Synthesis and characterization of near IR fluorescent albumin nanoparticles for optical detection of colon cancer Sarit Cohen a , Michal Pellach a , Yossi Kam b , Igor Grinberg a , Enav Corem-Salkmon a , Abraham Rubinstein b, 1 , Shlomo Margel a, ⁎ a Department of Chemistry, Bar-Ilan Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, Ramat-Gan 52900, Israel b Institute for Drug Research, School of Pharmacy, Faculty of Medicine, The Hebrew University of Jerusalem, P.O. Box 12065, Jerusalem 91120, Israel abstract article info Article history: Received 13 July 2012 Received in revised form 16 October 2012 Accepted 13 November 2012 Available online 21 November 2012 Keywords: HSA nanoparticles Fluorescent nanoparticles NIR fluorescence NIR fluorescent albumin nanoparticles Optical imaging Near IR (NIR) fluorescent human serum albumin (HSA) nanoparticles hold great promise as contrast agents for tumor diagnosis. HSA nanoparticles are considered to be biocompatible, non-toxic and non-immunogenic. In ad- dition, NIR fluorescence properties of these nanoparticles are important for in vivo tumor diagnostics, with low autofluorescence and relatively deep penetration of NIR irradiation due to low absorption of biomatrices. The present study describes the synthesis of new NIR fluorescent HSA nanoparticles, by entrapment of a NIR fluores- cent dye within the HSA nanoparticles, which also significantly increases the photostability of the dye. Tumor-targeting ligands such as peanut agglutinin (PNA) and anti-carcinoembryonic antigen antibodies (anti-CEA) were covalently conjugated to the NIR fluorescent albumin nanoparticles, increasing the potential fluorescent signal in tumors with upregulated corresponding receptors. Specific colon tumor detection by the NIR fluorescent HSA nanoparticles was demonstrated in a chicken embryo model and a rat model. In future work we also plan to encapsulate cancer drugs such as doxorubicin within the NIR fluorescent HSA nanoparticles for both colon cancer imaging and therapy. © 2012 Elsevier B.V. All rights reserved. 1. Introduction It has become common knowledge that the early detection of colon cancer is the key to its survival. Early detection of adenoma- tous colonic polyps is also of major concern in the prevention of colon cancer [1–4]. Current techniques used for colon cancer screening include double-contrast barium enema, fecal occult blood tests and co- lonoscopy. These methods are considered to be either lacking in sensi- tivity or invasive, and colon cancer continues to be a major cause of death in the western world [5]. There is therefore a need for develop- ment of more effective methods for early detection of colonic tumors. Optical imaging techniques provide functional and anatomical characterization of biological tissues, revealing important informa- tion on significant physiological parameters [6]. While optical imag- ing based on white light allows observation of only superficial structures, fluorescence imaging allows for observation beyond the surface. Another advantage of fluorescence imaging compared to white-light technology is the high signal-to-noise ratio that can be achieved. However, significant autofluorescence of bodily tissues re- mains a limiting factor, with fluorescence imaging in the visible re- gion of the electromagnetic spectrum. Materials with fluorescence in the near-infrared (NIR) region (700–1000 nm) intended for use as imaging agents are of great interest, as they result in a lower back- ground signal and deeper penetration into biomatrices [7,8]. Nanoparticle-based NIR probes have been shown to have significant advantages over free organic NIR dyes such as enhanced photostability and biocompatibility, improved fluorescent signal (a large number of dye molecules per nanoparticle) and easy conjugation of biomolecules to functional groups on the nanoparticle surface [9]. Nanoparticles based on silica, calcium phosphate and lipoprotein containing NIR dyes have already been developed [10,11]. Tumors can be actively targeted by nanoparticles conjugated to molecular probes that recognize tumor-specific biomarkers. Known targeting agents include antibodies, lectins, small peptides and small targeting molecules, all with upregulated receptors on the tumor cell membrane. With targeting agents conjugated to the nanoparticles, the nanoparticles bind to specific cell-surface receptors, and are often uptaken into the cell via receptor-mediated endocytosis. The intracellu- lar concentration of nanoparticles is consequently enhanced in cancer cells compared to normal cells [12]. There is growing interest in the fabrication of albumin nanoparticles due to their biocompatibility, biodegradability and non-antigenicity. Materials Science and Engineering C 33 (2013) 923–931 ⁎ Corresponding author. Tel.: +972 3 5318861; fax: +972 3 6355208. E-mail address: shlomo.margel@mail.biu.ac.il (S. Margel). 1 Affiliated with the Harvey M. Krueger Family Center for Nanoscience and Nano- technology and the David R. Bloom Center of Pharmacy of the Hebrew University of Jerusalem. 0928-4931/$ – see front matter © 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.msec.2012.11.022 Contents lists available at SciVerse ScienceDirect Materials Science and Engineering C journal homepage: www.elsevier.com/locate/msec