A new recipe for artificial blood vessels may help solve a tough clogging problem
Posted October 31, 2006on:
Small, artificial blood vessels are meant to offer hope to cardiac-bypass patients. The problem is that these tiny synthetic vessels tend to clog. Now, biomedical engineer Donald Elbert and his team at Washington University, in St. Louis, have developed a new material designed to trick the body into building vessels from its own cells.
The root of the clogging problem is thermodynamics, Elbert says. When a vessel is made of modified Teflon–or anything besides the body’s own cells–clotting proteins in the blood bump into the vessel walls, stick, unfold, and become active, setting off clotting reactions. The clots are too small to block large vessels, and in fact, Teflon aortas are common. But in vessels narrower than six millimeters across, clots make clogs. Consequently, cardiac-bypass patients can’t receive small artificial-vessel implants. Instead, small vessels have to be harvested from the patient’s body so that blood can be rerouted. This is an extra surgery, and eventually, the patient may run out of vessels to harvest.
Elbert’s solution is a novel coating for the inside of artificial vessels. It’s primarily made of substances found in the human body. Polyethylene glycol, the only synthetic ingredient, is a many-armed polymer used in toothpaste and shampoo. When exposed to blood, it repels nearly all clotting proteins that try to stick to it. Albumin, a blood protein, is included to attach polyethylene glycols together. Polyethylene glycol’s arms link to two biologically active ingredients. One of the ingredients is a protein fragment that acts like Velcro, binding endothelial cells, which line human blood vessels, to the artificial lining. The other bioactive ingredient is an enzyme found in blood that can grab a fatty substance, or lipid, from the bloodstream and convert it into a lipid called sphingosine-1-phosphate that sends growth and survival signals to endothelial cells.
Read rest of this fascinating story at MIT Technology Review
Source: MIT Technology Review