Way back in 1912, French surgeon Alexis Carrel was awarded a Nobel Prize for developing a method of reconnecting blood vessels during surgery. His technique was very straightforward: he simply sewed them together.
The last 100 years have seen very few revisions to the suture-method of vessel connection. But now, doctors and engineers at Stanford University have developed a way to join blood vessels more quickly, safely, and easily — all without sutures.
In lieu of sutures, this new method uses a curious gel called poloxamer 407. Poloxamer 407 is not your typical polymer. Technology Review's Alla Katsnelson explains:
The trick was to tweak the properties of [poloxamer 407] so that it changes from a liquid to a solid state a few degrees above body temperature. The group used a halogen lamp to heat up the area around a severed blood vessel in rats, added the poloxymer, and then sealed the two ends with surgical glue.
That's right, at normal body temperatures poloxamer 407 exists in a liquid state, but heat it up a few degrees, and it becomes a solid. In the picture up top, you can see the polymer in its solid, heated state peeking out the ends of two latex tubes.
"The liquid turns into a solid, and then instead of a bunch of collapsible floppy pieces of linguine, you have something like pixie sticks," explains surgeon Geoffrey Gurtner, who collaborated with Stanford chemical engineers and biomaterials experts to tweak the properties of poloxamer 407, refine the sutureless technique, and demonstrate its efficacy in rats. After connecting the vessels, Gurtner says, "you're left with a scarless joint between the two blood vessels."
This diagram, from the researchers' article, demonstrates how by heating and cooling the poloxamer the researchers were able keep treated vessels dilated and aligned while they were being joined together (click to magnify). After the vessels are joined and return to 37C, the biocompatible poloxamer 407 is simply carried away via the vessels, to be excreted by the kidneys.
Images via Nature Medicine