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Fabrication and Characterization of Nanocomposite Bone Scaffold with Gradient Structure Based on Thermoplastic Starch

Mirab, Fereshteh | 2015

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48193 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Bagheri, Reza
  7. Abstract:
  8. Tissue regeneration by bio-compatible/degradable scaffolds is one of the widely used approaches in the field of tissue engineering. In this study, a thermoplastic starch based nanocomposite scaffold with gradient structure was fabricated by unidirectional freeze drying method. To increase the stability of the scaffold in the aqueous media, PVA was added to starch solution. Then, the PVA and starch molecules were cross-linked by adding citric acid to the mixture. On the one hand, to improve the mechanical properties of the scaffold, and control its bio-degradability on the other, cellulose nano-fibers were employed. Also, the bioactivity of the scaffold was induced by using hydroxyapatite (HA) nano-particles. The structure and properties of the scaffold were characterized using physical, mechanical, and biological tests and also microscopic observations. Using FTIR spectroscopy, it was shown that the PVA and starch molecules have been chemically cross-linked in the scaffold’s matrix. Microscopic observations revealed the presence of unidirectional gradient porous structure with the pore size of 80-300 micrometers at the scaffold. It was illustrated that the cellulose nano-fibers and HA nano-particles have desirable dispersion and distribution in the matrix, and their average size were respectively measured as 48 nm and 32 nm. Appropriate adhesion and dispersion of the rigid nano-reinforcements within the matrix increased the elastic modulus and Yield strength of the scaffold by 109% and 39%, respectively, with respect to the neat matrix. Cellulose nano-fibres decreased the degradation rate of the scaffold, but on the other hand, the HA nanoparticles accelerate the degradation rate. Furthermore, the well-dispersed HA nanoparticles with high surface area led to the high bioactivity of the scaffold. The results of MTT assay proved the nontoxicity of the scaffold, and showed the minimum viability of 94% in the all samples. At last, the suitable adhesion of living cells to the scaffold was confirmed by the cell adhesion test
  9. Keywords:
  10. Thermoplastic Starch ; Cellulose Nanofiber ; Bone Scaffold ; Thermoplastic Starch ; Gradient Scaffold ; Hydroxyapatite Naoparticles ; Unidirectional Freeze Drying

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