The use of nitrilotriacetic acid end-functionalized polystyrenes (NTA-PS) as a multifunctional nanocarrier for the aqueous dispersion of CdSe, ?-Fe2O3 and gold nanoparticles (NPs) is described. When the amphiphilic end- functionalized polystyrenes and NPs are dissolved together in tetrahydrofuran, the addition of water causes the spontaneous formation of micellar aggregates, resulting in the successful encapsulation and aqueous dispersion of NPs. Transmission electron microscopy (TEM), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy, and vibrating sample magnetometer (VSM) are used to characterize the structure and properties of the NPs-containing micellar aggregates (nanocarrier). After complexation of Ni2+ with NTA on the surface of the nanocarrier containing ?-Fe2O3, specific binding between Ni-NTA complex and histidine-tagged (His-tagged) proteins enables selective separation of His-tagged proteins using a magnet.