Hybrid chitosan-alginate scaffolds for bone and cartilage tissue engineering

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Hybrid chitosan-alginate scaffolds for bone and cartilage tissue engineering

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Title: Hybrid chitosan-alginate scaffolds for bone and cartilage tissue engineering
Author: Li, Zhensheng, 1972-
Abstract: The regeneration of new bone or cartilage to restore the function of traumatized, damaged, or lost bone or cartilage is a major clinical and socioeconomic burden. In recent years, a new cutting-edge procedure, bone- and cartilage-tissue engineering, has emerged as a new strategy for healing musculoskeletal conditions. In this strategy, progenitors or mature cells are combined with biocompatible scaffolds to initiate partial or full bone and/or cartilage regeneration.Scaffolding materials in tissue engineering should be bioactive and biodegradable. The synthetic polymers, such as PLA and PGA, are biodegradable, but not bioactive. Furthermore, their bulky degradation style and induction of foreign body reaction limit their clinical applications. Chitosan and alginate, two natural polymers, have proven to be biodegradable and bioactive for bone and cartilage regeneration. In this study, high-concentration (4.8% w/v) chitosan-alginate hybrid scaffolds were successfully synthesized through a thermally-induced phase separation technique. The produced hybrid scaffold was thoroughly characterized for mechanical and biological properties and compared to pure chitosan scaffolds of the same concentration and similar porosity. The main pore sizes of the porous hybrid scaffolds was found to be 50--300 mum, which can be controlled through freezing and coalescence processes. The hybrid scaffolds demonstrated significantly-improved mechanical strength, water permeability and stability compared to pure chitosan scaffolds at increased porosity (92-95% vs. 87-89%).The in vitro study showed that the hybrid scaffold induced better cell attachment and proliferation rate, and maintained the functionality of the cells better than chitosan scaffolds. The hybrid scaffolds were also shown to promote the biomineralization of MG-63 osteoblast and the production of collagen type II, and maintain the characteristic cell morphology of chondrocytes. In vivo study showed that the hybrid scaffolds were biocompatible and degradable, and, promoted rapid vascularization, deposited connective tissue, and calcified matrix within the whole scaffold structure. The results support the potential applications of chitosan-alginate scaffolds as an alternative to other natural polymer-based scaffolds in tissue engineering. This study provides insights to the principles of interactions between biodegradable composite materials and biological systems, and the information for fabrication of scaffolds of different mechanical strengths for desired clinical applications.Key words: tissue engineering, chitosan, alginate, lyophilization (freeze drying), bone, cartilage
Description: Thesis (Ph. D.)--University of Washington, 2007.
URI: http://hdl.handle.net/1773/10609

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