Researchers developed a 3D artificial capillary system using a technique inspired by a conventional cotton candy machine. The artificial capillary system is capable of keeping cells alive and functional for more than a week.

Mechanical engineering assistant professor Leon Bellan from Vanderbilt University has been studying cotton candy machines and trying to get these to create tiny networks of threads whose size, complexity and density are similar to the ones created by capillaries. The goal is to make fiber network templates that can be used to create capillary systems of life-sized artificial organs.

Laboratories use thin sheets of hydrogels to grow cells. These water-based gels deliver nutrients and remove waste well, but only if they are very close to a nutrient and oxygen source as well as a "sink" for the waste produced. Creating a capillary network that can support thicker tissues is another story, which means scientists need to create a highly complex network of very fine channels. This inspired lead author Bellan to buy a conventional cotton candy machine from Target for about $40 to create the very fine channels he needed.

The researchers built a machine that works like a normal cotton candy machine, but instead of spinning out very fine threads of sugar, it spins Poly(N-isopropylacrylamide) or PNIPAM, a type of polymer. The machine creates ultra-fine clouds of PNIPAM.

A solution that contains human cells is then poured over the PNIPAM clouds. The PNIPAM structure is allowed to gel inside an incubator at 37 degrees. A common food industry enzyme called transglutaminase allows the structure to permanently gel.

The incubated structure is then cooled at room temperature. When the embedded fibers dissolve, it leaves highly complex micro channels. Pumps are then used to suffuse the network with the necessary oxygen and chemicals.

"Our experiments show that, after seven days, 90 percent of the cells in a scaffold with perfused microchannels remained alive and functional compared to only 60 to 70 percent in scaffolds that were not perfused or did not have microchannels," says Bellan. The researchers added that the goal is to come up with a basic "tool box" that other research teams can use to create capillary systems required for artificial organs.

"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," notes Bellan, saying that some experts in the field thought the method was a little crazy.

The research was published in the journal Advanced Healthcare Materials on Feb. 4.

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