Nitric Oxide Turn-on Fluorescent Probe Based on Deamination of Aromatic Primary Monoamines Tsun-Wei Shiue, † Yen-Hao Chen, † Chi-Ming Wu, ‡ Gyan Singh, † Hsing-Yin Chen, ‡ Chen-Hsiung Hung, § Wen-Feng Liaw, ∥ and Yun-Ming Wang* ,† † Department of Biological Science and Technology, Institute of Molecular Medicine and Bioengineering, National Chiao Tung University, 75 Bo-Ai Street, Hsinchu 300, Taiwan ‡ Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, 100 Shih-Chuan first Road, Kaohsiung 807, Taiwan § Institute of Chemistry, Academia Sinica, 128 Academia Road Sec. 2, Nankang, Taipei 115, Taiwan ∥ Department of Chemistry, National Tsing Hua University, 101 Kuang-Fu Road Sec. 2, Hsinchu 300, Taiwan * S Supporting Information ABSTRACT: The stable, water-soluble, and nonfluorescent FA- OMe can sense nitric oxide (NO) and form the intensely fluorescent product dA-FA-OMe via reductive deamination of the aromatic primary amine. The reaction is accompanied by a notable increase of the fluorescent quantum yield from 1.5 to 88.8%. The deamination mechanism of FA-OMe with NO was proposed in this study. The turn-on fluorescence signals were performed by suppression of photoinduced electron transfer (PeT), which was demonstrated by density functional theory (DFT) calculations of the components forming FA-OMe and dA-FA-OMe. Furthermore, FA-OMe showed water solubility and good stability at physiological pHs. Moreover, the selectivity study indicated that FA-OMe had high specificity for NO over other reactive oxygen/nitrogen species. In an endogenously generated NO detection study, increasing the incubation time of FA- OMe with lipopolysaccharide (LPS) pretreated Raw 264.7 murine macrophages could cause an enhanced fluorescence intensity image. In addition, a diffusion/localization cell imaging study showed that FA-OMe could be trapped in Raw 264.7 cells. These cell imaging results demonstrated that FA-OMe could be used as a turn-on fluorescent sensor for the detection of endogenously generated NO. 1. INTRODUCTION Nitric oxide (NO), produced by nitric oxide synthases in the biological systems, has been known as a ubiquitous signaling molecule. Despite being a simple molecule, NO is involved in diverse physiological and pathological pathways. 1 Although NO is a key vertebrate biological messenger, the mechanisms by which it performs its diverse biological roles remain elusive. In order to comprehend the diverse biological roles of NO, several techniques such as chemiluminescence, 2 colorimetry, 3 electron paramagnetic resonance, 4 electrochemistry, 5 and fluorimetry 6 have been developed. In view of its sensitivity, selectivity, spatiotemporal resolution, and experimental feasibility, fluorim- etry, which exploits fluorescent probes to monitor analytes of interest under a fluorescence microscope, has been regarded as a most promising method to detect endogenous NO. There have been a number of small-molecule organic or inorganic fluorescent NO sensors reported to date. 7 A two-component system comprised of an NO-reactive moiety coupling to an organic fluorophore has been widely investigated to develop NO-responsive organic molecule based sensors. The NO- reactive moiety acts as a modulator in the photoinduced electron transfer (PeT) mechanism. 8 After reaction with NO or the NO oxidized products, the PeT fluorescence quenching property is suppressed and the fluorescence of the probe is restored. The o-diaminophenyl group is the most commonly used NO-reactive moiety in organic fluorescent probes. 9 The electron-rich o-diaminophenyl group can react with NO under aerobic conditions to produce fluorescent triazole derivatives. However, there are some undesired handicaps, such as complicated and low-yield synthetic procedures and blank fluorescence, existing in these kinds of NO probes. In this study, the possibility of using an aromatic primary monoamine moiety as an NO-reactive site for the modulation of PeT was explored. The basic concept is outlined in Figure 1. The study was inspired by the genotoxic effects of NO. The NO-induced deamination of cytosine, adenine, guanine, and 5- methylcytosine indeed represents an important NO-induced genotoxic mechanism. 10 In addition, previous research reported that some aromatic amines react with NO or N 2 O 3 to give the Received: February 20, 2012 Published: April 9, 2012 Article pubs.acs.org/IC © 2012 American Chemical Society 5400 dx.doi.org/10.1021/ic300379u | Inorg. Chem. 2012, 51, 5400−5408