This award to University of Kentucky by the Biomaterials program in the Division of Materials Research is to study the use of antigenic protein disguise to create biocompatible surfaces on blood-contacting medical devices. Clinical uses of blood-contacting devices are becoming more common. While many of these devices have been successfully used in patients for many years and are judged to be therapeutically beneficial, their performance is less than optimal. Upon implantation, some of these devices become completely coated with proteins and lead to formation of thrombi, which can cause significant problems. With this award, the PI will study binding of a bacterial protein called Tp0483 with human plasma fibronectin to create a hemocompatible surface by utilizing this as an antigenic disguise. The overall objective of this investigation is to study surface modifications by bacterial proteins called Tp0483, which as antigenic protein disguise may have potential applications in hemocompatible surfaces and systems. Earlier studies have shown that this bacterial protein binds with soluble dimeric fibronectin and the bound fibronectin serves an antigenic disguise for the bacterium. In this study, Tp0483 will be adsorbed to surfaces using self-assembled monolayer and the adsorption of fibronectin (FN) and a fibronectin fragment FN 7-10 will be investigated using surface plasmon resonance. In addition, the mechanism of adsorption of the FN and FN 7-10 to the Tp0483 will be studied using Atomic Force Microscopy (AFM) to determine binding strength of these proteins.
Earlier, many different approaches have been used to create blood-compatible surfaces and while these processes have been shown to improve blood-compatibility, the creation of a wholly hemocompatible surface has, thus far, been unachievable. In this study, antigenic disguise will be used to create hemocompatible surfaces on implantable medical devices, and if successful, would have high impact in the use of these devices. In addition, information obtained on mechanisms of fibronectin binding to the bacterial protein TP0483 will provide a better understanding as to how the bacteria uses this protein for antigenic disguise. While this study focuses specifically on using the protein, Tp0483 for improving compatibility of blood-contacting materials, the results will form the basis for future studies where other naturally occurring proteins known for antigenic disguise can be studied. This award will provide graduate, undergraduate and high school students will opportunity to participate in this research and receive multidisciplinary training in engineering and materials science.
Clinical uses of blood-contacting devices are becoming more common. While many of these devices have been successfully used in patients for many years and are judged to be therapeutically beneficial, their performance is less than optimal. Almost immediately upon implantation in the body, blood-contacting materials become completely coated with proteins and this leads to attachment of cells in the body. Aggregated platelets combine with protein on the surface and lead to formation of thrombi which can cause significant problems downstream and also hinder the performance of the device. The overall objective of this investigation was to test the feasibility of using a protein found on the surface of a bacterim, Treponema pallidum protein, Tp0483 bound to human plasma fibronectin to create a hemocompatible surface by utilizing antigenic disguise. In this study, it was hypothesized that FN would bind to the Tp0483 protein through a binding site on the FN called RGD. This binding site is responsible for adhesion of blood proteins and cells and hence, if it is used to bind to the Tp0483, it would be hidden and blood proteins and cells would then be inhibited from binding. Also, it was hypothesized that inhibition of binding of blood proteins and cells will occur due to the body recognizing the FN coated surface as a natural, physiological system. Because of these binding properties, it was hypothesized that the Tp0483/FN could serve as an antigenic disguise for the surface. This study demonstrated that RGD binding sites on FN are responsible for FN binding to the protein fragment, Tp0483. We also demonstrated that blood proteins were partially inhibited from binding to surfaces that included the Tp0483/FN complex. In addition, it was demonstrated that platelet activation was also decreased when exposed to these surfaces. This study demonstrates that the Tp0483/FN complex could be used on surfaces to improve biocompatibility. Continued studies are focusing on the adsorption of the proteins on a polymer network with specific applications as post-surgery adhesion barriers. As demonstrated in the Figure, protein such as fibrin and calls can attach to one side of the polymer network but the other side containing the Tp0483/FN complex would inhibit binding. This would allow tissue to heal after surgery without the formation of post-surfical adhesions. Two graduate students worked on this original project and both students have graduated with their Ph.D. degrees. Dr. Morgan Abney is currently a Research Scientist at NASA Marshall Space Flight Center in Huntsville AL and was awarded the 2011 Presidential Early Career Award For Scientists and Engineers. Dr. Matt Dickerson was recently awarded a postdoctoral fellow in the NIH/NCI Cancer Nanotechnology Training Center (CNTC) at the University of Kentucky. In addition, three undergraduate students were involved on this project. One of these undergraduates received 3rd place in the Univ. of Kentucky Chemistry’s Department Multi-School Research Competition. Three manuscripts have resulted from this project; 1 published and 2 submitted.
