Detection of nisin and fibrinogen adsorption on poly(ethylene oxide) coated polyurethane surfaces by time-of-flight secondary ion mass spectrometry (TOF-SIMS)

Stable, pendant polyethylene oxide (PEO) layers were formed on medical-grade Pellethane® and Tygon® polyurethane surfaces, by adsorption and gamma-irradiation of PEO–polybutadiene–PEO triblock surfactants. Coated and uncoated polyurethanes were challenged individually or sequentially with nisin (a small polypeptide with antimicrobial activity) and/or fibrinogen, and then analyzed with time-of-flight secondary ion mass spectrometry (TOF-SIMS). Data reduction by robust principal components analysis (PCA) allowed detection of outliers, and distinguished adsorbed nisin and fibrinogen. Fibrinogen-contacted surfaces, with or without nisin, were very similar on uncoated polymer surfaces, consistent with nearly complete displacement or coverage of previously-adsorbed nisin by fibrinogen. In contrast, nisin-loaded PEO layers remained essentially unchanged upon challenge with fibrinogen, suggesting that the adsorbed nisin is stabilized within the pendant PEO layer, while the peptide-loaded PEO layer retains its ability to repel large proteins. Coatings of PEO loaded with therapeutic polypeptides on medical polymers have the potential to be used to produce anti-fouling and biofunctional surfaces for implantable or blood-contacting devices.

Immobilized PEO–polybutadiene–PEO triblocks on medical polymers support the integration of small biofunctional peptides such as nisin, without compromising anti-fouling activity against large blood proteins.Figure optionsDownload high-quality image (36 K)Download as PowerPoint slideHighlights
► Nisin, a small antimicrobial polypeptide, becomes integrated in pendant PEO layers.
► Entrapment within pendant PEO layers enhances resistance of nisin to elution.
► Nisin-loaded PEO layers retain their ability to prevent adsorption of fibrinogen.
► Robust principal components analysis distinguishes proteins and detects outliers.