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Studying the Influence of Laponite Silicate Nanoparticles on the Mechanical and Structural Properties of Poly (Ethylene Glycol) Hydrogels, Synthesized under Mild Condition

Nojoomi, Amirali | 2013

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 44924 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Simchi, Abdolreza; Maddah Hosseini, Hamid Reza
  7. Abstract:
  8. Hemophilia is a group of hereditary genetic disorders that impair the body's ability to control blood clotting due to the lack of coagulation factors. Frequent joint and soft tissue bleeding is one the most common problems amongst these patients which can become progressively destructive for cartilage tissue in case of the late treatment. In this work, injectable PEG-based hydrogel nanocomposites with mechanical and structural properties close to cartilage tissue were fabricated. First, primary copolymers with PEG blocks of 600 g.mol-1 and 900 g.mol-1 without and with 2.5 wt.% Laponite nanoclay were synthesized by two-step thermal poly (amic acid) process. After polymer purification, hydrogel samples were gel-casted in the presence of butane diamine (BDA) as nucleophilic reagent under ambient condition. Successful copolymer synthesis and hydrogel formation were confirmed by C-NMR and FTIR analysis. The rheological behavior of the hydrogel as an indicator of its injecting ability was investigated by Cone-Plate measuring geometry. Analysis of the rheological data was performed by rheological models of cross, modified Carreau and Carreau-Yasuda. Viscoelastic properties were studied by oscillatory shear stress assay. Results showed improved elastic modulus of the studied PEG based hydrogels (5 to 10 fold of magnitude) compared to the conventional PEG hydrogels. The measured modulus of elasticity was about 90% of natural articular cartilage. Scanning electron microscopy studies showed that the hydrogels contain interconnected pores with sizes in the range of 100-250 μm after incubation in simulated body fluid at 37°C for 72 hours. MTT assay was performed using L929 mouse fibroblast cell lines to investigate the cytotoxicity of the fabricated scaffolds. High local concentration of BDA coupled with relatively low cell seeding (<105 cells.cm-2) made MTT results lower than what we expected. However, better results would be attained at higher seeding densities
  9. Keywords:
  10. Hydrogel ; Imide Ring Opening ; Polyethylen Glycol (PEG) ; Cartilage Scaffold ; Leponite

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