Scaffolds for Tissue Engineering
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Scaffolds for Tissue Engineering
Jeffrey M. Karp, Paul D. Dalton, and Molly S. Shoichet Abstract Devices for tissue engineering comprise scaffolds with the appropriate chemistry and architecture to promote cell infiltration and colonization. The scaffold is designed with biology in mind, and thus the architecture and chemistry differ according to tissue type. In this review, we focus on scaffolds for two tissue types—bone and nervous tissue— and describe different approaches used to create them. The appropriate scaffold for a hard tissue such as bone has a high degree of interconnected macroporosity and allows the rapid invasion of cells while maintaining a rigid structure. Several approaches are described for constructing tissue-engineering scaffolds for bone. The appropriate scaffold for soft tissues like nerve fibers (e.g., axons, which conduct nerve impulses) also has a high degree of interconnected pores; however, the pores may require orientation and may be smaller. Homogeneous, high-water-content hydrogels with mechanical properties that match the soft nerve tissue are commonly used as a scaffold, and the methods used to make these are reviewed. Keywords: cellular solids, open-cell foam, polymers, scaffolds, tissue engineering.
Introduction Tissue engineering has evolved out of the need to repair organs and tissues damaged by disease or injury. While the “gold standard” for regeneration and healing is the autograft, this approach is inherently limited by the amount of available donor tissue and necessitates a second injury site, resulting in additional trauma to the patient and associated risks such as pain, infection, and donor-site morbidity (dead tissue at the donor site). The concept of tissue engineering embodies the creation of a scaffold structure that has the appropriate physical, chemical, and mechanical properties to enable cell penetration and tissue formation in three dimensions. The appropriate scaffold for tissue engineering will be one that is created with biology in mind. The goal is for the new tissue grown in the scaffold to integrate with the host tissue. Ideally, the scaffold provides a temporary pathway for regeneration and will degrade either during or after healing, thereby obviating the need to remove the material later and eliminating possible side effects associated with leaving materials in the body. Of course, attention must be paid to ensure that degradation products are non-cytotoxic.
MRS BULLETIN/APRIL 2003
While there are numerous methods for creating scaffolds, most of these do not take biology into consideration and thus have limited efficacy. Perhaps one of the greatest challenges faced in tissueengineered devices, regardless of tissue type, is promoting healing in three dimensions. Allowing blood-vessel formation (angiogenesis) throughout the scaffold is also critical to the success of the scaffold. In this article, we review the most promising scaffold approaches for the regeneration of two tissue types: bone and neural tissue. We chose to focus on these tissues for t
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