3 - Hydrogels in cell encapsulation and tissue engineering

Abstract

This chapter explains that hydrogel is a network of hydrophilic polymers that absorbs water or biological fluid but does not dissolve. Hydrogels can be created from a number of water-soluble materials and commonly include synthetic polymers, proteins, and natural molecules. The three-dimensional (3D) structure of hydrogels is a result of polymer cross-linking that forms an insoluble structure within the fluid environment. The high water content and elasticity create a resemblance to biological tissue, creating extensive biomedical applications. A few scientists have even hypothesized that a primitive hydrogel may have provided the environment responsible for assembly of the first cell (Trevors and Pollack, 2005). Biomimetic hydrogels have great potential for in vivo applications of tissue engineering. Growth factors and other bioactive molecules that are regularly added to media to enhance in vitro chondrogenic differentiation are added to hydrogel for local delivery with in vivo implants. Greater control over the release of growth factors when needed by encapsulated cells should significantly improve cartilage tissue production. There is a need for further studies of tissue-engineered cartilage in large-animal models. The current focus on in vitro and small-animal in vivo studies is appropriate for answering fundamental questions regarding the properties of engineered tissues, but translation to large-animal models will be critical for clinical translation. As certain tissue-engineering techniques come closer to clinical application, there will be a need for in vivo testing that more closely approximates the conditions and stresses that will be encountered by engineered tissues implanted in humans.