| AVS 58th Annual International Symposium and Exhibition | |
| Biomaterial Interfaces Division | Monday Sessions |
| Session BI-MoM |
| Session: | Biomolecules at Interfaces |
| Presenter: | Elaine Hillenmeyer, University of Washington |
| Authors: | E. Hillenmeyer, University of Washington O. Yakovenko, University of Washington R. Penkala, University of Washington W. Thomas, University of Washington D.G. Castner, University of Washington |
| Correspondent: | Click to Email |
von Willebrand Factor (VWF) is a soluble clotting protein responsible for binding platelets through the glycoprotein 1b platelet receptor. VWF can become activated and bind platelets when bound to collagen in an injured blood vessel or under increased shear.
VWF can also bind platelets when adsorbed to synthetic surfaces, specifically biomaterials. There is evidence that surface characteristics influence VWF adsorption. Previous AFM studies of VWF adsorbed to hydrophilic (mica) and hydrophobic (octadecyltrichlorosilane modified glass) surfaces showed differences in adsorbed topography1. However, studies were not performed to relate adsorption differences to VWF function.
Previous studies in our lab have shown differences in function and structure of the platelet binding domain of VWF (A1 domain) when adsorbed to three surfaces: polystyrene (PS), tissue culture polystyrene (TCPS), and glass, with A1 most active when adsorbed onto PS. A1 function was tested by measuring platelet binding under flow. A1 surface structure was investigated using time of flight secondary ion mass spectrometry (ToF-SIMS) and binding of conformation-dependent antibodies in ELISA assays.
In the work presented here, we have used surface analysis techniques to obtain greater detail about structural differences of the VWF A1 domain adsorbed onto synthetic surfaces. We used near-edge x-ray adsorption fine structure (NEXAFS) to examine the amide backbone, corresponding to the pi* feature of the nitrogen edge NEXAFS spectrum. Differences were observed in the angle dependence of the spectra when A1 was adsorbed onto PS, TCPS, and glass, indicating significant structural differences in the protein when adsorbed onto different surfaces. Sum Frequency Generation (SFG) was also used to probe the structure of the amide backbone using amide I spectra.
In addition to examining VWF on synthetic surfaces, we have used ToF-SIMS to obtain structural information about A1 bound to collagen, as occurs during in vivo injury. Principal component analysis of ToF-SIMS data showed differences between A1 bound to collagen and A1 adsorbed directly onto polystyrene. This suggests that A1 adopts different conformations on the natural versus synthetic substrates, potentially leading to different mechanisms of activation.
In this work, we use surface analysis tools to increase our understanding of VWF behavior, both on synthetic surfaces and in complex, layered protein systems. Increasing our fundamental knowledge of VWF can improve our understanding of VWF interactions with biomaterial surfaces, as well as thrombosis during injury.
1. M. Raghavachari, et al. Colloids Surf B (2000) 19:315.