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Design and Fabrication of Conductive Polymeric Nanocomposite Scaffolds for Nerve Tissue Engineering

Baniasadi, Hossein | 2015

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 47169 (06)
  4. University: Sharif University of Technology
  5. Department: Chemical and Petroleum Engineering
  6. Advisor(s): Ramezani Saadat, Ahmad
  7. Abstract:
  8. In the current study, design, fabrication, and characterization of a novel conductive nanocomposite scaffold for nerve tissue engineering applications is reported. For this purpose, the highly conductive polyaniline/graphene nanocomposite (PAG) was synthesized via emulsion polymerization, used for fabrication of conductive chitosan/gelatin/PAG scaffolds, and the effect of PAG amount on the various properties of scaffolds were investigated. The synthesized graphene, polyaniline, and PAG were characterized and the obtained results revealed that partially exfoliated graphene nanosheets and highly conductive PAG with a conductivity of about 12 S.cm-1 and 7 S.cm-1, respectively were obtained. The prepared chitosan/gelatin/PAG scaffolds were also characterized and the results demonstrated that by adding PAG into scaffolds the conductivity and tensile modulus were increased while porosity and swelling ratio (hydrophilicity) decreased. The electrical conductivity of chitosan/gelatin scaffold increased from about 10-7 S.cm-1 to about 0.002 S.cm-1 just by adding 2.5 wt.% PAG which made it proper candidate for neural tissue engineering with the regard of electrical conductivity. Adding 2.5 wt.% PAG into chitosan/gelatin scaffold was reduced the porosity and the swelling capacity 10% and 30%, respectively. Nevertheless, the porosity and hydrophilicity of this scaffold were still in the proper range for tissue engineering applications. The in vitro biodegradation of scaffolds were also investigated and it was found that conductive scaffolds were degraded much slower than pure chitosan/gelatin one probably due to more hydrophobicity properties of conductive scaffolds made difficult for water to penetrate into polymeric networks. The results of MTT assay of cultured Schwann cells 1, 3, 7, 10, and 14 days after culturing showed that although all scaffolds were non-toxic but, the cell proliferation rate decreased with increasing PAG amount. Furthermore, there was not observed any significant differences between the proliferation rate of pure scaffold and conductive one with 2.5 wt.% PAG. The biocompatibility of this scaffold was also confirmed by good attachment and spreading of Schwann cells which was observed on SEM images. In addition, the effect of electrical stimulation on the proliferation and morphology of cultured Schwann cells on the scaffold with 2.5 wt.% were also investigated and the obtained results showed that pulsed electrical stimulation with voltage of 100 mV/mm and time step of 1 sec were more effective on proliferation of cells compare to direct electrical stimulation as well as pulsed one with larger time steps. Furthermore, the SEM images showed that the electrical stimulated cells illustrated needle shape with significant extension of neuritis compare to non-stimulated ones which more confirmed the positive effects of using electrical stimulation. Finally this work supports the potential use of gelatin/chitosan/polyaniline/graphene compounding as a proper biomaterial for using in nerve tissue engineering applications
  9. Keywords:
  10. Nerve Tissue Engineering ; Conductive Polymer ; Electrical Stimulation ; Schwann Cell ; Scaffold ; Biocompatibility

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