Tuesday, February 19, 2008

Sticky Tape to Heal Surgical Incisions

Sheets of elastic, sticky polymers could replace sutures and provide long-term drug delivery.

By Katherine Bourzac

Tissue tape: A very sticky tape that could replace sutures is broken down in conditions that mimic the inside of the body (top). The tape, an elastomer covered with nanoscale pillars and biocompatible glue, is iridescent (bottom). Credit: Jeffrey Karp

Multimedia •  See another view of the tape.

Researchers at MIT have developed a stretchy, biodegradable tape that could replace surgical sutures and staples. The new sticky tape could also be made into drug-delivery patches for placement directly on organs including the heart. The tape, which has been tested in mice, slowly breaks down inside the body without causing any irritation.

The adhesive is inspired by geckos' feet, which allow the reptiles to walk along the ceiling and up and down smooth walls. Gecko toes are sticky because they are covered with millions of flexible nanopillars, giving them a very large surface area. The MIT tape, which relies on both nanoscale pillars and a chemical glue, is the first such tape to show good adhesive strength and safety in animals. It's being developed by Institute Professor Robert Langer and Jeffrey Karp, a bioengineer in the Harvard-MIT Division of Health Sciences, in collaboration with researchers at two Boston hospitals.

The tape is made of a biodegradable elastomer that can be laced with drugs. To make the adhesive, the liquid polymer is poured into microfabricated silicon molds pocked with 200-to-500-nanometer-wide indentations. The molded, hardened polymer is then spin-coated with a biocompatible dextran glue. When the tape is applied, capillary forces pull tissue into the spaces between the pillars, which also have some weak charge attractions; the dextran glue adheres to tissue proteins.

It's a "really strong" adhesive, says Metin Sitti, associate professor of mechanical engineering at Carnegie Mellon University.

Making gecko tape that's safe and effective for medical use has been challenging, says Sitti. Most gecko-inspired adhesives--like those designed to help robots scale walls--are engineered to work on smooth, hard surfaces. For these kinds of applications, it's important that the tape be reusable. Medical tape like Karp's needs to stick only once, but stick strongly. Getting high adhesive strength on tissues is hard to do, since they are "wet, soft, slippery, [and] rough," says Sitti.