Nanostructured polyurethane biomaterials and protein adsorption and platelet adhesion on surfaces

PHYS 499

Li-Chong Xu, lxx5@psu.edu1, Pranav Soman2, Jadwiga Weksler3, Ajay Padsalgikar3, James Runt, runt@matse.psu.edu4, and Christopher A. Siedlecki, csiedlecki@psu.edu5. (1) Department of Surgery and Biomedical Engineering Institute, The Pennsylvania State University College of Medicine, Hershey, PA 17033, (2) Department of Bioengineering, The Pennsylvania State University, Hershey, PA 17033, (3) 2AorTech Biomaterials, Scoresby, VIC, Australia, (4) Department of Materials Science and Engineering, Penn State University, 101 Steidle Building, University Park, PA 16802, (5) Departments of Bioengineering and Surgery, Pennsylvania State University, College of Medicine, 500 University Dr, Hershey, PA 17033
Understanding the surface properties influencing thrombus formation is a key to the development and application of new biomaterials for use in long term blood-contacting medical devices. In this study we utilized a series of polyurethane (PU) biomaterials with different soft segments chemistries - polycarbonate (PC), polytetramethylenoxide (PTMO), and polydimethylsiloxane (PDMS), that have a variety of heterogeneous surface chemistries. AFM was used to characterize the polymer surface microphase separation structure of PUs and to identify adsorbed fibrinogen on the surfaces so that relationships between biomaterial surface chemistry, fibrinogen adsorption, and platelet adhesion could be addressed. AFM phase images show that PDMS-PUs undergo strong phase separation and suggest three phases (soft, intermediate and hard domains) present in structure, while PC-PU and PTMO-PU appear to have two-phase structures. The sizes of the hard domains in these materials under ambient and aqueous environments were quantified by the phase image analysis. Results show that the size of hard domains increases upon hydration and the surface becomes hard-segment enriched. Platelet adhesion was found to increase with hard segment content from the range of 35% to 52% hard segment. Fewer platelets were observed on PC-PU and PTMO-PU. The amount of fibrinogen adsorbed on the surface was detected through antibody recognition measurements using AFM probes modified with a polyclonal anti-fibrinogen antibody. Results show that fibrinogen adsorption was roughly correlated to platelet adhesion on the PDMS-PUs, although more fibrinogen was measured on the PC-PU and PTMO-PU surfaces despite the fact that fewer platelets were observed. The activity of fibrinogen was further identified using a monoclonal anti-fibrinogen antibody-modified AFM probe. Results showed that platelet adhesion is not necessarily determined by the amount of fibrinogen, but seems more likely related to the number of fibrinogen with availability of the platelet binding site in the fibrinogen gamma chain dodecapeptide.
 

PHYS Poster Session - Nanostructured Materials and Nanophotonics
7:30 PM-10:00 PM, Wednesday, April 9, 2008 Morial Convention Center -- Hall A, Poster

Sci-Mix
8:00 PM-10:00 PM, Monday, April 7, 2008 Morial Convention Center -- Hall A, Sci-Mix

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008