Last month, Abiomed made news with the world’s first totally implanted artificial heart. The AbioCor replacement heart received approval from FDA under the Humanitarian Use Device provision, and will be used to extend the lives of patients who have no other alternatives.
More implantable devices like the AbioCor will follow, potentially saving or improving the lives of millions of people. According to various sources, the U.S. demand for implantables will increase as much as 10% annually through 2009. By then, the market is expected to reach about $33.8 billion.
Although all implantable devices aren’t as technically sophisticated as the AbioCor, they all face similar challenges when placed inside the body. A big problem with these devices has been life-threatening clots and bacterial infections. Cells and proteins build up on indwelling devices such as stents, urinary catheters, and dialysis tubing, and this can lead to product malfunctions, or blood clots or infections in patients.
Some implantable devices, such as stents, use coatings that elute drugs to prevent some of these situations. However, they aren’t foolproof. Recently, in an internal study, Boston Scientific found an increased risk of blood clots with its drug-coated cardiac stent, Taxus, compared with its earlier bare-metal stent.
Device manufacturers need to find a solution to these problems. The answers may lie under the sea among the creatures that live there. The common mussel produces a sticky glue that keeps it anchored to rocks and other objects. Chemical analysis of this waterproof glue has shown that the key to its stickiness is a compound called mussel adhesive protein. The protein contains a high concentration of an amino acid that can cling to wet surfaces with super strength.
Researchers at Northwestern University developed a two-sided coating from the mussel glue. One side is sticky, based on the adhesive proteins. The other is a special repellant. While the sticky side attaches securely to the surface of the implant, the repellant side prevents the build-up of cells and proteins.
“Our goal is to take advantage of the unique ability of mussels to attach to all types of surfaces, including Teflon, in order to develop a compound that will allow us to treat a variety of implant surfaces with a single approach,” says Phillip B. Messersmith, PhD, a professor in the biomedical engineering department at Northwestern.
Nerites Corp. (Madison, WI) saw the potential in the mussel glue and is developing it into commercial products called Medhesive and SurPhys. The company says the products could be on the market in two or three years.
Still other sea animals may be useful in improving implantables. A chemical compound found in crabs and shrimp fends off microbes seeking to colonize implantable medical devices, according to Montana State University researchers. Using the compound to coat these medical devices, they say, could help prevent thousands of bacterial and yeast infections annually.
In laboratory studies, chitosan—a sugar in the cells of crabs and shrimp—repelled bacteria and yeast. This substance prevents microbes from forming slimy, gluelike layers of infectious cells, known as biofilms.
That might not kill microbes outright, but it may discourage them from establishing a foothold, say the researchers.
Implantable devices are undoubtedly the wave of the future. Manufacturers need to find ways to make them even safer and more effective.