Adsorption of bovine serum albumin and fibrinogen on hydrophilicity-controllable surfaces of polypyrrole doped with dodecyl benzene sulfonate—A combined piezoelectric quartz crystal impedance and electrochemical impedance study

Combined measurements of piezoelectric quartz crystal impedance (PQCI) and electrochemical impedance (EI) were utilized to monitor in situ adsorption of two proteins (bovine serum albumin and fibrinogen) onto the hydrophilicity-controllable surfaces of polypyrrole (PPY) doped with dodecyl benzene sulfonate (DBS). Three of these polymer films, PPY/DBS-I, PPY/DBS-II and PPY/DBS-III, were obtained by galvanostatic electropolymerization of pyrrole in aqueous solutions containing 0.6, 1.2 and 2.0 mmol L⁻¹ sodium dodecyl benzene sulfonate (SDBS), respectively. The PPY/DBS-II obtained from electropolymerization of pyrrole in the presence of 1.2 mmol L⁻¹ SDBS (the critical micelle concentration of SDBS in aqueous solution, CMC) exhibited the greatest hydrophobicity, as suggested by contact angle measurement. And the saturation-adsorption amounts for both proteins were found to be greatest on the surface. The kinetics and adsorption mechanisms of both proteins adsorbed on these three surfaces were discussed. Langmuir and Freundlich models were used for explaining the adsorption behavior of proteins, giving that Langmuir model is better for bovine serum albumin (BSA) and both model are not so available for fibrinogen.