Gecko Stitches

Jeff Karp of Boston's Brigham and Women's Hospital and Harvard Medical School along with Massachusetts Institute of Technology's Bob Langer and others writing in the Proceedings of the National Academy of Sciences, have demonstrated a tape that during initial tests can be used internally. Like internal stitches, the tape is designed to eventually break down inside the body after the body heals.

The feet of the lizard-like gecko are not sticky in the same way a tape or a glue is sticky. Researchers have learned that the gecko's tacky little secret lies in nano scale hairs on the bottom of its feet. Karp says, "They're able to use these nanofeatures to attach to a surface." The hairs give the gecko more surface area of contact on a molecular level than what other animals or people have. Karp explains, "All materials are able to interact with another through creating a little bit more of a positive charge or negative charge on one side of the molecule versus the other, and this can cause very small levels of attraction between different materials. And so if you can increase the surface area of contact, you can make these types of interactions significant." This interaction among stable molecules is known as the Van der Waals force.

However under the wet conditions of surgery, this force breaks down, so the researchers created similar hairs that mechanically interlock with the tissue. "We look at this (as) more of (a) gecko-inspired adhesive than a gecko-mimicking adhesive," says Karp.

Still, by itself this interaction still isn't enough. As Karp points out, "If the gecko's feet were too sticky the gecko wouldn't be able to move at all …(but) the surgeon would want to be able to place this adhesive and then not have it move. So, it needs to be very stable." So, Karp says the researchers added a "thin layer of a biodegradable glue to the surface…(that)…significantly enhances the interaction of our adhesive with the tissue surface."

The research team, which included experts on everything from materials to surgery to, of course, gecko feet, is also developing the biodegradable glue. Karp says the glue "gave us the advantage of chemical cross-links with the tissue in addition to the mechanical interlocking that we get from these adhesives."

Karp says they have tested this tape "against intestinal tissue in the laboratory," but are continuing to tweak both the gecko inspired nanoscale features of the tape and the glue to see if they can improve even more on the gecko's tacky little secret.

Among the other experts on the team were surgeons from Massachusetts General Hospital, Draper Laboratories for the nano scale work, and polymer chemists from Massachusetts Institute of Technology for the special glue.