tailieunhanh - Chapter 069. Tissue Engineering (Part 2)

Scaffolds A scaffold provides a three-dimensional framework to support the tissue or organ-specific cells. The scaffold not only provides mechanical support, but it must also supply critical nutrients and transport metabolites to and from the developing tissue. Important scaffold properties vary depending on the tissue but typically include specific biomechanical properties, porosity, biocompatibility, and appropriate surface characteristics for cell adhesion and differentiation. Scaffolds can be natural materials or synthetic polymers and are typically biodegradable. Natural materials such as collagen and alginates are biocompatible. However, it is difficult to control their mechanical properties, and they may generate an immune reaction. . | Chapter 069. Tissue Engineering Part 2 Scaffolds A scaffold provides a three-dimensional framework to support the tissue or organ-specific cells. The scaffold not only provides mechanical support but it must also supply critical nutrients and transport metabolites to and from the developing tissue. Important scaffold properties vary depending on the tissue but typically include specific biomechanical properties porosity biocompatibility and appropriate surface characteristics for cell adhesion and differentiation. Scaffolds can be natural materials or synthetic polymers and are typically biodegradable. Natural materials such as collagen and alginates are biocompatible. However it is difficult to control their mechanical properties and they may generate an immune reaction. Synthetic polymers such as polyglycolic acid and polyethylene on the other hand can be tailored to provide more acceptable mechanical properties but are associated with a strong inflammatory response. Nonbiodegradable synthetic polymers such as polytetrafluoroethylene and polyethylene provide well-defined mechanical and structural properties. However their long-term presence in the body can lead to a chronic inflammatory response which results in poor tissue quality. Polylactic acid and polyglycolic acid are examples of biodegradable polymers. Although the degradation of these materials can be partially controlled nonuniform degradation and varying degradation rates in different anatomic locations represent challenges. The surface properties of the materials used for the scaffold are important for adhesion migration and cell differentiation. Ongoing research is focused on tethering growth factors or peptide sequences to the surface of the scaffold to improve adhesion and migration. Bioreactors Initially cells used in tissue engineering were cultured in static conditions. Improvements in bioreactor technology more closely approximate physiologic parameters for tissue growth. By modulating rates of