Polyacrylamide-silastic

Thrombotic Events on Grafted Polyacrylamide—Silastic Surfaces as Studied in a Baboon... 

Laser Light Scattering Detection of Microemboli. To elucidate the mechanism of platelet destruction by grafted polyacrylamide-Silastic surfaces, an optical scattering technique was developed (20) to observe and quantitate the sizes and size distributions of microaggregates in blood produced within the AV baboon shunt. Presumably, any such flowing microaggregates represent platelet microemboli. 

Figure 4. Graft level as a function of length along the shunt for polyacrylamide-Silastic shunts prepared using the flow-grafting apparatus described in Ref 14.

Figure 7a. ESC A C Is spectrum of the luminal surface of polyacrylamide-Silastic tubing in the dehydrated state.

Protein Adsorption. Since protein adsorption is the earliest event in the thrombotic response of the blood to polymers, the types of proteins adsorbed from plasma to polyacrylamide-Silastic and Silastic tubes were examined. As described in the Experimental section, plasma was recirculated through the tubes for 2 h at 37°C and rinsed away with buffer. The proteins adsorbed to the polymers were eluted with SDS, separated by SDS-polyacrylamide slab gel electrophoresis, and silver-stained using a new extremely sensitive method (19). Figure 10 shows the results of these assays. 

The eluate from polyacrylamide-Silastic had six distinct proteins in it (Gel 2 in Figure 10). The most prominent bands had molecular weights of... 

Figure 8. ESCA Cl s spectra for polyacrylamide-Silastic (21). Key a, 160 K (hyarated) ana b, 303 K (dehydrated).

The eluate from Silastic (Gel 1 in Figure 10) had only three visible bands, each of which was much less intense than the corresponding bands in the eluate from polyacrylamide-Silastic. Two of the bands from Silastic occurred at 131,000 and 58,000 Daltons, and had approximately the same stain intensity. A third band of even lower intensity occurred at 95,000 Daltons. 

Table II shows the effect on platelet consumption of increasing lengths of the polyacrylamide-Silastic tubing. The acrylamide surface is much more destructive to platelets than is the Silastic surface. Table II also shows that platelet consumption increases linearly with shunt area for both the polyacrylamide-Silastic shunts.

Laser Light Scattering Detection of Microemboli. The optical scattering technique was used to assess in vivo the thromboembolic propensity of polyacrylamide-Silastic and Silastic shunts of varying lengths. In four baboons, control measurements of the number and size distribution of throm-boemboli produced by the 35-cm proximal section of the chronically... 

Figure 11. Platelet consumption vs. graft level of polyacrylamide-Silastic shunts (9). (Numbers in parentheses refer to the number of shunts tested for each value reported.)...

The radiation grafting technique used to prepare the polyacrylamide-Silastic grafts is a practical method for immobilizing the mechanically weak... 

Figure 12. Rates of production of thromboemboli volume ( 3Is) and equivalent platelet consumption by embolization (platelets/day) vs. surface area for two biomaterials Silastic (bottom) and polyacrylamide-Silastic (top). The equivalent steady-state platelet consumption is (3.0 0.2) x 108 (platelets day-cm2) for polyacrylamide-Silastic and (0.8 0.1) X 108 (platelets day-cm2) for Silastic.

Because fibrinogen remains at the gel top in the electrophoresis system used here, we cannot assess its importance because staining artifacts frequently occur at the gel top. However, adsorption of 125I-fibrinogen to polyacrylamide-Silastic shunt surfaces from baboon blood in vivo is much greater than adsorption to Silastic shunt surfaces (46). 

Title Thrombotic Events on Grafted Polyacrylamide-Silastic Surfaces as... 

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