The Orientation of Human Fibrinogen at Biomedically Relevant Polydimethylsiloxane–Water Interfaces

The adsorption of fibrinogen on biomaterial surfaces, particularly polydimethylsiloxane (PDMS), plays a key role in foreign body reactions and has recently been shown to be one of the main factors driving catheter-associated urinary tract infections (CAUTIs). Yet, despite detailed studies on the fibrinogen's solution and crystal structures, its behavior at material interfaces is less understood. Using sum frequency generation (SFG) spectroscopy and structural modeling, we determined the binding pose and conformation of human fibrinogen at the PDMS-buffer interface. Fibrinogen adopts an upright orientation on PDMS with minimal bending. Comparisons with spectra recorded at the air-water interface and literature data on polystyrene reveal significant differences in orientation: fibrinogen binds flat and bent at these model hydrophobic interfaces, while upright conformations are observed on liquid PDMS. These findings demonstrate specific interaction beyond simple hydrophobic attraction at the PDMS interface and hint at the critical role of surface chemistry in dictating fibrinogen's interfacial structure and its implications for biomaterial design aimed at reducing foreign body reactions and CAUTIs.