A naphthalimide-based turn-on fluorescence probe for peroxynitrite detection and imaging in living cells

Small molecule probes for peroxynitrite detection

Peroxynitrite (ONOO‒/ONOOH) is a short-lived but highly reactive species that is formed in the diffusion-controlled reaction between nitric oxide and the superoxide radical anion. It can oxidize certain biomolecules and has been considered as a key cellular oxidant formed under various pathophysiological conditions. It is crucial to selectively detect and quantify ONOO- to determine its role in biological processes. In this review, we discuss various approaches used to detect ONOO‒ in cell-free and cellular systems with the major emphasis on small-molecule chemical probes. We review the chemical principles and mechanisms responsible for the formation of the detectable products, and plausible limitations of the probes. We recommend the use of boronate-based chemical probes for ONOO‒, as they react directly and rapidly with ONOO-, they produce minor but ONOO‒‒specific products, and the reaction kinetics and mechanism have been rigorously characterized. Specific experimental approaches and protocols for the detection of ONOO- in cell-free, cellular, and in vivo systems using boronate-based molecular probes are provided (as shown in Boxes 1-6).

Theoretical insights into a turn-on fluorescence probe based on naphthalimide for peroxynitrite detection

Compared with other reactive oxygen species, peroxynitrite (ONOO-) has diversified reactions and transformations in organisms, and its specific action mechanism is not very clear. The study of reactive oxygen species is of great significance in the field of physiology and pathology. Recently an effective on/off fluorescent probe HCA-OH was designed by Liu et al. through tethering p-aminophenol to 1,8-naphthalimide directly. The probe HCA-OH could release the fluorophore HCA-NH2 with good photostability and high fluorescence quantum yield under oxidation of ONOO- via dearylation process. In this work, the sensing mechanism and spectrum character of probe HCA-OH were studied in detail under quantum chemistry calculation. The electronic structures, reaction sites and fluorescent properties of the probe were theoretically analyzed to benefit us for in-depth understanding the principle of detection on reactive oxygen species (ONOO-) with the fluorescent probe HCA-OH. These theoretical results could inspire the medical research community to design and synthesize highly efficient fluorescent probe for reactive oxygen species detection.

Ex Tenebris Lux: Illuminating Reactive Oxygen and Nitrogen Species with Small Molecule Probes

Reactive oxygen and nitrogen species are small reactive molecules derived from elements in the air─oxygen and nitrogen. They are produced in biological systems to mediate fundamental aspects of cellular signaling but must be very tightly balanced to prevent indiscriminate damage to biological molecules. Small molecule probes can transmute the specific nature of each reactive oxygen and nitrogen species into an observable luminescent signal (or even an acoustic wave) to offer sensitive and selective imaging in living cells and whole animals. This review focuses specifically on small molecule probes for superoxide, hydrogen peroxide, hypochlorite, nitric oxide, and peroxynitrite that provide a luminescent or photoacoustic signal. Important background information on general photophysical phenomena, common probe designs, mechanisms, and imaging modalities will be provided, and then, probes for each analyte will be thoroughly evaluated. A discussion of the successes of the field will be presented, followed by recommendations for improvement and a future outlook of emerging trends. Our objectives are to provide an informative, useful, and thorough field guide to small molecule probes for reactive oxygen and nitrogen species as well as important context to compare the ecosystem of chemistries and molecular scaffolds that has manifested within the field.

A Phenanthrenequinone-Based Ratiometric Fluorescent Probe for Rapid Detection of Peroxynitrite with Imaging in Osteoblast Precursor Cells

In the current situation, peroxynitrite (ONOO-) is drawing the increasing attention of researchers for its pivotal role in diverse pathological and physiological processes on grounds of robust oxidation and nitrification. Herein, we have successfully designed and synthesized a phenanthrenequinone benzyl borate-based chemosensor for fast and selective detection of ONOO-. The probe PTDP itself had an orange fluorescence, which was changed to strong blue fluorescence upon the addition of ONOO-, indicating the ratiometric response of the probe. This is so because of the cleavage of the benzyl boronate-protecting group of PTDP upon the addition of ONOO- with simultaneous releasing of pyridinyl-based chemosensor PPI. The PTDP showed outstanding performance in the various photophysical studies such as good selectivity, excellent sensitivity with a very low detection limit of 2.74 nM, and a very fast response time (<15 s). Furthermore, for practical applicability, it was successfully applied in the ratiometric detection of ONOO- in osteoblast precursor cells.

