Removal of Protein-Bound Uremic Toxins by Mixed Matrix Membranes of Cellulose Acetate/Silica/MOF
João M Santos Dionísio1,2, Miguel P da Silva1,2, Ricardo F S Pereira3,4
1Center of Physics and Engineering of Advanced Materials (CeFEMA), Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, n. 1, 1049-001 Lisboa, Portugal.
Abstract:
Adsorption therapies in hemodialysis have emerged as an innovative approach for removing protein-bound uremic toxins (PBUTs). The present work focuses on the enhancement of the adsorption capacity of hemodialysis membranes through the incorporation of Metal-Organic Frameworks (MOFs). The removal capacity of PBUT p-cresyl sulfate by cellulose acetate (CA)/silica (SiO2)/MOF mixed matrix membranes was investigated with two types of MOFs, UiO-66 which synthesis and characterization has been previously reported, and UiO-66-NH2. The UiO-66-NH2 MOFs were synthesized and characterized by infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption equilibrium at -196 °C, and thermogravimetry analysis. Both mixed matrix membranes were synthesized by coupling the phase inversion technique with the sol-gel method and with casting solutions incorporating the MOF dispersions. The two membrane types of MOFs were characterized in terms of hydraulic permeability, molecular weight cut-off, and rejection coefficients to pCS and bovine serum albumin (BSA). The mixed matrix membranes CA/SiO2/UiO-66-NH2 exhibited lower permeability and molecular weight cut-off when compared to the CA/SiO2/UiO-66 ones. In permeation tests simulating a hemodialysis session with a feed solution of 100 ppm pCS and 35 g/L BSA, it is shown the improved performance of MOFs membranes as the rejection coefficients of free pCS is 0.2% for the CA22/SiO2/UiO-66 membrane with 1.5% of MOF and 2.6% for the CA22/SiO2/UiO-66-NH2 membrane with 2% of MOF. The capacity of these MOF membranes in removing pCS bound to BSA was addressed through the development of a new methodology to quantify the pCS free and bound to BSA. The CA22/SiO2/UiO-66 membrane with 1.5% of MOF has a removal capacity of 99.8% and the CA22/SiO2/UiO-66-NH2 membrane with 2% of MOF 95.9%. Based on these results, it is concluded that the mixed matrix membranes CA22/SiO2/UiO-66 and CA22/SiO2/UiO-66-NH2 are promising candidates for PBUTs removal in hemodialysis.
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