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Bio-Inspired Coating for Medical Devices Repels Blood and Bacteria

Harvard discovery could help prevent clotting and infections

A team of Harvard scientists and engineers has developed a surface coating for medical devices that may help prevent blood clotting and bacterial infection when those devices are implanted in the body or in contact with flowing blood.

The new surface coating, which uses materials already approved by the FDA, repelled blood from more than 20 medically relevant substrates the team tested — ranging from plastic to glass and metal — and suppressed biofilm formation, according to an article published in Nature Biotechnology.

When the team implanted medical-grade tubing and catheters coated with the material in large blood vessels in pigs, it prevented blood from clotting for at least 8 hours without the use of blood thinners, such as heparin. Heparin is known to cause potentially lethal side effects, such as excessive bleeding, but it must often be used in treatments where clotting is a risk.

“Devising a way to prevent blood clotting without using anticoagulants is one of the holy grails in medicine,” said senior author Don Ingber, MD, PhD.

The idea for the coating evolved from slippery liquid-infused porous surfaces (SLIPS), a pioneering surface technology developed by coauthor Joanna Aizenberg, PhD. Inspired by the slippery surface of the carnivorous pitcher plant, which enables the plant to capture insects, SLIPS repels nearly any material it contacts.

“Traditional SLIPS uses porous, textured surface substrates to immobilize the liquid layer, whereas medical surfaces are mostly flat and smooth — so we further adapted our approach by capitalizing on the natural roughness of chemically modified surfaces of medical devices,” Aizenberg said.

The researchers 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, which is similar to Teflon. They then 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, and eye surgery. The team calls the tethered perfluorocarbon plus the liquid layer a tethered-liquid perfluorocarbon (TLP) surface.

In addition to working when coated on more than 20 different medical surfaces and lasting for more than 8 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 1 year under normal temperature and humidity conditions and still prevented clot formation.
  • The TLP surface remained stable under the full range of clinically relevant physiologic shear stresses, or rates of blood flow seen in catheters and central lines, all the way up to dialysis machines.
  • The TLP surface repelled the components of blood that cause clotting (fibrin and platelets).
  • When Pseudomonas aeruginosa bacteria were grown in TLP-coated medical tubing for more than 6 weeks, less than one in 1 billion bacteria were able to adhere. Central lines coated with TLP significantly reduced sepsis from central-line–mediated bloodstream infections.

While most of the team’s demonstrations were performed on medical devices, such as catheters and perfusion tubing using relatively simple setups, they say there is more on the horizon. “We feel this is just the beginning of how we might test this for use in the clinic,” said co-lead author Daniel Leslie, PhD, who aims to test it on more complex systems.

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