الفهرس 
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Abstract
The present thesis includes preparation, characterization and studying the structural changes of two prepared systems. The first system concern ’’structural properties of pure materials (hydroxyapatite (HAp), chitosan (Cs), and polyacrylic acid (PAAc)’’ in which Hap was obtained in powder form by wet-chemical precipitation method but Cs and PAAc films were prepared by casting technique. Nano-particles of hydroxyapatite (HAp) were prepared via an in-situ biomimetic process with polyacrylic acid (PAAc) and chitosan (Cs) as host polymeric materials. HAp formation was initiated through the interaction of Ca2+ ions with the negative side groups of the polymer surface. X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR) thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) were used to test the physical and chemical characteristics of pure and biocomposite materials. The formation of hydroxyapatite is confirmed by energy dispersive X-ray (EDX) spectroscopic analysis. Chemical binding between inorganic HAp and the inorganic matrix was investigated and discussed. They confirm that the HAp was obtained in nano scale without any impurities and Cs and PAAc were obtained in amorphous form with identical characteristic peaks. The results showed that the biocomposites were formed with good homogeneity and thermal stability. Nano-particles of HAp were uniformly distributed in the polymeric matrix. The resulting new materials are hoped to be applicable in the biomedical fields. The second system concern nano-particles hydroxyapatite (HAp) was prepared via an in-situ biomimetic process with polyacrylic acid (PAAc) and chitosan (Cs) as a host polymeric material with inorganic/organic ratio 60/40 wt%. Silver nitrate with different concentrations was added to improve the physical properties and bioactivity of the biocomposite. Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD), were used to test the physical and chemical characteristics of biocomposites. Kinetic parameters were determined from the weight loss data using non isothermal thermogravimetric analysis (TGA). The main decomposition temperatures and the main degradation step were describes and discussed. The SBF incubation test confirmed that the fast formation of apatite-like materials suggests in vitro bioactive behavior of the biocomposite, possibly due to the addition of metallic Ag nanoparticles. This study demonstrated that Ag nanoparticles in HAp/PAAc-Cs-Ag biocomposite activates bioactivity and supports growth of apatite-like materials. Also, the prepared composite are evaluated for their antimicrobial activity against Gram-positive and Gram-negative bacteria and fungal strains. The specific antimicrobial activity revealed by the qualitative assay is demonstrating that our composites are interacting differently with the microbial targets, probably due to the differences in the microbial wall structures. Thus the resulting new materials are hoped to be applicable in the biomedical fields.