The adsorption of thrombin to polypropylene tubes: the effect of polyethylene glycol and bovine serum albumin.

The adsorption of 125I-thrombin to polypropylene tubes has been studied with thrombin dissolved in tris-buffered saline (TBS), TBS with 0.66% polyethylene glycol (PEG), and TBS with 0.01% or 0.20% bovine serum albumin (BSA). Adsorption stabilized over time from all three solutions, increased with increasing concentrations of unadsorbed thrombin, and was reversible by repetitive washing. At equilibrium, more thrombin adsorbed from TBS-PEG than from TBS. The difference was attributable to an increased amount of thrombin deposited by evaporation during aspiration of the polypropylene tubes. Adsorption equilibrium and capacity were otherwise relatively unaffected by the presence of PEG. However, PEG was effective in retarding thrombin adsorption by markedly reducing the adsorption rate. Reduction of adsorption in the presence of BSA, on the other hand, was explained by competitive inhibition. Pretreatment of the tubes with PEG or BSA was also shown to be effective in reducing thrombin adsorption from TBS.