Any medical device implanted in the body or in contact with flowing blood faces two critical challenges that can threaten the life of the patient the device is meant to help: blood clotting and bacterial infection. But, a team of scientists at the Wyss Institute for Biologically Inspired Engineering at Harvard, Boston, say they may have a solution. The researchers have developed a new surface coating for medical devices using FDA-approved materials. The coating not only repelled blood from more than 20 medically relevant substrates the team tested, but also suppressed biofilm formation. And, the team’s implanted medical-grade tubing and catheters coated with the material prevented blood from clotting for at least eight hours without the use of blood thinners such as heparin.

This scanning electron microscope image shows how red blood cells coagulate to form a blood clot. (Credit: James Weaver, Harvard’s Wyss Institute)

The idea for the coating evolved from Slippery Liquid–Infused Porous Surfaces (SLIPS), a pioneering surface technology developed at Harvard. Inspired by the carnivorous pitcher plant, SLIPS repels nearly any material it contacts. The liquid layer on the surface provides a barrier to everything from ice to crude oil and blood.

The Wyss team developed a super-repellent coating that can be adhered to existing, approved medical devices. In a two-step surface-coating process, they chemically attached a monolayer of perfluorocarbon. Then they added a layer of liquid perfluorocarbon, which is widely used in medicine for applications such as liquid ventilation for infants with breathing challenges, blood substitution, eye surgery, and more. The team calls the tethered perfluorocarbon plus the liquid layer a Tethered–Liquid Perfluorocarbon surface, or TLP for short.

In addition to working seamlessly when coated on more than 20 different medical surfaces and lasting for more than eight hours to prevent clots in a pig under relatively high blood flow rates without the use of heparin, the TLP coating achieved the following results:

  • TLP-treated medical tubing was stored for more than a year under normal temperature and humidity conditions and still prevented clot formation
  • The TLP surface remained stable under the full range of clinically relevant physiological shear stresses, or rates of blood flow seen in catheters and central lines, all the way up to dialysis machines
  • It repelled the components of blood that cause clotting (fibrin and platelets)
  • When bacteria called Pseudomonas aeruginosa were grown in TLP-coated medical tubing for more than six weeks, less than one in a billion bacteria were able to adhere. Central lines coated with TLP significantly reduce sepsis from Central–Line Mediated Bloodstream Infections.