Surface modification of polyurethane biomaterials by ammonia plasma: bacterial adhesion and cellular response

Abstract

Polyurethanes (PUs) are versatile polymers widely used in biomedical applications due to their tunable properties. However, PU-based medical devices are susceptible to bacterial contamination, necessitating surface modifications to improve biocompatibility and reduce colonization. This study introduced amine groups (–NH₂) onto PU surfaces using low-temperature ammonia plasma and evaluated effects on bacterial adhesion and biocompatibility. X-ray photoelectron spectroscopy (XPS), contact angle measurements, atomic force microscopy (AFM), fluorescence microscopy, and biocompatibility assays were employed. Ammonia plasma effectively introduced amine groups, confirmed by XPS. The contact angle decreased markedly (from 101.5° to 36.3°), accompanied by a pronounced increase in surface free energy (from 27.3 to 64.6 mJ/m²), indicating enhanced hydrophilicity, while AFM analysis revealed no significant changes in surface roughness (RMS). Bacterial adhesion increased for P. aeruginosa DSM 22644, S. aureus DSM 4910, and S. epidermidis DSM 28319, but was unaffected for E. coli DSM 18039. Biocompatibility tests with A549 cells showed improved adhesion, morphology, and cytoskeletal organization, with elevated focal adhesion kinase (FAK) expression. Ammonia plasma thus enhances PU biocompatibility while influencing bacterial adhesion.