Static time‐of‐flight secondary ion mass spectrometry and x‐ray photoelectron spectroscopy characterization of adsorbed albumin and fibronectin films

Static time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), monochromatized x‐ray photoelectron spectroscopy (XPS) and 125 I radiolabeling have been used to characterize albumin films adsorbed onto titanium, gold, polytetrafluoroethylene and r.f. glow discharge‐deposited tetrafluoroethylene (TFE) substrates. A comparison between albumin and fibronectin films also was made. The intensities of characteristic amino acid mass fragments (immonium ions) detected in the static ToF‐SIMS experiments depended on the protein type, the substrate type and the adsorption conditions, demonstrating the sensitivity of static ToF‐SIMS for probing the structure of adsorbed protein films. Based on the results from albumin and fibronectin, static ToF‐SIMS can provide information about the identity of adsorbed proteins and their conformation, orientation, denaturation, etc. X‐ray photoelectron spectroscopy can distinguish pure protein films, but the higher molecular specificity of static ToF‐SIMS is more useful than XPS for examining complex protein films. The 125 I radiolabeling experiments and the XPS atomic percentage of nitrogen were used to quantify the amount of adsorbed protein.