grantor:
University of TorontoPlatelet compatibility of amidine groups on poly(acrylonitrile-co-vinyl chloride) (PAN-VC) was studied using PAN-VC cast into thin films. The surface nitrile groups of the PAN-VC films were chemical modified into amidine groups through a two-step process analogous to the Pinner's methods. The presence of amidine groups was shown in various surface characterization tests, including x-ray photoelectron spectroscopy (XPS), chemical derivatization with pentafluorobenzaldehyde (PFB), infrared spectroscopy (IR) and static secondary ion mass spectrometry (SIMS). A higher nitrogen content was detected on the amidine-surface modified (ASM) samples in low-resolution XPS spectra compared to the solvent-treated control and unmodified PAN-VC. After reacting with PFB, lower nitrogen and higher fluorine contents were found, indicating the presence of Schiff bases formed with primary and secondary amines and hence the presence of amidine, on ASM PAN-VC surface. Further supporting evidences was also observed in IR and SIMS analysis. However, the yield of the surface-modification was low, around 8% of the total surface nitrile group available on the surface. Flat surface platelet adhesion tests showed that platelet adhesion was ~40% lower on the ASM PAN-VC compared to the control and unmodified surfaces. Flow cytometric analysis showed that the amidine surface modification was able to slightly reduced platelet activation in the bulk on PAN-VC surface. The significantly lower platelet adhesion and the small but statistically insignificant decrease in platelet adhesion suggests that there may be more than one platelet activating mechanism and that the amidine-surface modification could inhibit some, but not all of the activating pathways. Nevertheless, amidine-surface modification was shown to be able to improve the platelet compatibility of the PAN-VC surface. This study showed that the amidine groups on a polymer surface were very likely to function in a similar way to ones on soluble agonists in the bulk fluid, and could reduce thrombogenicity in material-blood contact.M.A.Sc
