487 Macromolecular Research, Vol. 19, No. 5, pp 487-494 (2011) www.springer.com/13233 The Polymer Society of Korea Heparin-Based Self-Assembled Nanoparticles for Photodynamic Therapy Li Li †,1 , Hyun Tae Moon †,2 , Jin-Young Park 3 , Yu Jung Heo 3 , Yongdoo Choi 3 , Thanh Huyen Tran 1 , Yong-kyu Lee 4 , So Yeon Kim* , 5 , and Kang Moo Huh* , 1 1 Department of Polymer Science and Engineering, Chungnam National University, Daejeon 305-764, Korea 2 Mediplex Corp., Seoul 135-729, Korea 3 Molecular Imaging & Therapy branch, National Cancer Center, Goyang 410-769, Korea 4 Department of Chemical and Biological Engineering, Chungju National University, Chungju 380-702, Korea 5 Department of Chemical Engineering Education, Chungnam National University, Daejeon 305-764, Korea Received October 30, 2010; Revised December 1, 2010; Accepted December 2, 2010 Abstract: Novel heparin-based self-assembled nanoparticles were developed for photodynamic cancer therapy. A heparin-poly(β-benzyl-L-aspartate) (HP) amphiphilic copolymer was synthesized for effective delivery of a hydro- phobic photosensitizer, pheophorbide a (Pheo). The anti-coagulant activity of the HP copolymer decreased signifi- cantly, as measured by an anti-FXa chromogenic assay. Pheo was effectively incorporated into the HP nanoparticles using a dialysis technique. A good drug-loading content was obtained by altering the composition of the HP copoly- mer and Pheo/HP feed ratio. The Pheo-loaded HP nanoparticles had an average diameter of 117-189 nm, a nega- tively charged surface, and a sustained drug release pattern. These properties may allow them to passively target the tumor site through an enhanced permeability and retention (EPR) effect. Furthermore, the Pheo-loaded HP nanoparti- cles demonstrated marked photocytotoxicity and minimal darktoxic without a light treatment. The 6HP-Pheo15 nanoparticles were internalized into SCC7 cancer cells and damaged the cells after a light treatment. This suggests that HP nanoparticles have potential as an effective delivery system for clinical PDT. Keywords: self-assembled nanoparticles, photodynamic therapy, heparin, drug delivery. Introduction Photodynamic therapy (PDT) is a promising medical technology for treatment of cancers. PDT is based on the photochemical reaction mediated through the interaction of photosensitizers, light, and tissue oxygen. When photosen- sitizers accumulate in tumor tissue, they generate cytotoxic species upon photoactivation with light at appropriate wavelength, such as reactive oxygen species, which induces irreversible tumor cell destruction. 1-3 In addition to directly killing tumor cells by reactive oxygen species, PDT can damage the tumor-associated vasculature leading to tumor infarction, and can activate the immune response against tumor cells. 4-7 Because photosensitizers are typically harm- less without light, tumor site treatment can be precisely tar- geted by selective illumination, limiting damage to surrounding healthy tissues. However, the application of PDT for cancer treatment has been limited by the poor tumor selectivity. Nonspecific accumulation of photosensitizers at normal tissues such as skin is mainly due to the hydrophobic nature of almost cur- rent clinical or preclinical photosensitizers for photody- namic cancer therapy. 8-11 Formulation of photosensitizer with nano drug carriers, such as liposomes, 12,13 polysaccharide/ photosensitizer conjugates 14,15 and self-assembled nanopar- ticles 16-20 may address these limitations. In particular, self- assembled nanoparticles of amphiphilic copolymers may be suitable carriers for hydrophobic photosensitizers, due to their small size, good drug loading capacity, kinetic stability in vivo, and the potential for tumor targeting through enhanced permeability and retention (EPR) effect. 21-23 PDT is generally a local treatment method and not effective for cancer metastasis, 1 a limitation that may be addressed by combining anti-angiogenic therapy and PDT. 3,24 Heparin, a highly sulfated water-soluble polysaccharide, is a common injectable anticoagulant drug. 25,26 Recently, preclinical studies have shown that heparin has attractive antitumor activities via inhibition of VEGF- and bFGF- mediated tumor angiogenesis as well as inhibition of tumor metastasis. 27-30 Several heparin-based derivatives that syn- thesized by chemical conjugation with low molecular weight molecules, such as deoxycholic acid, have been developed DOI 10.1007/s13233-011-0505-9 *Corresponding Authors. E-mails: khuh@cnu.ac.kr or kimsy@cnu.ac.kr † L. Li and H. T. Moon contributed equally to this work.