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Theranostics 2013; 3(9):692-702. doi:10.7150/thno.5922 This issue Cite

Research Paper

Evaluation of Polymethine Dyes as Potential Probes for Near Infrared Fluorescence Imaging of Tumors: Part - 1

Nadine S. James¹, Yihui Chen¹, Penny Joshi¹, Tymish Y. Ohulchanskyy², Manivannan Ethirajan¹, Maged Henary³, Lucjan Strekowsk³, Ravindra K Pandey^{1 ✉}

1. Department of Molecular and Cellular Biophysics and Biochemistry, Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263;
2. Institute for Lasers, Photonics and Biophotonics, University at Buffalo, NY 14260.
3. Department of Chemistry, Georgia State University, Atlanta GA 30302, USA.

✉ Corresponding author: Ravindra K. Pandey, Ph. D., PDT Center, Cell Stress Biology, Roswell Park Cancer Institute, Buffalo, NY 14263, Tel: 716-845-3203, Fax: 716-845-8920.

Abstract

Near-infrared (NIR) organic dyes have become important for many biomedical applications, including in vivo optical imaging. Conjugation of NIR fluorescent dyes to photosensitizing molecules (photosensitizers) holds strong potential for NIR fluorescence image guided photodynamic therapy (PDT) of cancer. Therefore, we were interested in investigating the photophysical properties, in vivo tumor-affinity and fluorescence imaging potential of a series of heterocyclic polymethine dyes, which could then be conjugated to certain PDT agents. For our present study, we selected a series of symmetrical polymethine dyes containing a variety of bis-N-substituted indole or benzindole moieties linked by linear conjugation with and without a fused substituted cyclohexene ring. The N-alkyl side chain at the C-terminal position was functionalized with sulfonic, carboxylic acid, methyl ester or hydroxyl groups. Although, among the parent cyanine dyes investigated, the commercially available, cyanine dye IR783 (3) (bis-indole-N-butylsulfonate)-polymethine dye with a cyclic chloro-cyclohexene moiety showed best fluorescence-imaging ability, based on its spectral properties (λ_Abs=782 nm, λ_Fl=810 nm, ε = 261,000 M^-1cm^-1, Φ_Fl≈0.08) and tumor affinity. In addition to 3, parent dyes IR820 and Cypate (6) were also selected and subjected to further modifications by introducing desired functional groups, which could enable further conjugation of the cyanine dyes to an effective photosensitizer HPPH developed in our laboratory. The synthesis and biological studies (tumor-imaging and PDT) of the resulting bifunctional conjugates are discussed in succeeding paper (Part-2 of this study).

Keywords: Photodynamic therapy, Near Infrared Fluorophores, Reactive Oxygen Species, Near Infrared Fluorescence Imaging, Fluorescence Quantum Yields.

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