Magnetic Nanoparticles for Magnetic Hyperthermia and Controlled Drug Delivery

Abstract

Magnetic induced hyperthermia has been recently introduced as a new form of therapy to fight cancer. The preparation of superparamagnetic nanoparticles in the early 1980s, together with recent advances in the synthesis of magnetic inorganic nanomaterials of varying size, shape, composition, and magnetic performances, have set aside the old fashioned magnetic microimplants for magnetic hyperthermia and have made available new types of nano-heater probes that are less invasive and more appealing as drug delivery carriers. This chapter provides an introduction to magnetic induced hyperthermia, reviews the basic concepts of magnetic nanoparticles (MNPs) as heat mediators, and reports about recent advances in the preparation and exploitation of MNPs as heat mediators. Moreover, nanoparticles can also act as cargo systems for drug molecules. Their advantages as shuttle for a drug not only reside in their small size (which results in higher surface to volume ratio and thus a higher drug loading capacity together with the ability to escape the reticulum endothelial system) but also in their intrinsic magnetic properties. Nanoparticles can be only activated under exposure to an alternative magnetic field, therefore local heat is generated only under specific conditions. In this regard, the heat stimulus could be the trigger mechanism to release cargos with spatial and temporal release control. To this end, appropriate nanoparticle surface chemistry needs to be designed. We will provide examples of thermosensitive coatings developed so far by different groups, together with the latest concepts on the temperature gradient effects at the surface of MNPs. Finally, we will give examples of the recent exploitation of such local effects for drug or biological induced effects. Additionally, we will discuss the most advanced animal in vivo studies in which hyperthermia has been combined with drug release.