Magnetic nanoparticles (MNPs) were modified by polyaspartate (PAA) and poly(ethyleneimine) (PEI) via Layer-by-Layer self-assembly. Two steps were involved in: the first was to coat MNPs by PAA at pH 6; the second was to coat the former by PEI. The successful surface modification of MNPs was confirmed using X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA) and fourier transform infrared (FTIR) measurements. The modified MNPs interact strongly with negative fibrinogen and weakly with neutral gamma-globin and positive lysozyme. (C) 2011 Elsevier B.V. All rights reserved.