Journal of Photochemistry and Photobiology A: Chemistry 286 (2014) 55–63 Contents lists available at ScienceDirect Journal of Photochemistry and Photobiology A: Chemistry jo ur nal homep age: www.elsevier.com/locate/jphotochem Synthesis, spectroscopic properties and interaction with a liposomal membrane of a novel iodinated magnesium phthalocyanine Lukasz Lapok a,∗ , Małgorzata Cyza a , Arkadiusz Gut a , Mariusz K˛ epczy ´ nski a,∗ , Grzegorz Szewczyk b , Tadeusz Sarna b , Maria Nowakowska a a Faculty of Chemistry, Jagiellonian University, Ingardena 3, 30-060 Kraków, Poland b Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland a r t i c l e i n f o Article history: Received 29 January 2014 Received in revised form 3 April 2014 Accepted 5 April 2014 Available online 28 April 2014 Keywords: Phthalocyanine Photosensitizers Quantum yield of singlet oxygen formation Heavy atom effect PDT a b s t r a c t Phthalocyanines are applied as effective photosensitizers in photodynamic therapy of cancer and some other diseases. In this study, the synthesis of magnesium 2,9(10),16(17),23(24)-tetraiodophthalocyanine (2) is described. The spectroscopic, photophysical and photochemical parameters of phthalocyanine 2 are discussed, including the ability of this novel photosensitizer to generate singlet oxygen ( 1 O 2 ). The quantum yield of singlet oxygen formation (  ) was determined by two methods, viz. by measuring time-resolved phosphorescence at 1270 nm and by using 1,3-diphenylisobenzofuran and 9,10-dimethylanthracene, the well-known chemical acceptors. Applying the first method, the value of   in N,N-dimethylformamide was found to be 0.70 ± 0.02, while using the second method the quantum yield of singlet oxygen formation was found to be 0.95 ± 0.01. This discrepancy lead to the conclusion that the photooxidation process with phthalocyanine 2 as the photosensitizer proceeds via a mixed mechanism, viz. Type II and Type I and/or Type III. The fluorescence quantum yield of 2 in N,N- dimethylformamide is 0.063 ± 0.004. The interaction between photosensitizer 2 and liposomes in an aqueous suspension was studied using a laser scanning confocal microscopy and the fluorescence tech- nique. It was found that the binding constant of phthalocyanine 2 to liposomes was equal K b = 40.5 ± 6.4 (mg/mL) -1 . This implies, that the studied photosensitizer can readily penetrate cell or lipid membranes. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Conventional cancer treatment strategies, such as chemother- apy, radiotherapy, hormone therapy and surgery, suffer from severe side-effects including systemic toxicity or damage to healthy organs [1]. There is a need for less invasive cancer treatment technologies with significantly reduced side effects. A promising therapeutic procedures for the management of a variety of tumors is photodynamic therapy (PDT) [2]. This alternative therapy is a clinically approved method for the treatment of cancer, microbial infections, and some other diseases. PDT has proved effective in the treatment of malignancies of various organs, including lung, blad- der, gastrointestinal tract, and skin. It has also been effective in the therapy of bacterial infection of skin wounds and carious lesions [3]. This treatment modality involves intravenous or topical admin- istration of a photosensitizer, which after pre-determined time ∗ Corresponding authors. Tel.: +48 12 6632083; fax: +4812 6340515. E-mail addresses: lapok@chemia.uj.edu.pl, lukasz.a.lapok@gmail.com (L. Lapok), kepczyns@chemia.uj.edu.pl (M. K˛ epczy ´ nski). preferentially accumulates in the tumor tissue. Finally, the drug is activated with light of a suitable wavelength. Illumination with light triggers off the formation of singlet oxygen and other reactive oxygen species (ROS), which causes oxidative stress, resulting in damage of cellular membranes and other organelles, followed by death of cancer cells through apoptosis or necrosis [4]. A wide vari- ety of photosensitizers have been approved for PDT treatment in various countries [5]. These include: Photofrin (hematoporphyrin, the so-called “gold standard” in PDT), Tookad (palladium bac- teriopherophorbide), Foscan (meso-tetra-hydroxyphenylchlorine), Purlytin (tin ethyl etiopurpurin), Lutrin (lutetium motexafin), Lev- ulan (protoporphyrin IX) and many more [6]. They all can be classified as tetrapyrrolic and tripyrrolic dyes. Recently, photosensitizers that belong to the class of phthalo- cyanines [7], attracted considerable attention among researchers. Phthalocyanines are a group of organic dyes that are structurally related to the well-known porphyrins. However, unlike por- phyrins, they do not exist in nature and are available through the chemical synthesis only [8]. Phthalocyanines are well known for their distinct physicochemical properties such as: absorption of light in the range 600–700 nm; high molar extinction coefficient; http://dx.doi.org/10.1016/j.jphotochem.2014.04.006 1010-6030/© 2014 Elsevier B.V. All rights reserved.