This image - from implanted mice - shows how a teflon surface coated with SLIPS does not attract infectious bacteria, red blood cells, immune cells, or extracellular matrix material.
Image credit: Wyss Institute at Harvard University
The researchers, including a team from the Wyss Institute at Harvard University in Boston, MA, report their findings in the journal Biofilms.
Biofilms form when bacteria stick to surfaces and establish communities held together by a slimy, glue-like substance made of sugary molecular strands that they excrete to form an extracellular matrix.
Biofilms grow on all kinds of surfaces, both natural and man-made. Essentially, wherever moisture, nutrients, and a surface are found together, you will most likely also find biofilm.
The study of biofilms has increased rapidly in recent years as we have become more aware of their pervasiveness and impact. The equipment damage, product contamination, energy losses, and medical infections caused by biofilms cost the United States billions of dollars every year.
In medicine, biofilms are a hazard because they can form on living surfaces, such as heart and lung tissue, and on medical devices and implants. Once established, they cause infections that are hard to treat. They also contribute to the rise in antibiotic-resistant infections seen in hospitals.
SLIPS surface coatings repel range of substances
The new study describes a novel biomaterial made from medical-grade teflon materials and liquids. It is based on the concept of "slippery liquid-infused porous surfaces," or SLIPS, developed by co-senior author Joanna Aizenberg, a Harvard professor of chemistry and chemical biology.
Prof. Aizenberg got the idea for SLIPS from observing how the carnivorous pitcher plant catches insects on the slippery surfaces on its leaves - by using their porous surfaces to immobilize a layer of liquid water.
The idea of SLIPS has already led to surface coatings that can repel a range of substances such as ice, crude oil, and biological materials.
Prof. Aizenberg says they are applying the concept of SLIPS to medical applications by fine-tuning the chemical and physical features of medical-grade materials and the infused lubricants.
SLIPS applications in medicine already include coatings that repel bacteria and blood from small medical implants and instruments. More recently, they have also helped keep the lenses of endoscopes and bronchoscopes free of fluids so clinicians can see what they are doing.
SLIPS resisted biofilms and preserved immune response
In the new study, the team started with lab tests to find the teflon material that would best work with a selection of lubricants to make a long-lasting coating to repel a common strain of bacteria that infects medical implants.
Another important requirement was that the material must not disrupt the normal anti-bacterial immune response.
The best performing material was "expanded polytetrafluoroethylene" (ePTFE) - which is used in implants for a wide range of reconstructive surgery, including prosthetic grafts for cardiovascular reconstruction and mesh for hernia repair. They found the material tested well with lubricants with proven acceptable safety profiles.
In another set of experiments, the researchers compared the performance of implanted hernia meshes with and without SLIPS in live rodents. They measured the bacterial and tissue responses to the implants after infecting the animals with Staphylococcus aureus, a common bacterium found in biofilms.
The researchers found the SLIPS coating performed very favorably. Implanted ePTFE mesh coated with SLIPS resisted infection by bacteria, and showed much less infiltration by immune cells and inflammation than implants made of non-coated ePTFE mesh.
"Here we have extended our repertoire of materials classes and applied the SLIPS concept very convincingly to medical-grade teflon, demonstrating its enormous potential in implanted devices prone to bacterial fouling and infection."
Prof. Joanna Aizenberg