Synthesis and urea adsorption capacity of a strong, acidic hollow nanoparticle

To increase the quality of life of dialysis patients while maintaining economic efficiency, the concept of a wearable artificial kidney was proposed and designed approximately two decades ago. However, the primary challenge in the development of a wearable artificial kidney is the adequate removal of urea from dialysate due to the chemical inertness of urea under physiological conditions. Herein, a hollow polystyrene nanoparticle with sulfonic acid groups, named H-CPS-SO3H, was synthesized that could efficiently adsorb urea. H-CPS-SO3H was produced in three steps. First, a core-shell polystyrene nanoparticle with a linear core and cross-linked shell was prepared using modified emulsion polymerization. Second, the core-shell nanoparticles were treated with DMF to create hollow nanoparticles. Finally, the hollow nanoparticles were subjected to sulfuric acid treatment to produce H-CPS-SO3H, which was confirmed by both TEM and FTIR analysis. The urea adsorption capacity and kinetics of the as-synthesized H-CPS-SO3H were evaluated in a 30 mM urea aqueous solution. The results indicated that H-CPS-SO3H had a urea absorption capacity of up to 1 mmol/g, which was achieved after only two hours of adsorption at 37 °C. These findings demonstrated the high adsorption capacity and favorable adsorption kinetics of H-CPS-SO3H. Additionally, the adsorption capacity first increased and then slightly decreased with decreasing pH or increasing solution volume, while the adsorption capacity sharply decreased with increasing ionic strength. The results suggest that the prepared H-CPS-SO3H has promising application potential in the field of wearable artificial kidney devices. Achieving a wearable artificial kidney hinges on overcoming the critical challenge of developing efficient urea adsorption materials for dialysate regeneration. An acidic hollow polystyrene nanoparticle was synthesized by modified emulsion polymerization, DMF etching and sulfuric acid treatment sequentially. The nanoparticles had a urea absorption capacity of up to 1 mmol/g after two hours of adsorption in a 30 mM urea aqueous solution at 37 °C. Additionally, the adsorption capacity dramatically increased with increasing urea concentration, while sharply decreased with increasing ionic strength.