Reaction-Based Fluorescent Probes for the Detection and Imaging of Reactive Oxygen, Nitrogen, and Sulfur Species.

Xiaolong Sun,Adam C. Sedgwick,Steven D. Bull,Xiao-Peng He,Luling Wu,Tony D. James

doi:10.1021/acs.accounts.9b00302

Abstract

ConspectusThis Account describes a range of strategies for the development of fluorescent probes for detecting reactive oxygen species (ROS), reactive nitrogen species (RNS), and reactive (redox-active) sulfur species (RSS). Many ROS/RNS have been implicated in pathological processes such as Alzheimer’s disease, cancer, diabetes mellitus, cardiovascular disease, and aging, while many RSS play important roles in maintaining redox homeostasis, serving as antioxidants and acting as free radical scavengers. Fluorescence-based systems have emerged as one of the best ways to monitor the concentrations and locations of these often very short lived species. Because of the high levels of sensitivity and in particular their ability to be used for temporal and spatial sampling for in vivo imaging applications. As a direct result, there has been a huge surge in the development of fluorescent probes for sensitive and selective detection of ROS, RNS, and RSS within cellular environments. However, cellular environments are extremely complex, often with more than one species involved in a given biochemical process. As a result, there has been a rise in the development of dual-responsive fluorescent probes (AND-logic probes) that can monitor the presence of more than one species in a biological environment. Our aim with this Account is to introduce the fluorescent probes that we have developed for in vitro and in vivo measurement of ROS, RNS, and RSS. Fluorescence-based sensing mechanisms used in the construction of the probes include photoinduced electron transfer, intramolecular charge transfer, excited-state intramolecular proton transfer (ESIPT), and fluorescence resonance energy transfer. In particular, probes for hydrogen peroxide, hypochlorous acid, superoxide, peroxynitrite, glutathione, cysteine, homocysteine, and hydrogen sulfide are discussed. In addition, we describe the development of AND-logic-based systems capable of detecting two species, such as peroxynitrite and glutathione. One of the most interesting advances contained in this Account is our extension of indicator displacement assays (IDAs) to reaction-based indicator displacement assays (RIAs). In an IDA system, an indicator is allowed to bind reversibly to a receptor. Then a competitive analyte is introduced into the system, resulting in displacement of the indicator from the host, which in turn modulates the optical signal. With an RIA-based system, the indicator is cleaved from a preformed receptor–indicator complex rather than being displaced by the analyte. Nevertheless, without a doubt the most significant result contained in this Account is the use of an ESIPT-based probe for the simultaneous sensing of fibrous proteins/peptides AND environmental ROS/RNS.

Highlights

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are groups of reactive neutral and anionic small molecules that are produced within many cell types
“Turn on” fluorescent sensors are generally more useful for intracellular sensing applications because “turn off” fluorescent sensors can be quenched by off-target endogenous species to afford false-positive results. This led us to start developing sensors based on turn-on intramolecular charge transfer (ICT) fluorescence systems, which was achieved by the synthesis of a series of H2O2-responsive boronate esterbased fluorescence probes (Scheme 2)
We developed an NIR and colorimetric molecular probe based on a dicyanomethylene-4H-pyran (DCM) chromophore that facilitates the selective detection of GSH in living cells (HeLa) (Scheme 12)

Summary

■ INTRODUCTION

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are groups of reactive neutral and anionic small molecules that are produced within many cell types. “Turn on” fluorescent sensors are generally more useful for intracellular sensing applications because “turn off” fluorescent sensors can be quenched (nonspecifically) by off-target endogenous species to afford false-positive results This led us to start developing sensors based on turn-on intramolecular charge transfer (ICT) fluorescence systems, which was achieved by the synthesis of a series of H2O2-responsive boronate esterbased fluorescence probes (Scheme 2). The presence of ONOO− results in oxidative cleavage of the boronic ester fragment of the probe 3−D-fructose complex, which triggers a significant on−off fluorescence response (Scheme 7). Subsequent treatment of these brain sections with ONOO− generated the T* state of 3-HFOMe (Figure 6c, green channel) with regions of fluorescence once again correlated with anti-Aβ antibody fluorescence studies (Figure 6c, red channel) These highly promising biomacromolecular imaging results demonstrate how other ESIPT-based probes might potentially be used for simultaneous sensing of fibrous proteins/peptides AND environmental ROS/RNS. This system can be considered as a “reactive species” AND “environment” based fluorescent probe.[65]

■ CONCLUSIONS

■ ACKNOWLEDGMENTS

■ REFERENCES