Advancement of Fluorescent Methods for Detection of Nitric Oxide

Review Article

Austin J Biosens & Bioelectron. 2015;1(1): 1003.

Advancement of Fluorescent Methods for Detection of Nitric Oxide

New SY*

1School of Environmental and Biological Engineering, Nanjing University of Science & Technology, China

2Chemistry Department, University of South Florida, USA

*Corresponding author: Jinming Kong, School of Environmental and Biological Engineering, Nanjing University of Science & Technology, 210094 Nanjing, PR China.

Xueji Zhang, Chemistry Department, College of Arts and Sciences, University of South Florida, East Fowler Ave, Tampa, Florida 33620-4202, USA.

Received: September 30, 2014; Accepted: January 29, 2015; Published: February 02, 2015

Abstract

Biologically Nitric Oxide (NO) is an important inorganic compound involved in numerous signaling pathways, which has promoted the demand for analytical methods for detection of NO. Fluorescent sensing, more effective than any other detection methods, enables monitoring NO in physiological environments such as cell and blood. Fluorescent probes based detection methods have wide applications in selective and sensitive monitoring of NO production in vivo. In this review, we highlight the novel fluorescent NO sensors developed in recent years, including fabrication, analytical characteristics and biological applications.

Keywords: Nitric oxide; Fluorescent probes; Photo induced electron transfer; Reactive nitrogen and oxygen species

Abbreviations

NO: Nitric Oxide; DAFs: Diaminofluoresceins; DANs: Diaminonaphthalenes; DARs: Diaminorhodamines; SWNT: Single- Walled Carbon Nanotube; QDs: Quantum Dots; PET: Photo induced Electron Transfer; FRET: Fluorescence Resonance Energy Transfer; RNOS: Reactive Nitrogen And Oxygen Species; RH: Rhodamine B Hydrazide; RB: Rhodamine B; RBSe: Rhodamine B Selenolactone; DHA: Dehydroascorbic Acid; AA: Ascorbic Acid; iNOS: inducible NO Synthase; IFN-γ: Interferon-γ; LPS: Lipopolysaccharide; SN: Seminaphthofluorescein; CS: Chitosan; DMS: Dimethyl Sulfate; H3TCA: Tricarboxytriphenylamine; PMOFs: Porous Metal-Organic Frameworks; NIR: Near-Infrared; HEX-DMA: 1,6-hexanedioldimethacrylate; PMMA: Poly (methyl methacrylate); mHP: Modified Hyperbranched Polyether; NTPED: N-(3-(Trimethoxysilyl) propyl) ethylenediamine; CA: Cellulose Acetate; DTC: N-(dithiocarbaxy) sarcosine

Introduction

Although NO is well known as an environmental pollutant generated from incomplete combustion of molecules containing nitrogen, it is also important in human body at the concentration ranging from sub-nanomolar to micro molar levels. Furchgott, Ignarro and Murad reported in 1987 that NO is the endotheliumderived relaxation factor and they ultimately shared the Nobel Prize in Physiology in 1998 [1]. Hereafter, many researchers have continued to explore the unknown domains of NO. NO is now understood to be active in several physiological events taking place in cardiovascular, immune, nervous systems as well as pathological processes, [2] for example, arteriolosclerosis [3] and hypertension [4] are connected with underproduction of NO while cancer [5] and diabetes [6] are related to its overproduction. NO is biosynthesized endogenously by nitric oxide Synthase which is a heme-containing enzyme and catalyzes L-arginine to L-citrulline. It is widespread in mammals, plants, bacteria and invertebrates [7]. NO released exogenously has been found to result in various biological responses such as platelet activation decrease [8] and microbial viability reduction [9]. NO diffuses rapidly with an average lifetime from milliseconds to seconds.

Great attention for NO and its biological roles have prompted the development of analytical techniques for its detection and quantification. The effect of NO depends on its widely varying concentration in human body, ranging from sub-nanomolar to micro molar levels. NO can react with oxygen, thiol, heme and so on, thus it has short half-life which is typically less than 10 seconds in biological environment [10]. Consequently, methods with adequate sensitivity and high affectivity are required in NO detection. Moreover, high selectivity for NO over interfering species is also necessary due to the complexity of biological systems.

The majority of NO detection approaches can be classified into electrochemical and spectroscopic methods. Most electrochemical NO detection methods involve electro reduction, direct electro oxidation and catalytic electro oxidation [11]. Spectroscopy methods involve either indirect detection of byproducts (i.e. Griess reaction, chemiluminescence) or direct detection of adducts (i.e. absorbance, electron paramagnetic resonance spectroscopy, fluorescence) [12,13]. However, most of these methods suffer from problems with selectivity and sensitivity as well as disadvantages for NO detection in vivo as a result of the toxicity and the complex processes. By contrast, fluorescent method which is commonly used for intracellular detection of NO shows many excellent characteristics such as lowcost, high selectivity and sensitivity. Fluorescent probes can respond in direct and selective manners to NO. As such, they provide a valuable approach to explore the generation, accumulation and translocation of NO in biology with both spatial and temporal resolution [14].

