The same technology used to create fluffy, gooey fibers of sweet goodness may hold the key to the creation of artificial organs. Instead of spinning out cotton candy, however, scientists are now using them to successfully produce a three-dimensional capillary system that can keep living cells viable and functional.
Leon Bellan, assistant professor of mechanical engineering at Vanderbilt University, announced in an article this week in the Advanced Healthcare Materials journal that he has been spinning out networks of threads comparable in size, density and complexity to those comprising capillaries. Capillaries are the small vessels that deliver nutrients and oxygen to cells and remove waste. His goal is to create fiber networks that can be used as templates to produce capillary systems needed to make artificial organs for transplant.
His idea to use a cotton candy machine came about when he was in graduate school and researching electrospinning, using strong electric fields to create nanofibers.
The analogies everyone uses to describe electrospun fibers are that they look like silly string, Cheese Whiz or cotton candy. So I decided to give the cotton candy machine a try. I went to Target and bought a cotton candy machine for about $40. It turned out that it formed threads that were about a tenth of a diameter of a human hair – roughly the same size as capillaries – so they could be used to make channel structures in other materials.
Ballan and other researchers are also working with hydrogels, water-based gels, to support cells within three-dimensional artificial organs. Hydrogels mimic the natural extracellular matrix (the structure that holds the capillaries) that surround cells in the body. The goal is to create tissues that have the thickness of real organs with the ability to allow fluids to flow through like the natural capillary system.
In order to create artificial capillaries, the right formula to create a network of fibers that would not dissolve in the hydrogel, had to be found. Ballan and his colleagues experimented with a number of materials before settling on PolyNisopropylacrylamide (PNIPAM), used safely in other medical products. The PNIPAM is insoluble in water when made in a mold, and doesn’t dissolve when the gel is poured. Then, it dissolves in water to create the microchannel, since cells will only grow in an aqueous environment.
Some people in the field think this approach is a little crazy. But now we’ve shown we can use this simple technique to make microfluidic networks that mimic the three-dimensional capillary system in the human body in a cell-friendly fashion. Generally, it’s not that difficult to make two-dimensional networks, but adding the third dimension is much harder; with this approach, we can make our system as three-dimensional as we like.
The researchers’ next step is to perfect the capillary system with different types of human tissue in order to grow complete artificial organs like the kidney, liver or solid bone.
What started as a machine making county fair treats may someday take science one step closer to the creation of the Bionic Man or Bionic Woman.