This study has developed a novel route for the synthesis of the thermoresponsive core-shell nanoparticles that consist of the magnetite core and the poly(N-isopropylacrylamide) (poly(NIPAAm) shell in aqueous medium. Magnetic nanoparticles (MNPs) were coated first with oleic acid (OA) and then vinyl carboxylic acid-beta-cyclodextrin (MAH-beta-CD). The OA-MNPs and the MAH-beta-CD-MNPs showed mono-dispersion in n-hexane and aqueous medium, respectively. NIPAAms were successfully polymerized from the vinyl double bonds of the MAH-beta-CD MNPs and cross-linked with N, N-methylenebisacrylamide (MBA) to make the stable thermoresponsive core-shell morphology with the MNP core and the poly (NIPAAm) shell (poly(NIPAAm)-MNP). The aqueous solutions dispersed with poly(NIPAAm)-MNPs showed magnetic heating due to a superparamagnetic property, and the poly(NIPAAm) shell shrank above its LCST temperature. The combination of these properties are potentially important in the targeted delivery of therapeutic agents in vivo, hyperthermic treatment of tumors, magnetic resonance imaging (MRI) as a contrasting agents, tissue repair, immunoassay, cell separation, biomagnetic separation of biomolecules, etc. (C) 2010 Elsevier Ltd. All rights reserved.