Effect of End-Tethered Methoxy-PEO Chain Density on Uremic Toxin Adsorption

In 2023, around 850 million people globally were affected by chronic kidney disease, which leads to the retention of uremic toxins and excess fluid in the blood. This study examines the adsorption of these toxins to poly(ethylene oxide) (PEO) films, known for their low-fouling properties. The gold surfaces were treated with 5 mM end-thiolated methoxy-terminated PEO (<i>m</i>-PEO) and analyzed using dynamic contact angle measurements, X-ray photoelectron spectroscopy, and spectroscopic ellipsometry to confirm the PEO film's presence and determine chain density. The adsorption of 25 different uremic toxins to <i>m</i>-PEO films was evaluated by using liquid chromatography-mass spectrometry (LC/MS), focusing on their binding affinity and adsorption dynamics. Results showed the effective modification of surfaces with <i>m</i>-PEO, with a notable change in contact angles and chain density (∼0.5 and 0.8 chains/nm²). Interestingly, pyruvic acid showed significant adsorption, whereas other toxins, such as hippuric acid, creatinine, and xanthosine had minimal interactions with the film. This indicates that the adsorption of these toxins is not primarily concentration driven and is rather dependent on the chemical structure of each toxin. These findings provide important insights for designing low-fouling coatings for biomedical devices.