الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Composite natural polymers/bioceramics scaffolds are considered promising in hard tissue engineering, as they combine the advantages of different materials and benefits from the flexibility and easy shaping of polymers with the higher strength, stiffness and bioactivity of the bioactive ceramics, achieving the best mechanical and biological performance. Thus, the current study aimed at preparing and characterizing undoped and Ag-doped BG nanoparticles, fabricated using two different methods; sol-gel-derived BG nanoparticles (BGsg and Ag-BGsg) and monodispersed BG nanoparticles (BGm and Ag-BGm) fabricated using modified Stöber method. This was followed by the fabrication of a three-dimensional (3D) nanocomposite porous zein scaffolds incorporating the prepared undoped and Ag-doped BG nanoparticles to investigate their chemical, biological, mechanical and physical properties in comparison to the pure zein scaffolds.
Salt-leaching process using sodium chloride (NaCl) as porogen was used to fabricate porous zein and nanocomposite zein:BG scaffolds containing the four different BG powders, BGsg, Ag-BGsg, BGm and Ag-BGm. SEM was used to observe the morphology and microstructure of the five scaffolds groups, pure zein, zein:BGsg, zein:Ag-BGsg, zein:BGm and zein:Ag-BGm. SEM micrographs showed that all the five scaffolds groups are porous with a wide range of pore diameter. FTIR spectrum of pure zein scaffold showed the three characteristic amide peaks for zein protein, which corresponds to amide I, amide II and amide III. Zein:BG scaffolds showed additional peaks characteristic of SiO2 based glasses.
The in vitro HA forming ability of the prepared scaffolds was investigated in SBF, the incubated scaffolds were examined using SEM and FTIR spectra analysis. Pure zein scaffolds incubated in SBF showed lack of bioactivity, as evident by lack of HA mineral formation on the surface of zein, after 7 and 14 days. Also, zein scaffolds containing monodispersed BG (zein:BGm and zein:Ag-BGm) incubated for 7 and 14 days in SBF showed no HA crystals formation. On the other hand, zein scaffolds containing sol-gel-derived BGs (zein:BGsg and zein:Ag-BGsg scaffolds) showed the formation of rounded shaped HA crystals only on the
surface of BG, with distinct interface between the formed HA crystals and adjacent zein surface.
Disc diffusion assay showed that only zein scaffolds containing Ag-BGsg showed positive antibacterial activity against E. coli and S. aureus, while all other scaffold groups, including the zein:Ag-BGm group, showed no antibacterial effect .
Human osteoblast-like MG-63 cells (human osteosarcoma cell line) were used to evaluate the in vitro biocompatibility of the prepared five scaffold groups. Scaffolds were seeded with the cells, and at the predetermined time points (1, 3, 7 and 14 days), cell viability was measured using WST-8 cell counting kit (CCK-8) (Cell Counting Kit – 8) (n=3). Results showed the ability of MG-63 cells to survive and proliferate on the pure zein, zein:BGsg and zein:Ag-BGsg scaffolds. On the other hand, data showed decreased cell count observed with the zein:BGm scaffolds, while cell count showed almost no change on the zein:Ag-BGm scaffolds.
Hence, the monodispersed BG-containing scaffolds, zein:BGm and zein:Ag-BGm groups, were excluded from further characterization tests based on the results of the antibacterial activity and cell viability and proliferation tests.
ALP enzyme activity assays was used as marker for MG-63 cells differentiation and activity on the pure zein, zein:BGsg and zein:Ag-BGsg scaffolds (n=3). Results of the ALP activity assay showed that ALP activity followed a different trend to the proliferation behavior observed with WST-8, where zein:BGsg showed no statistically significant difference compared to other groups at most of the time points. The zein:BGsg group had a more positive Alizarin Red S staining as an indicator of calcium phosphate mineral nodule formation, when compared with pure zein and zein:Ag-BGsg scaffolds.
The compressive strength of the three scaffold groups was determined using uniaxial compression strength testing (n=5). Results showed no statistically significant difference in the mean compressive strength among the different groups.
The interconnected porosity (Øc) of the three scaffolds groups (n=6) was measured using helium pycnometer. All the three scaffold groups exhibited high pore interconnectivity (> 65%). Zein:BGsg exhibited the significantly highest mean porosity, while the total porosity of pure zein was statistically significantly lower than the other two groups.