Quantification of fibrinogen adsorption onto 316L stainless steel

Adsorption of the plasma protein fibrinogen (Fb) onto 316L stainless steel (316L SS) was observed and quantified using both in situ and ex situ atomic force microscopy techniques. Industry standard mechanical and electrochemical polishing techniques were used to prepare bulk alloy 316L SS samples, rendering the surfaces flat enough to directly observe and measure Fb adsorption. The data were analyzed kinetically using a Langmuir model. Largely irreversible adsorption was found on the 316L SS surface with an adsorption rate constant (k_O) of 1.9 × 10^-4 mL μg^-1 s ^-1 using the ex situ method and 1.7 × 10^-4 mL μg^-1 s^-1 using the in situ method. Additionally, protein conformation and assembly orientation on these surfaces were documented, where the adsorption pattern appeared random. Complete area coverage was never obtained. That is, after adsorption for over 5 time constants (5τ), voids in the structure were always observed.