Semi-Quantitatively Designing Two-Photon High-Performance Fluorescent Probes for Glutathione S-Transferases

Abstract

<jats:p>Glutathione S-transferases (GSTs), detoxification enzymes that catalyze the addition of glutathione (GSH) to diverse electrophilic molecules, are often overexpressed in various tumor cells. While fluorescent probes for GSTs have often adopted the 2,4-dinitrobenzenesulfonyl (DNs) group as the receptor unit, they usually suffer from considerable background reaction noise with GSH due to excessive electron deficiency. However, weakening this reactivity is generally accompanied by loss of sensitivity for GSTs, and therefore, finely turning down the reactivity while maintaining certain sensitivity is critical for developing a practical probe. Here, we report a rational semiquantitative strategy for designing such a practical two-photon probe by introducing a parameter adopted from the conceptual density functional theory (CDFT), the local electrophilicity <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M1"><mml:msub><mml:mrow><mml:mi>ω</mml:mi></mml:mrow><mml:mrow><mml:mi>k</mml:mi></mml:mrow></mml:msub></mml:math>, to characterize this reactivity. As expected, kinetic studies established <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="M2"><mml:msub><mml:mrow><mml:mi>ω</mml:mi></mml:mrow><mml:mrow><mml:mi>k</mml:mi></mml:mrow></mml:msub></mml:math> as efficient to predict the reactivity with GSH, and probe NI3 showing the best performance was successfully applied to detecting GST activities in live cells and tissue sections with high sensitivity and signal-to-noise ratio. Photoinduced electron transfer of naphthalimide-based probes, captured by femtosecond transient absorption for the first time and unraveled by theoretical calculations, also contributes to the negligible background noise.</jats:p>

Fluorescent probes based on nucleophilic aromatic substitution reactions for reactive sulfur and selenium species: Recent progress, applications, and design strategies

“…Cleavage of the carbon-chalcogen bonds in phenyl-O ethers, phenyl-S ethers, and phenyl-Se ethers becomes increasingly facile as the atomic radius increases on going from oxygen to sulfur to selenium. In addition, the introduction of appropriate groups at different positions on the benzene ring can also modulate the ease of dissociation of phenyl ethers [153] , [154] , [155] .…”

“…The position of the introduced group on the benzene ring will affect the reactivity of the active site [155] , [161] , [267] . For example, introducing a nitro group on the benzene ring will increase the degree of dissociation of the active site.…”

“…The number of groups appended on the benzene ring will affect the reactivity of the active site [155] , [161] , [267] . At present, it is common to introduce doubly-substituted groups, such as 2,4-dinitrophenyl ether, 2,4-dinitrobenzenesulfonamide, 3,5-dinitrophenyl-O ether, 2-fluoro-4-nitrobenzoate, and so on.…”

“…Han et al used naphthalimide as the fluorophore and differently substituted benzenesulfonates as detection groups to screen and synthesize fluorescent probes for detecting GST activity ( Fig. 19 ) [155] . Probes similar to probe 55 – 1 proved to be ultra-sensitive.…”

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells

“…Conventional methods including sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS/PAGE), electrochemical assays, colorimetric assays, and bioluminescent sensors have been established for GSTs activity detection. , However, these methods suffer from disadvantages such as being time-consuming, requiring a lengthy preparation stage, high sample consumption, and lack of sensitivity. − Recently, luminescence imaging has emerged as a promising technique for the detection of disease-related proteins due to its high sensitivity, noninvasive modality, and dynamic measurement ability. − A range of fluorescent probes have been reported for GSTs based on the GSH nucleophilic substitution reaction catalyzed by GSTs, and these can be mainly divided into nitro group substitution reactions and sulfonyl cleavage reactions. ,− Luminescent transition complexes possess desirable photophysical properties (e.g., long emission lifetimes, high photostability, and wide Stokes shifts) which render them ideal imaging probes for biomolecules. − Very recently, the Yuan group developed a ruthenium­(II) complex for imaging GSTs in a drug-induced liver injury model based on a nitro group substitution reaction. , However, activity-based probes requiring the use of GSH may be susceptible to interference by metal ions and biomolecules in biological systems. Moreover, activity-based GSTs probes that depend heavily on nucleophilic substitution reactions are easily perturbed by the high concentration of nucleophilic molecules in the cellular environment, especially thiols (mM level). , …”