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Open AccessArticle

A Classic Near-Infrared Probe Indocyanine Green for Detecting Singlet Oxygen

by Cheng-Yi Tang 1,2,†, Feng-Yao Wu 1,†, Min-Kai Yang 1, Yu-Min Guo 1, Gui-Hua Lu 1,2 and Yong-Hua Yang 1,2,*
State Key Laboratory of Pharmaceutical Biotechnology, NJU-NJFU Joint Institute of Plant Molecular Biology, School of Life Sciences, Nanjing University, Nanjing 210093, China
Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, China
Author to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editor: Michael R. Hamblin
Int. J. Mol. Sci. 2016, 17(2), 219;
Received: 13 January 2016 / Revised: 2 February 2016 / Accepted: 3 February 2016 / Published: 6 February 2016
(This article belongs to the Special Issue Advances in Photodynamic Therapy)
The revelation of mechanisms of photodynamic therapy (PDT) at the cellular level as well as singlet oxygen (1O2) as a second messengers requires the quantification of intracellular 1O2. To detect singlet oxygen, directly measuring the phosphorescence emitted from 1O2 at 1270 nm is simple but limited for the low quantum yield and intrinsic efficiency of 1O2 emission. Another method is chemically trapping 1O2 and measuring fluorescence, absorption and Electron Spin Resonance (ESR). In this paper, we used indocyanine green (ICG), the only near-infrared (NIR) probe approved by the Food and Drug Administration (FDA), to detect 1O2 in vitro. Once it reacts with 1O2, ICG is decomposed and its UV absorption at 780 nm decreases with the laser irradiation. Our data demonstrated that ICG could be more sensitive and accurate than Singlet Oxygen Sensor Green reagent® (SOSG, a commercialized fluorescence probe) in vitro, moreover, ICG functioned with Eosin Y while SOSG failed. Thus, ICG would reasonably provide the possibility to sense 1O2 in vitro, with high sensitivity, selectivity and suitability to most photosensitizers. View Full-Text
Keywords: singlet oxygen (1O2); indocyanine green (ICG) singlet oxygen (1O2); indocyanine green (ICG)
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Tang, C.-Y.; Wu, F.-Y.; Yang, M.-K.; Guo, Y.-M.; Lu, G.-H.; Yang, Y.-H. A Classic Near-Infrared Probe Indocyanine Green for Detecting Singlet Oxygen. Int. J. Mol. Sci. 2016, 17, 219.

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