A next-generation bifunctional photosensitizer with improved water-solubility for photodynamic therapy and diagnosis

// Hirotada Nishie 1 , Hiromi Kataoka 1 , Shigenobu Yano 2 , Jun-ichi Kikuchi 2 , Noriyuki Hayashi 1 , Atsushi Narumi 3 , Akihiro Nomoto 4 , Eiji Kubota 1 , Takashi Joh 1 1 Departments of Gastroenterology and Metabolism, Nagoya City University Graduate School of Medical Sciences, Mizuho-cho, Mizuho-ku, Nagoya 467-8601, Japan 2 Graduate School of Materials Science, Nara Institute of Science and Technology, Ikoma, Nara 630-0192, Japan 3 Department of Organic Materials Science, Graduate School of Organic Materials Science, Yamagata University, Yamagata, Yonezawa 992-8510, Japan 4 Department of Applied Chemistry, Graduate School of Engineering, Osaka Prefecture University, Nakaku, Sakai, Osaka 599-8531, Japan Correspondence to: Hiromi Kataoka, email: hkataoka@med.nagoya-cu.ac.jp Keywords: oligosaccharide-conjugated chlorin, Warburg effect, glycoconjugated chlorin, photodynamic therapy, photodynamic diagnosis Received: August 21, 2016 Accepted: September 23, 2016 Published: September 30, 2016 ABSTRACT Photodynamic therapy (PDT) exploits light interactions and photosensitizers to induce cytotoxic reactive oxygen species. Photodynamic diagnosis (PDD) uses the phenomenon of photosensitizer emitting fluorescence to distinguish some tumors from normal tissue. The standard photosensitizer used for PDD is 5-aminolevulinic acid (5-ALA), although it is not entirely satisfactory. We previously reported glucose-conjugated chlorin (G-chlorin) as a more effective photosensitizer than another widely used photosensitizer, talaporfin sodium (TS); however, G-chlorin is hydrophobic. We synthesized oligosaccharide-conjugated chlorin (O-chlorin) with improved water-solubility. We report herein on its accumulation and cytotoxicity. O-chlorin was synthesized and examined for solubility. Flow cytometric analysis was performed to evaluate O-chlorin accumulation in cancer cells. To evaluate the intracellular localization of photosensitizer, cells were stained with O-chlorin and organelle-specific fluorescent probes. We then measured the in vitro fluorescence of various photosensitizers and the half-maximal inhibitory concentrations to evaluate effects in PDD and PDT, respectively. Xenograft tumor models were established, and antitumor and visibility effects were analyzed. O-chlorin was first shown to be hydrophilic. Flow cytometry then revealed a 20- to 40-times higher accumulation of O-chlorin in cancer cells than of TS, and a 7- to 23-times greater fluorescence than 5-ALA. In vitro , the cytotoxicity of O-chlorin PDT was stronger than that of TS PDT, and O-chlorin tended to accumulate in lysosomes. In vivo , O-chlorin showed the best effect in PDT and PDD compared to other photosensitizers. O-chlorin was hydrophilic and showed excellent tumor accumulation and fluorescence. O-chlorin is promising as a next-generation bifunctional photosensitizer candidate for both PDT and PDD.