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 T2 relaxation agent.