The present investigation deals with studies on novel magnetic resonance signal-enhancing coating materials. The polyaminocarboxylate complexes of Gd3+ as side chains were prepared by the conjugation of N-(2-hydroxvethyl)ethylenediaminetriacetic acid (HEDTA) with poly(styrene-maleic acid) copolymer (SMA). The complexation of the Gd3+ ion to the conjugates was carried out by adding GdCl3 to the solution of the polymer ligands. The resulting Gd3+-containing polymer complexes were characterized by GPC, FTIR, NMR, and inductively coupled plasma-Auger electron spectroscopy, which confirmed that HEDTA was covalently attached to SMA and Gd3+-containing polymer complexes were formed. The PP catheters were coated with the Gd3+-containing polymer complexes and characterized by XPS. The result confirms that the Gd3+ complexes were coated on the surface of PP catheters. In the relaxation test, the relaxation rates of the water proton in the vicinity of the coated PP catheter surface increase significantly, suggesting that Gd3+-containing polymer complex coating materials show great MR enhancement of water proton, and potentialities in making catheters used for endovascular interventions or therapy, visible by MRI. The influence of protein on the relaxation rates of coated PP catheter shows that the protein adsorption on the catheter surface influences the enhancement of the MR signal for the coating materials of Gd3+-containing polymer complex.