Biomedical engineers at Washington University in St. Louis have found a new role for the blood protein serum amyloid P in the body's response to medical materials, which may help to explain a variety of problems associated with heart-lung bypass, hemodialysis and the use of artificial vascular grafts.
Using a technique called proteomics, the researchers identified many of the blood proteins that stick (adsorb) to the surfaces of medical devices. Blood proteins that adsorb to the surfaces of materials unfold and can be recognized by the body, which then mounts a response against the device. The body's response to adsorbed proteins contributes to a variety of problems, including the formation of small clots that may close off small diameter vascular grafts or break away to end up in the lungs, kidney or brain.
Previously, the study of blood proteins on the surfaces of medical devices has been limited by the large number of unique proteins in the blood -- greater than 150 -- as well as the extremely small amounts of proteins adsorbed on the materials. For example, the amount of protein that might adsorb to one side of a quarter is about a millionth of a gram.
Donald Elbert, Ph.D., Washington University assistant professor of biomedical engineering, used advanced protein separations and mass spectrometry to track the proteins on the surfaces of various polymers used in medical devices. The analysis techniques, collectively called 'proteomics,' are most often used to study protein expression in cells.
"The techniques are extremely sensitive and are really well-suited to studying proteins on surfaces," said Elbert. "Using these techniques, we can in principle identify a protein given only a billionth of a gram of the protein, even if the protein were mixed with many other types of proteins."
Elbert and his colleagues Jinku Kim and Evan Scott were able to follow the adsorption of multiple blood proteins on the surface of a biomaterial over time.
"Traditionally, most studies were limited to the 'big three' proteins in blood - albumin, fibrinogen and IgG", Elbert said. The results were published in the Oct. 1, 2005 issue of the Journal of Biomedical Materials Research.