الفهرس 
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Abstract
Although bone tissue has a natural ability to regenerate itself, it has difficulty regenerating critical defects, which requires additional support to enhance the regeneration process. To solve this problem, 3D porous bone scaffolds have become a cornerstone of tissue engineering and regenerative medicine applications due to their ability to avoid drawbacks of conventional bone grafts such as the potential for infection, viral disease transmission, and immune rejection. Manufactured porous bone scaffolds must be able to strengthen the connection between bone cells, provide mechanical stability, and must degrade over time and be eliminated from the body without side effects. Also, their ability to overcome the clinical challenges: resistance to bacterial activity at surgical sites, and the ability to prevent recurrence of cancer after surgical removal. In this respect, hydroxyapatite (HAp) and gelatin, whose properties are similar to those of bone-forming materials, are among the best biomaterials candidates for the fabrication of bone scaffolds . In this thesis, porous scaffolds based on biphasic calcium phosphate (BCP: a mixture of HAp and β-tricalcium phosphate (TCP)) and polymer (gelatin and polyvinyl alcohol (PVA)) composite hydrogel was designed by using a lyophilization technique. BCP nanoparticles were prepared in situ in gelatin and PVA at polymer/BCP ratios equal to 0.2, 0.4 and 0.6. Conventional techniques: XRD, FTIR, TGA-DTA, and SEM were used to examine the structure of the fabricated scaffolds. The mechanical properties (stress-strain behavior) and in vitro swelling and degradation studies of the scaffolds were also studied. The results showed the formation of well-dispersed BCP particles in scaffolds with different HAp/TCP ratios. Scaffolds with lower content of BCP exhibited higher porosity and somewhat higher mechanical properties, lower diffusion of ceramic particles into fine pores and reduced pore size shrinkage compared to those with higher content of BCP nanoparticles. The scaffolds had good mechanical compressive strength in the range of 40-70 kPa, porosity of 10-90% and pore size of 10-310 μm. They exhibited high permeability, high swelling capacity of up to 800%, long-term swelling and degradation behavior of up to 42 days. On the other hand, synergistic multifunctional porous scaffolds have been developed to treat damaged bone tissue at injured sites prone to bacterial infection and carcinogenesis. BCP/gelatin-PVA scaffolds loaded with antibacterial silver nanoparticles (Ag NPs: 0.25 wt% and 2 wt%) and loaded with the anticancer methotrexate (1.25 wt%). BCP nanoparticles were prepared in situ in a PVA matrix using the coprecipitation method and scaffolds were fabricated using the freezedried method. The results showed the formation of the two constituent phases of BCP (HAp and TCP). The scaffolds showed good mechanical compressive strength in the range of 28- 173 kPa, elevated total porosities close to 80%, and pores with dimensions ranging from a few microns to 300 μm. They have a swelling capacity of up to 400% with a long-term degradation behavior for up to 28 days and a rapid release of methotrexate within the first day. The silver-free scaffolds containing HAp nanoparticles and those containing Ag nanoparticles yielded antibacterial activity against pathogenic bacteria. Methotrexate and Ag (0.25 wt%), individually and in combination, had no cytotoxic effect on Vero cells and human osteosarcoma MG-36 cells after one day compared to cytotoxic Ag (2.0 wt%).