Current Drug Delivery, 2011, 8, 59-69 59 1567-2018/11 $58.00+.00 © 2011 Bentham Science Publishers Ltd. Multifunctional Nanomedicine Platform for Cancer Specific Delivery of siRNA by Superparamagnetic Iron Oxide Nanoparticles-Dendrimer Complexes Oleh Taratula 1,2 , Olga Garbuzenko 1 , Ronak Savla 1,2 , Y. Andrew Wang 3 , Huixin He 2, * and Tamara Minko 1, * 1 Department of Pharmaceutics, Rutgers, The State University of New Jersey, Piscataway, NJ 08854, USA; 2 Department of Chemistry, Rutgers, The State University of New Jersey, Newark, NJ 07102, USA; 3 Ocean NanoTech, LLC Spring- dale, AR 72764, USA Abstract: The ability of Superparamagnetic Iron Oxide (SPIO) nanoparticles and Poly(Propyleneimine) generation 5 dendrimers (PPI G5) to cooperatively provoke siRNA complexation was investigated in order to develop a targeted, mul- tifunctional siRNA delivery system for cancer therapy. Poly(ethylene glycol) (PEG) coating and cancer specific targeting moiety (LHRH peptide) have been incorporated into SPIO-PPI G5-siRNA complexes to enhance serum stability and se- lective internalization by cancer cells. Such a modification of siRNA nanoparticles enhanced its internalization into cancer cells and increased the efficiency of targeted gene suppression in vitro. Moreover, the developed siRNA delivery system was capable of sufficiently enhancing in vivo antitumor activity of an anticancer drug (Cisplatin). The proposed approach demonstrates potential for the creation of targeted multifunctional nanomedicine platforms with the ability to deliver therapeutic siRNA specifically to cancer cells in order to prevent severe adverse side effects on healthy tissues and in situ monitoring of the therapeutic outcome using clinically relevant imaging techniques. Keywords: SPIO nanoparticles, PPI dendrimer, siRNA, Cisplatin, LHRH peptide, imaging, tumor targeting. INTRODUCTION The ability of short interfering RNA (siRNA) to silence specific genes inspired the use of siRNA as a therapeutic agent for a wide spectrum of disorders including cancer, in- fectious diseases, and metabolic disturbances [1-5]. The main advantages of RNA interference compared to other therapeutic approaches include exceptional specificity of siRNA, high potency of gene silencing, and the ability to target virtually any expressed gene [6, 7]. However, the low penetration ability of naked siRNA into the cellular cyto- plasm to induce sequence-specific mRNA degradation repre- sents a primary obstacle limiting the success of siRNA ther- apy [7-11]. Despite extensive research, an efficient, nontoxic gene delivery approach has not yet been developed. It is rec- ognized that the delivery of the nucleic acid by nanocarriers facilitates the cellular uptake of DNA/siRNA and increases their gene silencing ability [12-14]. Viruses have been stud- ied as gene delivery vectors; however, the immune response elicited by viral capsid proteins represents a major challenge limiting the wide use of this approach [15]. Consequently, considerable interest to the development of nonviral gene delivery vehicles has been generated. In order to provide effective gene silencing, two controversial requirements for *Address correspondence to these authors at the Department of Pharmaceu- tics, Ernest Mario School of Pharmacy, Rutgers, The State University of New Jersey, 160 Frelinghuysen Road, Piscataway, NJ 08854–8020; USA; Tel: 732-445-3831 x 214; Fax: 732-445-3134; E-mail: minko@rci.rutgers.edu and Department of Chemistry, Rutgers, The State of New Jersey, 73 Warren Street, Newark, NJ, 07102; USA; Tel: 973- 353-1254; Fax: 973-353-1264; E-mail: huixinhe@newark.rutgers.edu such delivery systems should be satisfied: (1) stability of siRNA carrier complex during its journey in the systemic circulation toward the targeted cells and the protection of the payload against the aggressive biological environment and (2) intracellular availability of the nucleic acids in order to permit desired therapeutic effects within the cells [8, 16-18]. In order to optimize the delivery of siRNA and enhance the efficiency of the treatment, it is highly desirable to em- ploy clinically relevant imaging approaches for in-situ moni- toring of the disease progression and therapeutic responses [12]. Magnetic Resonance Imaging (MRI) is a powerful tool for non-invasive in vivo monitoring due to its high resolution and lack of ionizing radiation [19, 20]. Superparamagnetic Iron Oxide (SPIO) nanoparticles have been widely investi- gated as MRI contrast agents to enhance images of biological molecules [21, 22]. Moreover, several approaches have been reported for both siRNA and DNA delivery based on SPIO nanoparticles to timely monitor the delivery process and also to evaluate the therapeutic effects [12, 23, 24]. However, these methods have various shortcomings and do not allow a balanced optimization of siRNA compaction, endosomal escape, and dissociation from the nanoparticles. For exam- ple, Medarova et al. [12] covalently linked siRNA molecules to the SPIO surface and demonstrated the feasibility of using SPIO nanoparticles as MRI enhancers for in vivo tracking of tumor uptake and silencing effects of the siRNA. However, siRNA molecules in this study are tethered to the nanoparti- cles through chemical bonds between the siRNA and SPIO nanoparticles. Consequently, it is highly possible that such chemical conjugations might potentially compromise the