An investigation of the effect of surface released nitric oxide on fibrinogen adsorption
Lantvit, Sarah Marie, author
Reynolds, Melissa, advisor
Borch, Thomas, committee member
Fisher, Ellen, committee member
Kennan, Alan, committee member
Popat, Ketul, committee member
The search for improved biomaterials is a continually ongoing effort to prevent the failure of medical devices due to blood clotting. Each group of researchers has their own set of methods to create the ideal material for biological systems. In the pursuit of materials to prevent blood clot formation, these attempts have been focused on alterations in surface properties, pre-adsorption of proteins, and release of drugs. In this work I took a high-throughput approach to the prevention of device failure by investigating a model material system. Starting with a nitric oxide (NO) releasing material, a sample preparation method was developed to ensure that surface properties could be compared to a non-NO releasing control. With this material, the effect of the NO release on fibrinogen adsorption to these surfaces could be isolated. Fibrinogen is instrumental in the formation of blood clots. Determining the effect that NO has on this protein will help determine why NO has been previously found to prevent clotting in blood-contacting systems. Once the model system was developed, further investigation into changes in the fibrinogen resulting from its interaction with the released NO could be undertaken. A full investigation was completed on control non-NO releasing, low NO flux, and high NO flux materials. A qualitative assessment of the fibrinogen adsorption shows that the high NO releasing material exhibits significantly higher fibrinogen adsorption compared to both the control and low NO flux materials. Quantitative assessment of fibrinogen adsorption was attempted through a variety of methods, which indicate that conformational changes are happening upon adsorption of fibrinogen to all materials. To this end, FTIR spectra from the adsorbed fibrinogen and native fibrinogen were compared to elucidate changes in the protein's conformation. Control and low NO flux materials had too little protein to gain insight into these changes. For the high NO flux material, the fibrinogen had a significant decrease in α-helices and an increase in random chains compared to native fibrinogen. To begin understanding the effect that these changes will have on blood clot formation, these materials were further analyzed for platelet adhesion. A comparison of the control, low NO flux, and high NO flux materials with and without fibrinogen adsorbed to the material surface shows that the fibrinogen has a distinct effect on platelet adhesion and aggregation. The high NO flux materials exhibited less aggregation and full activation of platelets when fibrinogen was adsorbed prior to incubation with platelets than if fibrinogen was not present before incubation. Overall, the effect of NO on fibrinogen adsorption can be seen through these measurements. Nitric oxide release causes an increase in fibrinogen adsorption, as well as protein reorganization. Surprisingly, we see that this adsorbed fibrinogen actually improves the viability of platelets. Further study must be done using whole blood and in vivo measurements to fully understand what effect the adsorbed fibrinogen will have on the device. Despite this we can say that the adsorption of fibrinogen onto these NO releasing materials helps to improve the biocompatibility of this biomaterial due to its bulk adsorption and conformational changes.