Abstract: Method for recovering a target protein from a feedstock comprising said target protein and at least one impurity compound selected from host cell proteins (HCP), DNA, RNA or other nucleic acid, the target protein being characterized by a hydrodynamic radius Rh1 and the impurity compound being characterized by a hydrodynamic radius Rh2, wherein Rh1>Rh2, comprising the following steps (i) to (iv) and optionally step (v): (i) providing a polymeric mesh comprising at least one crosslinked polymer containing positively charged amino groups, wherein the polymer has a pore size exclusion limit Rhi which can be set variably; (ii) adapting the variable pore size exclusion limit Rhi of the polymeric mesh such that Rh2<Rhi and Rh1>Rhi; (iii) contacting the polymeric mesh with the feedstock; (iv) separating the polymeric mesh containing the retained impurity compound from the feedstock containing the excluded target protein.