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.