In situ synchrotron imaging to investigate the influence of protein-bound uremic toxins (PBUT) on protein adsorption on hemodialysis membranes

The removal of protein-bound uremic toxins (PBUTs) during hemodialysis (HD) remains a significant challenge in the management of patients with end-stage renal disease (ESRD). PBUTs, such as p-cresyl sulfate (p-CS), indoxyl sulfate (IS), and indole-3-acetic acid (IAA), bind strongly to human serum albumin (Alb), impairing their efficient clearance and contributing to adverse health outcomes including cardiovascular disease, oxidative stress, and inflammation. This study leverages in situ synchrotron radiation micro-computed tomography (SR-μCT) to investigate the influence of PBUTs on protein adsorption across different depth layers of polyethersulfone (PES) hemodialysis membranes. By analyzing the adsorption behavior of Alb, both individually and in mixtures with fibrinogen and transferrin, in the presence and absence of PBUTs, we provide depth-resolved insight into PBUT-associated protein adsorption within the membrane structure. Our findings reveal that p-CS is associated with enhanced Alb adsorption on PES membranes, particularly under mildly acidic conditions, while IS induces heterogeneous adsorption patterns suggestive of complex interactions. In contrast, IAA exhibits a comparatively modest effect, with minimal enhancement of protein adsorption. These results reveal distinct depth-resolved attenuation profiles associated with different PBUT conditions, suggesting differences in protein accumulation behavior within PES membranes. The findings provide a foundation for future studies integrating direct PBUT transport measurements, membrane fouling analyses, and physicochemical characterization to further elucidate PBUT-associated protein–membrane interactions.