Newly developed artificial tissues have been approved for use in wound healing as well as for skin grafts. These artificial tissues are made by “seeding” cells into a bioengineered scaffold where upon they reorganize it into a material suitable for use as an artificial tissue. In the process of tissue engineering the cell makes use of the scaffold components as nutrients. The starting scaffold is usually three dimensional Jello like material called a collagen gel. Made up mostly of water, sugars, and carbohydrates the gel also contains fibrous proteins like collagen, fibrin, and fibronectin which allow the cells to interact with the scaffold. The fibrous proteins are large and tend to form bundles of fibers, or fibrils. After some time the cells use up the scaffold materials reorganizing some of them into an artificial tissue that can then be used for surgical procedures.

Because the tissue is grown from the patient's own cells, there is almost never any rejection of the transplant. In some cases, such as cancerous tissues, this is not possible. However, using compatible cells from an appropriate donor gives a high success rate with no risk to the cell donor. Further developments of tissue engineers have made it possible to replace not only tissues, but also organs. One such technology is tissue printing which would allow one to produce whole organs from gel scaffolding and cells in an ingenious way.

This advanced technique allows for cells to be arranged within the scaffold in order to shape the tissue into larger structures. Cells are arranged by inserting them into a device analogous to an inkjet printer where cells are ink. The cells are then printed in a two dimensional pattern such as a circle. After a circle of cells is laid down on top of a sheet of scaffold, another layer of scaffold is placed on top, followed by yet another circle of cells and another sheet of scaffold. Several circles placed in this way will reorganize the scaffold to form a tubular tissue, thus creating a tissue with a vascular system. This is one of the biggest breakthroughs in tissue engineering, because it allows blood and nutrients to flow through the artificial tissue. Tissue printing thus allows us to develop microstructures. These developments have lead to externally grown tissues which can replace vital organs, as well as more general tissues like skin, bone, muscles, and arteries. The lack of transplant materials is no longer a problem.

source...
http://cns.asu.edu/nanofutures