The majority of NO detection approaches can be classified into electrochemical and spectroscopic methods. Most electrochemical NO detection methods involve electro reduction, direct electro oxidation and catalytic electro oxidation [11]. Spectroscopy methods involve either indirect detection of byproducts (i.e. Griess reaction, chemiluminescence) or direct detection of adducts (i.e. absorbance, electron paramagnetic resonance spectroscopy, fluorescence) [12,13]. However, most of these methods suffer from problems with selectivity and sensitivity as well as disadvantages for NO detection in vivo as a result of the toxicity and the complex processes. By contrast, fluorescent method which is commonly used for intracellular detection of NO shows many excellent characteristics such as lowcost, high selectivity and sensitivity. Fluorescent probes can respond in direct and selective manners to NO. As such, they provide a valuable approach to explore the generation, accumulation and translocation of NO in biology with both spatial and temporal resolution [14]. the past decades, numerous fluorescent probes for effective DNA detection have been explored and the commonly used probes can be classified into organic probes (i.e., Diaminofluoresceins (DAFs), [17-21] Diaminonaphthalenes (DANs), [22-24] Diaminorhodamines (DARs), [25] DAMBO-PH. [26]), metal complex-based probes (i.e., copper, [27,28] ferrum, [29] cobalt, [30] ruthenium, [31] dirhodium [32] complexes), Single-Walled Carbon Nanotube (SWNT) -based probes [33] and Quantum Dots (QDs) -based probes [33]. These fluorescent probes have excellent selectivity, high sensitivity and low toxicity for NO sensing in vivo [34-38]. The team led by Lippard has focused on several kinds of these fluorescent probes and reviewed all the commonly used probes before [31,33,39]. This review highlights the novel fluorescent NO sensors in recent years.

Fluorescent methods for detection of NO

In the past few years, the fluorescent methods for detection of NO are mainly based on Photo induced Electron Transfer (PET), Fluorescence Resonance Energy Transfer (FRET) and fluorescence response to ring-opened or ring-closed reaction. On the other hand, the fluorescent methods can also be classified into organic probesbased methods, metal complex probes-based methods, SWNT probesbased methods and QD probes-based methods. These fluorescent methods have excellent selectivity and sensitivity for NO and are available for different applications. In addition, these new-developed methods are more advantageous than the methods commonly used before in various aspects.

Organic probes-based methods

Numerous fluorescent methods for NO detection employ the probes with electron-rich o-phenylenediamine fraction. The introduction of o-phenylenediamine fraction in a fluorophore results in PET from the lone-pair electrons of amine to the fluorophore to quench the fluorescence. Conversion of the o-phenylenediamine to electron-poor aryltriazole in the presence of NO decreases the energy of lone-pair electrons and turns off the PET to restore fluorescence [39].

A typical example is the method employing Lyso-NINO, a lysosome-specific and two-photon fluorescent probe which has lower cytotoxicity, excellent lysosomal localization, high selectivity and sensitivity for monitoring endogenous and exogenous NO in lysosomes of macrophage cells [40]. Lyso-NINO based on PET is integration of lysosome-targeting (aminoethyl)morpholine, two-photon fluorophore naphthalimide and NO-capturing o-phenylenediamine. o-Phenylenediamine is employed not only as NO-captor but also as a fluorescence quencher for naphthalimide. In the lysosomal pH ranging from 4.5 to 5.5, Lyso-NINO exhibits weak fluorescence while the reaction conduct Lyso-NINO-T of Lyso-NINO with NO shows strong fluorescence (Figure 1). In addition, the photo properties of Lyso-NINO are not interfered by the byproducts of NO in lysosomes. Flow cytometry can be used for quantitative analysis of endogenous NO and iNOS inducers can effectively increase endogenous NO. Another example is a quinoline derivative QNO, a two-photon fluorescent probe composed of a glycinamide linker, an o-phenylenediamine and a quinoline derivative [41]. It also has characteristics such as good photo stability, low cytotoxicity and pH insensitivity. QNO itself exhibit very weak fluorescence because of PET. A triazine fraction is formed after the rapid reaction with NO, the PET is inhibited and the fluorescence is restored without any shift in wavelength (Figure 2). QNO exhibits high selectivity for NO over other biologically Reactive Nitrogen and Oxygen Species (RNOS). DANPBO-H [42] and DANPBO-M [43] are also o-phenylenediamine-based probes. The incorporation of two tetrahydronaphthalene with the pyrrole moiety of BODIPY [44] has extended the excitation and emission wavelengths as well as increased the lipophilicity. The probes have excellent intracellular retention because of their strong lipophilicity. Even under the irradiation of xenon lamp over 24h, the fluorescence intensity of the probes remains unchangeable. Their good photo stability is ensured by that the probes have no heavy atoms and withdrawing groups. DANPBOs themselves have very weak fluorescence at pH above 4, however, they react with NO to generate triazoles DANPBO-Ts with high fluorescence. Other biologically RNOS have no obvious interference with NO detection. A similar probe BOPB [45] has been also reported to be utilized for NO detection (Figure 3). Such kind of probes with o-phenylenediamine fraction react with NO indirectly, thus these methods are possibly irreversible and inaccurate.