Magnetic and MR relaxation properties of avidin-biotin conjugated superparamagnetic nanoparticles

Recently, much attention has been given to the development of novel biomedical imaging applications of bio-functionalized nanoparticles which possess optical, magnetic, and opto-magnetic properties for molecular and cellular events. For bioconjugation the avidin-biotin system is often introduced as a linker between nanoparticles and biological markers. In case of magnetic resonance imaging (MRI), it is important to investigate the magnetic property of avidin-biotin linker system in addition to superparamagnetic nanoparticle itself. In this study, we investigate the alteration of magnetic properties of magnetic nanoparticle by avidin-biotin system and the change of the MR relaxation property by synthesizing and characterizing a polycaprolactone coated iron oxide nanoparticles (PCLNP), avidin conjugated PCLNP (A-PCLNP) and avidin-biotin conjugated PCLNP (A-B-PCLNP). Our results demonstrated that diamagnetic property of the avidin-biotin system reduced the total magnetization of avidin-biotin conjugated superparamagnetic nanoparticle and thus reduced the efficiency as an MR T-2 relaxation agent. (C) 2007 Elsevier B.V. All rights reserved.