Sodium hydroxide solution

Polyether sulfone (PES) flat sheet membranes were prepared by non-solvent induced phase separation (NIPS). Chemicals were purchased from Sigma Aldrich (St. Louis, MO, USA): aluminum oxide (Brockmann activity I, Fluka), 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AIBA), lauryldimethylammonia acetate, latex beads (~1 µm, amine-modified, fluorescent red, L2778), latex beads (~1 µm, carboxylate-modified, fluorescent yellow-green, L4655), lysine, 1-methyl-2-pyrrolidone (NMP), potassium persulfate (KPS), styrene. The 2-Aminoethyl methacrylate hydrochloride (AEMA, Acros Organics), polyethylene glycol (PEG, 400 g mol⁻¹, Acros Organics), and sodium bicarbonate were purchased from Thermo Fisher Scientific (Geel, Belgium). Other purchased chemicals: glutaraldehyde (GA, Merck, Darmstadt, Germany), n-hexane (Merck, Darmstadt, Germany), hydrochloric acid solution (0.1 M, VWR, Radnor, DE, USA), polyether sulfone (PES, Ultrason E2010, BASF, Ludwigshafen, Germany), sodium carbonate (anhydrate, VWR, Radnor, DE, USA), sodium hydroxide solution (0.1 M, VWR, Radnor, DE, USA).
All chemicals were used as received. Ultrapure water was taken from a MilliQ-System (Merck Millipore, Billerica, MA, USA). The dialysis membranes used for the bead purification were obtained from Carl Roth (cellulose acetate, Nadir, molecular weight cut-off (MWCO): 10–20 kDa, Wiesbaden, Germany).

Bis-Tris propane (BTP, ≥99.0%), 2-amino-2-methyl-1,3-propanediol (AMPD, ≥99.0%), N-(1,1-dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid (AMPSO, ≥ 99.0%), 2-(cyclohexylamino)ethanesulfonic acid (CHES, BioUltra, ≥99.5%), 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid (CAPSO, ≥99% anhydrous basis), magnesium chloride hexahydrate (BioXtra, ≥99.0%), hydrochloric acid solution (1 N), sodium chloride (BioUltra, for molecular biology, ≥99.5%), potassium chloride (BioUltra, for molecular biology, ≥99.5%), tetramethylammonium chloride (TMAC, LiChropur, ≥99.0%) were purchased from Sigma-Aldrich (Buchs, Switzerland). Sodium hydroxide solution (1 N) was obtained from VWR Chemicals. Phosphate-buffered saline (PBS) and poloxamer 188 were obtained from Roche Diagnostics GmbH (Penzberg, Germany). Water was provided by a Milli-Q purification system from Millipore (Bedford, MA, USA).

Poly(vinylidene fluoride) membranes (hydrophobic, pore size 0.45 μm, thickness 125 μm) were purchased from Carl Roth GmbH & Co. (Karlsruhe, Germany). Tetraethylenepentamine, ethanol, bovine serum albumin (fraction V, pH 5) (isoelectric point (IEP) = 4.7, molecular mass = 67,200 Da, acidic protein), myoglobin from equine skeletal muscle (95%–100%, essentially salt-free, lyophilized powder, IEP = 7.0, 17,800 Da, neutral protein), lysozyme from chicken egg white (lyophilized powder, protein 90%, 40,000 units/mg of protein, IEP = 11.1, 14,600 Da, basic protein), glycidol, pyridine (water-free), succinic anhydride were purchased from Sigma-Aldrich (Steinheim, Germany). Other purchased chemicals: 2-aminoethyl methacrylate hydrochloride (Acros Organics, Waltham, MA, USA), glutaraldehyde (Merck, Kenilworth, NJ, USA), hydrochloric acid solution (0.1 M, VWR), sodium hydroxide solution (0.1 M, VWR), sodium carbonate (anhydrate, VWR), sodium bicarbonate (Waltham, MA, USA). Bicinchoninic acid (BCA) protein assay reagent A + B was provided by Pierce (Rockford, IL, USA). Phosphate-buffered saline (PBS; 50 mM) was used at pH 7. If not otherwise stated Millipore^® grade water was used. All chemicals were of analytical grade and used without further purification.