**Multifunctional Magnetic Hybrid Nanoparticles as a Nanomedical Platform for Cancer-Targeted Imaging and Therapy**

Husheng Yan1, Miao Guo1 and Keliang Liu2

*1Key Laboratory of Functional Polymer Materials, Ministry of Education, Institute of Polymer Chemistry, Nankai University, Tianjin, 2Beijing Institute of Pharmacology and Toxicology, Beijing, P. R. China* 

### **1. Introduction**

282 Biomedical Science, Engineering and Technology

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issued January 26, 2011

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Nanotechnology offers tremendous potential for use in biomedical applications, including imaging, disease diagnosis, and drug delivery. The development of nanosystems has improved the molecular understanding of many diseases and permitted the controlled nanoscale manipulation of materials (Couvreur & Vauthier, 2006). Nanomedical platforms offer many advantages as delivery, sensing, and image-enhancing agents. In recent years, many studies have focused on multifunctional nanomedical platforms that incorporate therapeutic and diagnostic agents with molecular targeting capabilities. Gregoriadis et al. first proposed liposomes as drug carriers in cancer chemotherapy in 1974 (Gregoria et al., 1974). Today, drug delivery systems made of lipids or polymers frequently are exploited for the controlled delivery of therapeutic drugs in the body (Jain, 2005; Vasir et al., 2005).

Nanosized particles for biomedical platforms can be made from a variety of materials, including lipids (liposomes, nanoemulsions, and solid-lipid nanoparticles), self-assembling amphiphilic molecules, nondegradable and degradable polymers, dendrimers, metals, and inorganic semiconductor nanocrystals. The selection of the platform material is determined by the desired diagnostic or therapeutic goal, payload type, material safety profile, and administration route. Among the various types of functional nanostructures, nanomedical platforms based on magnetic nanoparticles (MNPs) are of particular interest in biomedical applications. Most frequently, MNPs are constructed of superparamagnetic iron oxides (SPIOs) (e.g., Fe3O4 or γ-Fe2O3), although metals such as cobalt and nickel are also employed. The characteristics of MNPs, including their composition, size, morphology, and surface chemistry, are tailored by various processes for their wide application in the detection, diagnosis, and treatment of illnesses. The most popular MNPs for biomedical applications are comprised of a magnetic inorganic nanoparticle core and a biocompatible surface coating that provides stabilization under physiological conditions. The additional application of a suitable surface chemistry allows the integration of functional ligands, such that MNPs can perform multiple functions. The modification and functionalization of MNPs improve their magnetic properties and affect their behavior in vivo (Tartaj et al., 2003; A.K. Gupta & M. Gupta, 2005).

Multifunctional MNPs (MFMNPs) are a major class of nanoscale materials with the potential to revolutionize clinical diagnostic and therapeutic techniques. Due to their unique magnetic properties and ability to function at the cellular and molecular levels of biological interactions, MFMNPs have been investigated as an attractive nanomedical platform. MFMNPs in the form of SPIOs have been actively investigated as contrast enhancement agents for magnetic resonance imaging (MRI) and hyperthermia in response to an external alternating magnetic field, due to their ability to enhance the proton relaxation of specific tissues. MFMNPs have been evaluated extensively as a nanomedical platform for the targeted delivery of pharmaceuticals through magnetic drug targeting (Neuberger et al., 2005) and through the attachment of high-affinity ligands (Zhang et al., 2002; Torchilin, 2006).
