Small blood vessels are a great challenge in tissue engineering: both creating them in the first place in order to supply blood to constructed tissue, and then linking them into the body's existing blood supply when tissue is transplanted. The smaller the blood vessels, the harder this all becomes - so better ways of linking blood vessels together are necessary. "Reconnecting severed blood vessels is mostly done the same way today - with sutures - as it was 100 years ago ... Now, a team of researchers [has] developed a sutureless method that appears to be a faster, safer and easier alternative. In animal studies, a team [used] a poloxamer gel and bioadhesive rather than a needle and thread to join together blood vessels ... The big drawback of sutures is that they are difficult to use on blood vessels less than 1 millimeter wide. ... Sutures are troublesome in other ways, too. They can lead to complications, such as intimal hyperplasia, in which cells respond to the trauma of the needle and thread by proliferating on the inside wall of the blood vessel, causing it to narrow at that point. This increases the risk of a blood clot getting stuck and obstructing blood flow. In addition, sutures may trigger an immune response, leading to inflamed tissue that also increases the risk of a blockage. The new method could sidestep these problems. ... [Researchers used a] thermoreversible poloxamer called Poloxamer 407. It is constructed of polymer blocks whose properties can be reversed by heating. [They modified] the poloxamer so that it would become solid and elastic when heated above body temperature but dissolve harmlessly into the bloodstream when cooled. The poloxamer then was used to distend both openings of a severed blood vessel, allowing researchers to glue them together precisely. The researchers used a simple halogen lamp to heat the gel. In tests on animals, the technique was found to be five times faster than the traditional hand-sewn method, according to the study. It also resulted in considerably less inflammation and scarring after two years. The method even worked on extremely slim blood vessels - those only 0.2 mm wide - which would have been too tiny and delicate for sutures."