3-D printing is based on the same technology as that used by an inkjet printer to print a page of text, but instead of working in two dimensions, the printer is working in 3 dimensions, building up layers as it goes. In the case of inanimate objects a substance such as plastic is loaded into the printer along with a 3-D design of the object to be produced, for example, a toy action figure. The printer follows the design, printing layer after layer of plastic until a solid object is formed. In the case of 3-D bioprinting human cells are multiplied in a Petri dish, forming a "biological ink" which along with other materials is loaded into a printer that uses the same layering process to produce the desired biological part.
Mike Titsch, Editor-in-Chief of 3-D Printer World said, "The mechanical process isn't all that complicated. The tricky part is the materials, which are biological in nature. It isn't like 3-D printing of plastic or metal. Plastic doesn't die if you leave it sitting on an open-air shelf at room temperature for too long." Cells may die before the printed tissue gets off the printer table. A vascular system is needed to provide the printed body part with oxygen and nutrients.
Organovo, a San Diego-based bioprinting company has made progress in solving this problem. They have been able to bring together fibroblasts and endothelial cells to develop tiny vascular networks, allowing them to create liver tissue with a thickness of more than 500 microns (about the thickness of five sheets of paper) that remains functional for at least 40 days.
But, other challenges remain. Much is not known about how tissue is formed at cellular and sub-cellular levels. About 40 different cell types with various functions are found in the human liver. Jordan Miller, Assistant Professor of Bioengineering at Rice University says "It's a complicated challenge. We don't know all the structures of the body. We're still learning. So, we don't know to what extent we need to reconstitute all those features. We have some evidence that we may not need to recreate all those functions." He believes that even if a portion of tissue produced is not complete it may continue to grow into a fully-functioning organ after being implanted in the body.
In the U.S. alone, about 120,000 people are on organ waiting lists. So, being able to print organs on demand would certainly be an amazing and welcome accomplishment, especially since worries about rejection would disappear as the organs could be based on a patient's own cells. But, due to the technical and regulatory hurdles in the way, other types of bioprinted parts are likely to become common much sooner. For example, thin layers of human tissue that mimic the function of various organs can be placed on microchips that are connected with a blood substitute that keeps the cells alive, allowing scientists to use them for drug testing. This process is known as creating "organs on a chip," and could be an alternative to using animal testing and Petri dishes, allowing new drugs to be developed faster and at a lower cost. 3-D printing could also be used to produce skin grafts which are now produced by the difficult process of manually laying down cells. 3-D printing could automate this process and make it exact and repeatable.
Some strange applications of 3-D bioprinting are also starting to appear. Dutch artist, Diemut Strebe, along with a team of scientists, has printed a reconstruction of Vincent Van Gogh's severed ear using cells taken from the great-grandson of Vincent's brother Theo. Should you find yourself in Karlsruhe, Germany, drop into The Center for Art and Media and take a look at it.