Amyloid P Promotes Binding to Plastics

Researchers studying how the body responds to materials used in the manufacture of implanted medical devices have determined that serum amyloid P protein binds to plastic materials and induces adhesion and activation of leukocytes.

Investigators at Washington University (St. Louis, MO, USA) used gel electrophoresis, ion trap mass spectrometry, and other advanced proteomics techniques to study the binding of serum proteins to plastics such as polypropylene, polyethylene terephthalate (PET), or polydimethylsiloxane (PDMS) that are components of implanted medical devices.

They found that incubation of the plastic materials with 5% serum for longer than four hours resulted in binding of unexpectedly high amounts of serum amyloid P protein. Previous work had shown that serum amyloid P was constitutively expressed in humans, functioned as an opsonin (a molecule that acts as a binding enhancer for the process of phagocytosis), and interacted with receptors on leukocytes. In the current study, published in the October 1, 2005, issue of the Journal of Biomedical Materials Research, it was found that serum amyloid P adsorbed to polystyrene, PDMS, and PET under tissue culture conditions and promoted the adhesion of granulocytes and monocytes in the presence of calcium.

"No one had ever observed serum amyloid P on biomedical materials before, because, unless you were specifically looking for them, the technology was not around to easily identify proteins present in such small amounts,” explained senior author Dr. Donald Elbert, assistant professor of biomedical engineering at Washington University. "No one, including us, had ever posed the hypothesis that this protein might be important in the biocompatibility of materials. Our results show the importance of large-scale techniques that emphasize discovery of new knowledge, rather than just hypothesis-testing.”



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