Adsorptive membranes of cellulose acetate CA/SiO2/UiO-66(Zr) for the removal of protein bound uremic toxins

Abstract

One of the strong limitations of hemodialysis is the fact that protein bound uremic toxins (PBUTs), such as p-Cresyl Sulfate (pCS), are not filtered out, remaining in the patient’s bloodstream, leading to a worsening of the chronic kidney disease (CKD).In the present work, the MOF (Metal Organic Framework) UiO-66(Zr) is incorporated into CA/SiO₂ membranes in order to increase their capacity to remove uremic toxins, that preferentially bind to plasma proteins, such as pCS. The casting solutions for membrane synthesis by phase inversion combined with sol–gel method are prepared with 1%, 1.5%, 2% and 2.5% of MOF to yield CA22/SiO₂ membranes with these contents.The four membranes containing increasing MOF contents showed an increase of hydraulic permeability ranging from 14.38 to 33.82 kg/h/m²/bar and of molecular weight cut-off ranging from 3.5 to 14.7 kDa.Adsorption isotherms were constructed at 37 °C for pCS on UiO-66(Zr) and on Bovine Serum Albumin (BSA) and for all the four membranes incorporating MOF. It was concluded that the membrane adsorption, per MOF mass, decreases with increasing MOF content. The Langmuir and Freundlich parameters were calculated for each case. Finally, a last adsorption isotherm was carried out on pCS in the presence of both UiO-66(Zr) and BSA, where with 5 mg/mL of UiO-66(Zr) it was possible to reduce the bounding of the toxin to the protein by around 50 %.