Feb 10, 2016 | By Benedict
A day out at the carnival usually consists of three key events: Sharing a romantic moment on a ferris wheel, unsuccessfully attempting to win an oversized plush toy, and stuffing oneself with cotton candy. According to an article published in Advanced Healthcare Materials, one of these fair favorites could hold the secret to the production of artificial human organs: Leon Bellan, an assistant professor of mechanical engineering at Vanderbilt University in Nashville, Tennessee, used a $40 cotton candy machine from Target to develop a new method for creating artificial human capillaries.
Bellan’s medical repurposing of the candy-spinning utensil is not as crazy as it first sounds. Human capillaries, each around 10 microns wide, deliver oxygen and nutrients to cells, also serving to transport waste. The fabrication of artificial capillaries could prove to be an important element of 3D printed organ production, since these capillaries can support cells and encourage tissue growth. The most common method of artificial capillary production is “electrospinning”, but electrospun fibers are around ten times wider than their human counterparts.
Cotton candy machines, rarely seen in the laboratory, melt down sugar before squeezing it out through small holes in a spinning centrifuge, where the sugar hardens into strands. It has been remarked within the scientific community that electrospun fibers closely resemble these cotton candy strands; after thinking about this resemblance, Bellan thought: Why not attempt to create capillary-like fibers using the machine that produces their sugary doppelgänger?
"The analogies everyone uses to describe electrospun fibers are that they look like silly string, or Cheese Whiz, or cotton candy," Bellan told Vanderbilt News. "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 one tenth the diameter of a human hair—roughly the same size as capillaries—so they could be used to make channel structures in other materials.”
Unfortunately, sugar structures were unsuitable for cell growth, since pouring cell-filled hydrogels on the spun fibers would have dissolved them. Instead, Bellan and his team spun a polymer called Poly (N-isopropylacrylamide) or PNIPAM on a new device inspired by the cotton candy machine, creating a gelatinous cube of artificial capillaries. A solution of human cells in hydrogels was then poured over the PNIPAM structure at a temperature of 98.6 degrees fahrenheit.
The beauty of the PNIPAM fibers lies in their insolubility at temperatures above 89 degrees. The cotton candy-like structure remained solid as the cells were introduced, but completely dissolved when the temperature was reduced below that magic 89 degree mark, leaving a network of hollow channels within the cell cluster. Oxygen and nutrients could then be pumped through these channels, just like in real capillaries.
Bellan was able to keep the living cube of stringy stuff alive for over a week, longer than would have been possible using other more established techniques. 90% of the cells in a scaffold with the microscale channels remained alive and functional, compared to 60-70% in scaffolds that did not use the spun fibers.
"Some people in the field think this approach is a little crazy," said Bellan. "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.”
Next time you visit the local fair, think about how your delicious snack might have paved the way for 3D printed organ development. The full findings of the study can be found at the Wiley Online Library.
Posted in 3D Printing Application
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