TiO2 nanoparticles have attracted much attention in the surface modification of polymer membranes for antifouling purpose due to their excellent hydrophilicity. In this work, a polydopamine/poly-ethyleneimine (PDA/PEI) intermediate layer was fabricated on the polypropylene microfiltration membrane via a co-deposition method and then TiO2 nanoparticles (NPs) were modified on the membrane surfaces through a sol-gel process. TiO2-modified membranes with various Ti/C ratios were prepared and their surface structures and properties are compared with those of the nascent and PDA/PEI-deposited ones. Results indicate that the TiO2 NPs modification increases both the surface wettability and the water permeation flux of the membranes remarkably. TiO2 NPs also endow the membranes with promoted protein resistance properties. The relative flux reduction and flux recovery ratio are 31 +/- 3% and 82 +/- 5% for bovine serum albumin solution, while 26 +/- 4% and 86 +/- 3% for lysozyme solution. The TiO2 NPs are also stable on the membrane surfaces under a wide range of pH value. (C) 2015 Elsevier B.V. All rights reserved.