Blood clotting (thrombosis) is a constant hazard when blood is removed from its natural environment or disrupted during its flow within the body. It is known that the addition of citrate to blood samples assists in the prevention of clot formation. There is, however, some question as to the mechanism of citrate in clot prohibition. The most common hypothesis is that citrate operates by sequestering calcium ions known to promote the transformation of prothrombin to activated thrombin, which is required for clotting to proceed.

An alternate compound, heparin, has also found use in the prevention of thrombosis. It has been proposed that the action of heparin within surface coatings may mirror the action of free citrate, although the possibility exists that there are additional anti-thrombic mechanisms available to heparin. Heparin has become widespread as a surface coating for medical devices. It is derived from animal sources (pig intestine and cow lung), and is therefore less attractive for use with humans than citrate, which is present in all forms of life.

The purpose of this study is to provide a reliable and quantifiable procedure for creating citrated surfaces using amide bonding on microspheres. These microspheres will be characterized for their anti-thrombic abilities relative to spheres that possess generic positive and negative surface charges. If the results are promising, additional testing may be performed to directly determine the feasibility of citrated surfaces as a possible replacement for the current heparin coated medical devices.