This paper reports a novel method to synthesize magnetic, stimuli-sensitive latex nanoparticles made with magnetite/poly(N-isopropylacrylamide-co-acrylic acid) (Fe3O4/P(NIPAAm-co-AAc)). To form a stabilized suspended core, iron oxide (Fe3O4) was functionalized with AAc such that further polymerization with NIPAAm and AAc monomers could occur. The P(NIPAAm-co-AAc) shell layer exhibited thermosensitive properties. The inclusion of Fe3O4 into the latex nanoparticles was confirmed using transmission electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction spectroscopy, thermogravimetric analyzer (TGA), and superconducting quantum interference device magnetometer. The NIP-(AAc2.6-Fe) latex nanoparticles contained 2.25% Fe3O4 (by weight), as determined by TGA analysis. The particle diameters measured approximately 160-240 nm with a lower critical solution temperature of 35 degrees C. These novel magnetic stimuli-responsive latex nanoparticles have potential applications in numerous fields, such as catalyst supports, protein immobilization, cancer therapy, target drug delivery systems, and other biomedical applications. (C) 2012 Elsevier Ltd. All rights reserved.