We have developed biocompatible ferrite (Fe3O4) nanoparticles whose surfaces are functionalized with biotin molecule. The resulting magnetic nanoparticles with an average diameter of 8 nm have a biotin-anchored morphology, which gives an exceptionally high affinity for the Cy3-labeled streptavidin. The spectroscopic and magnetic data results confirmed the presence of the interaction between biotin-anchored Fe3O4 particles and Cy3-labeled streptavidins. These biocompatible magnetic nanoparticles can be used as a basic protocol for various biological applications, particularly linking molecules together to create signal generation systems. (c) 2006 Elsevier B.V. All rights reserved.