XPS and FT-IR spectroscopy study of albumin adsorption on the surface of a p-conjugated polymer film

The interaction between thin films of polyphenylacetylene (PPA) and bovine serum albumin (BSA) dissolved in phosphate buffer solution (PBS) was studied by x-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FT-IR) performed in reflectance mode. PPA is a semiconducting pi-conjugated polymer consisting of a polyene backbone with phenyl pending groups, that has been used in the preparation of humidity sensors; therefore, we have tried to pre-test PPA films for possible applications as biosensors. Thin films of PPA were incubated in buffered albumin solution (BSA/PBS) for increasing exposure times (24-96 hours). BSA adsorption on the PPA film surface takes place as demonstrated by the appearance of the N 1s signal and by the modifications in the C 1s core-level signal in the XPS spectra of the samples treated with albumin solution; time-dependent adsorption is also observed. Phosphate salts are co-adsorbed on the PPA surface upon treatment with BSA/PBS solution. Albumin adsorption on the PPA surface was confirmed by FT-IR measurements