G had considerable delayed release effectivity. It maintained effective release time of gentamicin up to 30 d, and its inactivation against bacteria was remarkable. AFM ultrastructure images showed that the height and the Ra (average roughness) of cells were all decreased. The cell content leaked via damaged cellular membrane. The CS/HA composite is a promising local biodegradable delivery system for gentamicin in treating osteomyelitis.4. In order to investigate the effects of gentamicin on properties of hydroxyapatite/chitosan, CS/HA-G and CS/HA composites were prepared by co-precipitation method. The products were characterized by FTIR, XRD and SEM. This paper reported on comparison of chemical property and antibacterial activity between HA/CS-G and HA/CS. Comprising with HA/CS, HA/CS-G exhibitied much higher compressive strength and better antimicrobial activity. Moreover, molding technique of uniaxial pressure following cold isostatic pressure gave materials much higher compressive strength than technique of cold isostatic pressure. HA/CS-G can be used as an ideal gentamicin carrier and has great potential in osteomyelitis therapy.5. The microstructural and micromechanical properties of chitosan were very important for its bioapplications as scaffolds for tissue engineering or carrier for drug delivery. Different drying conditions greatly affected the microstructural and micromechanical properties of chitosan. Chitosan films were prepared by wet casting followed by vacuum drying (VD) and...
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