Silastic adsorbed

Chlormethiazole Edisylate Chlormethiazole edisylate may penetrate or be adsorbed onto plastics and may soften plastic sets of intravenous infusions. Adverse reactions such as thrombophlebitis, fever, and headache were reported in children receiving infusions of this drug, presumably due to reaction of components of infusions sets. For intravenous infusions, the use of Teflon intravenous cannulas or motor-driven glass syringes may be preferred over plastic or glass sets containing silastic cannulae.153154... 

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 thrombotic response to uncoated PVC and to uncoated Silastic would be expected to be identical if thrombosis is surface nonspecific or if the surfaces initially adsorb the same proportion of the various plasma proteins that influence thrombosis. Comparisons of the responses of the uncoated surfaces (Figure 2 with 5 and 3 with 6) reveal that both the fibrin(ogen) and platelet deposition profiles on uncoated Silastic were significantly different than those on PVC. Fibrin(ogen) deposition proceeded at a slower rate on uncoated Silastic than on uncoated PVC, and peaked after 30 min of blood... 

Figure 5. Transient fibrin deposition ( sem) on adsorbed protein substrates. Key A (SIL), uncoated Silastic (N = 5) (y-GLB), y-globulin on Silastic (N = 3) (FN), fibronectin on Silastic (N = 6) and A (a2M), a2-macroglobulin on Silastic (N =4).

Figure 7 shows that Silastic initially (2 min of blood contact) adsorbed albumin, y-globulin, fibrinogen, and fibronectin in the relative ratios of 100 52 33 3, where the surface concentration of serum albumin was 300... 

The fibrin(ogen) and platelet response to y-globulin-coated Silastic was similar to that on y-globulin-coated PVC. On both surfaces the relative rate of deposition of fibrin(ogen) initially (Table I) was much less than that of the platelets. On Silastic, the preadsorbed y-globulin was 11 times more concentrated than the amount that would be adsorbed onto the uncoated surface. Not much embolization occurred during an experimental blood exposure time of 120 min. 

Figure 9 shows HSA adsorption isotherms on different hydrophobic polymer surfaces studied by Winterton et al. [1]. An radiolabeling technique was used to measure the adsorbed mass of HSA. The isotherm experiments were carried out at pH 7.4, with protein dissolved in a PBS buffer. The polymers used in HSA adsorption were polystyrene (PS), poly(vinyl chloride) (PVC), and silastic (Silas). Tables 12 and 13 show the relevant thermodynamic and regression data for HSA adsorption isotherms on these polymers. 

Figure 20 summarizes the result of BSA adsorption to the polymer films. We used BSA as model for protein because albumin is the protein that is most prominently present in human blood serum. The BSA adsorption onto regenerated cellulose, which had a highly hydrophilic surface, was extremely low. These data gave the same result reported in the previous study [70]. On the other hand, the adsorbed amounts of BSA onto aramid and nylon were high (0.5-0.6 p,g/cm ). For the PASs, the amount of BSA was almost half the amounts of those with aramid and nylon, but similar to that for SILASTIC 500-1, and more than that of the regenerated cellulose. There was no difference in the adsorbed amounts onto the three samples of PASs. In the previous work, PDMS blocks were condensed at the outermost surface of PAS [10]. The phenomenon of protein adsorption onto PAS seems to be due to the low surface free-energy of the PAS surface [71-73] caused by the condensation of PDMS blocks on the outermost surface of PAS. Therefore, the BSA was bound onto PAS surface as well as the surface of the silicone rubber [74,75]. 

Since Silastic Rubber adsorbs about 70% albumin on its surface and yet is mildly thrombogenic, one would estimate that the albumin content on the surface must be greater than 70% of the total protein adsorbed if the polymer is to be nonthrombogenic. 

---