Cross-Linker-Based Design of Selective Macroporous Polymer Resins for Uremic Toxin Removal

Uremic toxins pose a significant threat to the health and longevity of kidney dialysis patients, and their broad range of molecular weights and chemical properties presents a challenge to adsorption-based removal strategies. Developing efficient adsorbent materials capable of selective toxin capture is crucial for improving the dialysis outcomes. In this work, macroporous polymer resins (MPRs) with different chemical functionality were synthesized via bulk polymerization to investigate how uremic toxin adsorption is impacted by different molecular structures in a cross-linked network structure. Five multifunctional monomers (cross-linkers) with varying hydrophobicity (log P -0.36 to 3.57) were employed: ethylene glycol dimethacrylate (EGDMA), trimethylolpropane trimethacrylate (TRIM), poly(ethylene glycol) diacrylate (PEGDA-575), methylene bis(acrylamide) (MBAam), and divinylbenzene (DVB). Successful network formation in the resins was confirmed by FTIR and XRD analyses. The MPRs exhibited distinct morphologies and surface areas ranging from 183 to 975 m²/g, as characterized by SEM and BET porosimetry. Uremic toxin adsorption studies were conducted in peritoneal dialysis fluid and aqueous solutions containing β₂-microglobulin (B2M, 11.8 kDa) and urea (60 Da) respectively. The EGDMA-based MPR exhibited a remarkable B2M adsorption capacity (2837 μg/g), achieving removal efficiency 20-fold higher than activated carbon despite lower surface area (406 vs 756 m²/g). It was proposed that the synergistic interplay between amphiphilic chemistry (log P = 1.74), optimal pore architecture featuring hierarchical morphology with interconnected macro- and mesopores (average diameter 3.58 nm), collectively enhanced B2M capture. Conversely, urea adsorption was negligible across all MPR networks, with activated carbon outperforming synthetic materials. These contrasting profiles demonstrated the importance of cross-linker selection on adsorption selectivity, thus providing the platform for tuning and designing the right molecular chemistry to enable toxin-selective adsorbents for dialysis applications.