Slippery When Coated: Helping Medical Devices Prevent Blood Clots

A carnivorous plant has inspired an invention that may turn out to be a medical lifesaver.

Nepenthes, also known as tropical pitcher plants or monkey cups, produce a superslippery surface that causes unfortunate insects that climb into the plant to slide to their doom.

Scientists at Harvard's Wyss Institute for Biologically Inspired Engineering wondered if they could find a way to mimic that surface to solve a problem in medicine.

The medical problem is blood clots. Whenever blood flows over an artificial surface, whether it's an implanted pacemaker or the tubing that blood flows through on the way to a dialysis machine, there's an increased risk that a dangerous clot will form.

To prevent this, doctors often turn to blood thinning medicines such as Coumadin. But these medicines can also cause their own problems, such as brain bleeds.

The Harvard scientists wondered if they could find a coating that would have the same properties as the nepenthe's slippery surface; something that could be applied to tubing or devices that come in contact with blood.

As they report in the journal Nature Biotechnology, they tested man-made materials known as perfluorocarbons, searching for one that would have the same characteristics as the nepenthe's coating. As luck would have it, they found one called perfluorodecalin which was already being used in medical applications.

Blood on a non-coated surface and blood on a perfluorocarbon-coated surface.

Credit: Wyss Institute at Harvard University

The researchers tested the coating in pigs. They diverted blood coming from a pig's heart through a loop of tubing before returning it the pig's blood supply. They compared tubes with the new coating, and without. Blood flow through the coated tubes remained virtually constant over the 8 hours of the experiment, whereas clots formed in tubing without the coating, substantially slowing blood flow with time.

The Harvard group isn't the only one tackling the clotting problem. The Sorin Group and Medtronic are also testing coatings that keep blood from clotting. Donald Ingber, founding director of the Wyss Institute and senior author on the Nature Biotechnology paper says he is looking for an investor or partner to further develop the substance.