For efficiently sieving active molecules to concentrate/purify antibiotics, the pores of novel hydrophilic polyethylene glycol (PEG) based nanofiltration (NF) membrane should be finely tailored. Herein, an effective coating layer is successfully built on the PEG based NE membrane through self-polymerization of mussel-inspired dopamine (DA) which is confirmed by various physicochemical characterizations. Interestingly, with smaller pores, the hydrophilic PEG based membranes after coating with mussel-inspired polydopamine can significantly increase the rejections to salts and other active molecules with only little sacrifice of dual resistance to fouling and chlorine. Importantly, the best comprehensive antibiotics separation performance of NE membrane can be achieved by mussel-inspired dopamine modification around 6 h. Such an advanced membrane shows the highly stable tobramycin solution flux over 46 L m(-2) h(-1) alongside tobramycin (TUB), clindamycin phosphate (CP) and cephalexin (CA) rejections up to 99%, 94% and 93% with 50 ppm feed concentration under 8.0 bar, respectively. Interestingly, when the feed concentration increases up to 800 ppm, the membrane still exhibits the high rejections to all of antibiotics up to 90%. Therefore, coating with mussel-inspired dopamine is a highly effective way to tailor the pores of hydrophilic PEG based NE membranes toward the excellent separation performance for expanding membrane applications in separating negative and amphiprotic charged antibiotics. (C) 2015 Elsevier B.V. All rights reserved.