New 1,8-naphthalimide-based colorimetric fluorescent probe for specific detection of hydrazine and its multi-functional applications

Detection of hydrazine is particularly important given its toxicity and extensive application in various industries. In the present paper, a colorimetric fluorescent probe NI-CIN based on 1,8-naphthalimide derivative was rationally designed and simply synthesized for specific detection of hydrazine based on the intramolecular charge transfer (ICT) mechanism. Upon the addition of hydrazine, a significant fluorescence enhancement at 556 nm could be observed within 4 min with a distinct color change from colorless to bright yellow, readily observed by naked eye. Except for HRMS and 1H NMR, density functional theory (DFT) calculations were also performed to support the sensing mechanism. In addition, eco-friendly paper test strips were easily prepared by NI-CIN for selective and real-time detection of hydrazine under aqueous and vapor phases. Furthermore, NI-CIN shows many potential applications for detecting hydrazine in real water and soil samples along with bio-imaging in HepG-2 cells and zebrafish.

Recent Progress of Spectroscopic Probes for Peroxynitrite and Their Potential Medical Diagnostic Applications

Peroxynitrite (ONOO-) is a crucial reactive oxygen species that plays a vital role in cellular signal transduction and homeostatic regulation. Determining and visualizing peroxynitrite accurately in biological systems is important for understanding its roles in physiological and pathological activity. Among the various detection methods, fluorescent probe-based spectroscopic detection offers real-time and minimally invasive detection, high sensitivity and selectivity, and easy structural and property modification. This review categorizes fluorescent probes by their fluorophore structures, highlighting their chemical structures, recognition mechanisms, and response behaviors in detail. We hope that this review could help trigger novel ideas for potential medical diagnostic applications of peroxynitrite-related molecular diseases.

A mitochondrion targetable dimethylphosphorothionate-based far-red and colorimetric fluorescent probe with large Stokes shift for monitoring peroxynitrite in living cells

Peroxynitrite (ONOO^-) is a biological oxidant that is related to numerous physiological and pathological processes. An overdose of ONOO^- is the cause of various serious diseases. Some evidence demonstrates that mitochondria are the major sites of ONOO^- production. Therefore, monitoring mitochondrial ONOO^- is important to understand the related pathological processes in living systems. Herein, a colorimetric and far-red fluorescent sensing probe (PCPA) for the determination of ONOO^- was constructed based on a dicyanoisophorone skeleton using dimethylphosphorothionate as the recognition group and pyridine salt as the mitochondrion-targeting unit. PCPA showed a far-red fluorescence response to ONOO^- accompanied by a distinct color change from colorless to yellow via the ONOO^- induced deprotection of dimethylphosphorothionate. In addition, PCPA exhibited a large Stokes shift (200 nm), high selectivity detection and high sensibility (LOD = 39 nM). Furthermore, PCPA was successfully employed for imaging ONOO^- and tracing ONOO^- in mitochondria. PCPA presents a new recognition group and has potential applications in the biology field.

Design of a naphthalimide-based probe for acrolein detection in foods and cells

Acrolein is a highly toxic agent that can be generated exogenously and endogenously. Therefore, a highly specific and sensitive probe for acrolein with potential applications in acrolein detection must be developed. In this research, a novel fluorescent probe named "probe for acrolein detection" (Pr-ACR) was designed and synthesized based on a naphthalimide fluorophore skeleton, and a thiol group (-SH) was introduced into its structure for acrolein recognition. The -SH traps acrolein via Michael addition and the resultant interaction product of the probe inhibits the photoinduced electron transfer process and produce a strong fluorescence at 510 nm. The probe showed high sensitivity and specificity for acrolein. HPLC-MS/MS analysis verified that it can be used to quantify acrolein in foods, such as soda crackers, red wine, and baijiu, with a fluorescence spectrophotometer. After methyl esterification, the methyl esterified probe (mPr-ACR) successfully visualised acrolein in Hela cells under a laser scanning confocal microscope. This finding proved that Pr-ACR and mPr-ACR are potential tools for the detection and visualisation of acrolein from different sources.

Phosphinate-benzoindocyanin fluorescent probe for endogenous mitochondrial peroxynitrite detection in living cells and gallbladder access in inflammatory zebrafish animal models

Potent oxidants such as peroxynitrite (ONOO^-) play important roles in the regulation of different physiopathological processes; their overproduction is thought to potentially cause several diseases in living organisms. Hence, the precise and selective monitoring of ONOO^- is imperative for elucidating its interplay and roles in pathological and physiological processes. Herein, we present a novel diphenyl phosphinate-masked benzoindocyanin "turn-on" fluorogenic probe to help detect mitochondrial ONOO^- in living cells and zebrafish models. A pale yellow color solution of BICBzDP turns rose-red upon the addition of ONOO^-_, selectively, contrary to that of other competitive bioactive molecules. BICBzDP displays an ultra-sensitivity detection limit (47.8 nM) with outstanding selectivity and sensitivity towards mitochondrial ONOO^- and possesses a notable 68-fold fluorescence enhancement involving a large redshift of 91 nm. Importantly, further biological experimental investigations with BICBzDP indicate specific sensitivity and reliability of the probe to track the ONOO^- level, not only in live cells, but also demonstrates dynamic fluctuations in the inflammatory zebrafish animal models. Thus, BICBzDP could be employed as a future potential biological tool for exploiting the role of ONOO^- in a variety of different physiological systems.