The term tissue engineering is often synonymous with regenerative medicine. It is essentially the use of a combination of engineered material constructs, suitable biochemical factors and/or cells to improve or replace the function of a failing organ. Other applications of tissue engineering are the testing of drug efficacy and toxicity, as well as the basic studies of tissue development (Berthiaume, Maguire, & Yarmush, 2011).
Most tissue engineering methods utilize living cells; therefore the supply of reliable cells is essential. Cells are derived from two sources: 1) donor tissue and 2) stem cells. Stem cells have a high proliferative capacity and are pluripotent, making them suitable for deriving large cell quantities.
Another important issue to consider in tissue engineering is the cellular environment. The ideal environment allows cells to function as they normally do in native tissue. This can be mimicked through control of materials, mechanical settings, and the chemical background, hence the use of cell scaffolds (Berthiaume et al., 2011).
Scaffolding usually provides one of the following (Berthiaume et al., 2011):
a. Cell attachment and possibly migration
b. Retention and presentation of biochemical factors
c. Porous environment for diffusion of nutrients, metabolic by products and waste
d. Mechanical rigidity or flexibility
Some methods used in regenerative medicine do not involve utilising living cells prior to implantation of the scaffold/material. These methods rely on the host cells to migrate into the scaffolds. Cells exhibit the ability for directional migration, and this is dependent on the concentration gradient of bioactive signalling molecules present. Different types of cells encounter different obstacles dur...
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...o biological polymers are synthetic ones. Polymers such as polyfumarates and polylactic acid can be processed to form a range of 3D scaffolds with variable network structures/porosities and surface characteristics. Hydrogels are also a form of polymer and will be further described in a later section. They are popular due to its minimally invasive implantation and ability to gel in situ, providing a 3D cellular microenvironment with high water content (Stevens, 2008).
Bone has a composite nature, made up of both organic and inorganic components. As such, composite materials like HA-collagen nanocomposite systems aim to combine the toughness of polymers and the strength of inorganic materials. Despite the promising results, current composites are still mechanically inferior to that of real bone, as recreating the nanoscale order in organization of bone is difficult.