Real-time and non-invasive optical imaging of tumor-targeting glycol chitosan nanoparticles in various tumor models Jin Hee Na a, b, c , Heebeom Koo a , Sangmin Lee a, b , Kyung Hyun Min a, b , Kyeongsoon Park a , Heon Yoo d , Seung Hoon Lee d , Jae Hyung Park b, c , Ick Chan Kwon a , Seo Young Jeong b , Kwangmeyung Kim a, * a Biomedical Research Center, Korea Institute of Science and Technology, Hawolgok-dong, Seongbuk-gu, Seoul, South Korea b Department of Life and Nanopharmaceutical Sciences, Kyung Hee University, South Korea c Department of Chemical Engineering, College of Engineering, Kyung Hee University, South Korea d Neuro-Oncology Clinic, National Cancer Center, South Korea article info Article history: Received 17 March 2011 Accepted 29 March 2011 Available online 22 April 2011 Keywords: Tumor-targeting Nanoparticle Brain cancer Liver cancer Metastasis abstract Recently, various nanoparticle systems have been developed for tumor-targeted delivery of imaging agents or drugs. However, large amount of them still have insufficient tumor accumulation and this limits their further clinical applications. Moreover, the in vivo characteristics of nanoparticles have been largely unknown, because there are few proper technologies to achieve the direct and non-invasive characterization of nanoparticles in live animals. In this paper, we determined the key factors of nano- particles for in vivo tumor-targeting using our glycol chitosan nanoparticles (CNPs) which have proved their tumor-targeting ability in many previous papers. For this study, CNPs were labeled with near- infrared fluorescence (NIRF) dye, Cy5.5 for in vivo analysis by non-invasive optical imaging techniques. With these Cy5.5-CNPs, the factors such as in vitro/in vivo stability, deformability, and rapid uptake into target tumor cells and their effects on in vivo tumor-targeting were evaluated in various tumor-bearing mice models. In flank tumor models, Cy5.5-CNPs were selectively localized in tumor tissue than other organs, and the real-time intravascular tracking of CNPs proved the enhanced permeation and retention (EPR) effect of nanoparticles in tumor vasculature. Importantly, tumor-targeting CNPs showed an excellent tumor-specificity in brain tumors, liver tumors, and metastasis tumor models, indicating their great potential in both cancer imaging and therapy. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction One of the recent challenges in cancer diagnosis and therapy is the specific targeting of imaging agents or anticancer drugs to tumor site. In particular, cancer researchers have been extensively developing nanoparticles as nano-sized tumor-specific carriers which were liposomes, polymeric particles with natural or synthetic polymer, and inorganic particles (such as quantum dots, gold particles, and paramagnetic iron particles) [1,2]. This is based on the classical common consent that nanoparticles with the size of 100e200 nm are known to pass through fenestrate vessels by so- called the enhanced permeation and retention (EPR) effect, providing efficient accumulation in tumor tissues [1e3]. However, the in vivo results of tumor-targeting nanoparticles were not as good as the researchers expected from the in vitro studies, and this situation was probably because that the key factors that determine the tumor-specific targeting of nanoparticles are not fully under- stood [4]. If we examine the reported papers carefully, many studies have shown that the in vivo tumor-specificity of the developed nanoparticles was just slightly enhanced than the control drugs, because intravenously introduced nanoparticles are often non- specifically accumulated in normal tissues or quickly eliminated from the body by the immune system [5,6]. For the efficient delivery to target tumor tissues, the nano- particle system should present (a) prolonged circulation in blood flow, (b) reduced nonspecific uptake in normal tissues, and (c) rapid accumulation in target tumor tissues. In general, the size and surface chemistry of nanoparticles are known to greatly influence their in vivo tumor-targeting ability [7,8]. However, a number of nanoparticles with reasonable particle size and biocompatible surface were usually proven unsatisfactory during in vivo tests, due to their instability, short-period plasma circulation, and insufficient tumor-specific accumulation [9]. Therefore, there is still a room for * Corresponding author. Biomedical Research Center, Korea Institute of Science and Technology, Hawolgok-dong, Seongbuk-gu, Seoul, South Korea.Tel.: þ82 2 958 5921; fax: þ82 2 958 5909. E-mail address: kim@kist.re.kr (K. Kim). Contents lists available at ScienceDirect Biomaterials journal homepage: www.elsevier.com/locate/biomaterials 0142-9612/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2011.03.076 Biomaterials 32 (2011) 5252e5261