The invention relates to a sorption agent having improved selectivity properties for removing protein-bound substances from a biological fluid, in particular blood or blood plasma of patients having severe disturbances of the liver function or liver failure and having kidney insufficiency, thee sorption agent having: (a) a porous, neutral, hydrophobic polymer and (b) a polypeptide layer adsorbed on the polymer, the neutral, hydrophobic polymer having a mean pore size of at least 15 nm. Furthermore, the invention relates to methods and uses in connection with such a sorption agent. The invention is used in particular in extracorporeal liver support.
