Artificial blood vessels

 Lightning helps create artificial blood vessels

Lightning bolts could help create artificial organs, according to new research by scientists at Texas A&M University.

An electrically charged block of plastic gives way to a series of tunnel-carving lightning bolts when a nail is driven into it. Adding human blood vessel cells to the tunnels could create a template upon which an artificial organ could grow.

"One of the biggest problems in tissue engineering is how to create a vascular network to feed the growing tissue," said Arul Jayaraman, a professor at Texas A&M who, along with his colleague Victor Ugaz, co-authored the study that appears in the journal Advanced Materials. "The structure of these networks closely resembles the human vasculature."

The artificial organs begin as clear blocks of biodegradable plastic about the size of an inch-thick stack of Post-It notes. An electron beam fills the block with electricity, then the scientists drive nails into either end of the plastic block.

With each strike of the hammer, lightning streaks through the block and exits through the nail, leaving tiny tunnels in its wake. "It's pretty spectacular," said Jayaraman. "It looks just like lightning bolts."

These tunnels are remarkably similar to the capillary system inside the human body. At their largest size, where the nails are driven in, the lightning induced tunnels are about the same size as veins and arteries. In the middle of the block, the tunnels are smaller, about the same size as capillaries.

The tunnels also connect with each other; fluid that goes in one side comes out the other. The streaking of the lightning might seem random, but it penetrates all areas of the block, ensuring an adequate blood supply to the entire organ.

The entire process takes only a few seconds. That's much faster and cheaper than previous efforts to create 3D artificial channels, said the researchers.

Traditionally, scientists create 3D channels in plastic using the same techniques used to produce computer chips, a technique known as photolithography.

A metal mask is place over a flat surface and the pores or channel are created by shining light onto the open areas. The flat layers would then have to be assembled one on top of another to create a 3D structure. The process is expensive and time-consuming.

"You have to build it one layer at a time," said James Landers, a scientist at the University of Virginia who builds 2D channels for sensing applications. "If they can get lots of pores in a 3D block by simply applying a voltage, that would be very interesting."

One big difference of the new technique is that the channels inside each plastic block are unique. The channels created by photolithography are almost completely identical.

Creating an identical vascular system for a kidney, for example, might not be necessary, said Landers.

Rosemarie Hunziker of the National Institutes of Health agrees. As long as all parts of the artificial organ are close enough to receive nutrients and eliminate waste, they don't need to be identical.

"If you took kidneys from five different people and sliced them open, you would not see the exact same vascular pattern, at the microscopic level," said Hunziker, "even though the overall structure would be the same."

Creating a block of what resembles frozen lightning is only a first step to growing new organs.

With a blood system, scientists can now work to implant cells that will become the actual blood vessels. Then the cells that would become the actual liver, kidney or heart would have to be implanted. As the cells grow, the plastic would harmlessly degrade, until only the organ remained.

It will likely be years before such an organ is implanted into animals, let alone humans, caution the scientists.

"This is very nice, very innovative work, but also very early stage work," said Hunziker. "Evolution produced this vascular system that we have for a reason. And what (the researchers) can do is not only create this vascular network that resembles natural morphology, they can do it in a way that is rapid and reproducible."

© 2011 Discovery Channel