Researchers are investigating how a blood plasma protein changes structure at a stainless steel surface with a view to developing more biocompatible medical implants, including stents. 

Stents are often used in the treatment of coronary heart disease to hold open blood vessels that have become blocked. Typically these tubular devices are made of a biologically inert material such as stainless steel mesh; even so, blood clots can form on stent surfaces, which in turn can cause complications for patients. 

The clotting process is initiated by fibrinogen, a protein present in human blood plasma. In its native state fibrinogen is dissolved in blood and does not initiate clotting, but stainless steel surfaces adsorb the protein and clotting follows.

Marie-Josee Desroches and Sasha Omanovic, at McGill University in Montreal, Canada, used an advanced infrared spectroscopy technique to determine fibrinogen's structure when adsorbed onto a type of stainless steel used to make stents. Using polarisation-modulation infrared reflection-absorption spectroscopy,
the team found that the protein's secondary structure (the coiling and folding of the protein backbone) undergoes significant changes on adsorption, and that this structure change is crucial for clotting. The researchers were also able to quantify the degree of change in fibrinogen's structure. 

Omanovic said that he hopes the work will allow scientists to develop materials with surfaces that are less likely to cause blood clots making stenting a safer procedure. 'The ultimate goal of our research is to gain knowledge that will enable us to nano-engineer implant surfaces to precisely control protein-surface interactions,' he explained. 'This will allow us to regulate subsequent cell-surface interactions and ultimately the functionality of the implant.'

James Hodge