Detection Of HNO Research Articles

Decoding the enigmatic last gasotransmitter. The intriguing journey of HNO: From hidden origins to clues on reactivity and detection

This review focuses on HNO, a molecule of immense chemical and biological importance that has intrigued scientists for decades. Despite its elusive and transient nature, HNO may play an important role in various physiological processes, particularly in cardiovascular regulation. This review thoroughly examines the formation, chemical properties, and biological significance of HNO and highlights ongoing research efforts to unravel its mysteries. Challenges in studying HNO arise from its high reactivity, short half-life, and complex interactions with other nitrogen oxides, particularly nitric oxide. Detection and quantification of HNO in biological systems pose difficulties, prompting the development of advanced techniques. Active research into endogenous HNO formation is revealing intricate pathways within biological systems, the elucidation of which is crucial for exploiting its therapeutic potential. The multifaceted role of HNO in cardiovascular regulation, influencing vasorelaxation, blood pressure reduction, and enhanced cardiac contractility, underscores its profound impact on the circulatory system. Ongoing research holds promise for treating conditions such as hypertension and heart failure. As clinical applications expand, HNO research may unlock treatments for cardiovascular disease, inflammatory disorders, and cancer. The recent discovery of endogenous HNO production in plants adds a new dimension. While numerous clues have emerged, the scientific saga underscores that mysteries persist, evolve, and beckon to perpetual exploration in the realm of science.

A Near-Infrared Fluorescent Probe for the Rapid Detection of Nitroxyl in Living Cells.

Nitroxyl (HNO) plays an important role in various physiological activities. It has the potential to be used as a treatment for certain diseases such as alcohol poisoning, acute hypertension, and atherosclerosis. However, traditional methods for detecting HNO are challenging due to its rapid polymerization and elimination into N2O. Therefore, it is crucial to establish direct and effective HNO detection methods to comprehend these physiological processes better. In this study, a new near-infrared fluorescent probe called HXM-P based on the intramolecular charge transfer (ICT) mechanism was designed and synthesized. This probe employs 2-((6-hydroxy-2,3dihydro-1H-xanthen-4-yl)methylene)malononitrile as a fluorophore and 2-(diphenylphosphine) benzoate as a recognition group. The results showed that probe HXM-P can detect HNO with high sensitivity (1.07 × 10- 8 M). A good linear correlation was observed between the fluorescence intensities at 640nm and the concentrations of HNO in the range of 0-80 µM (R2 = 0.997). Moreover, probe HXM-P exhibited a rapid response rate (within 15s) toward HNO, and the fluorescent intensity reached a plateau within 5min, making it easier to track the highly reactive and short-lived HNO in living systems. Additionally, HXM-P was successfully employed for imaging HNO in HepG2 cells.

Reusable HNO Sensors Derived from Cu Cyclam: A DFT Study on the Mechanistic Origin of High Reactivity and Favorable Conformation Changes and Potential Improvements.

Nitroxyl (HNO) exhibits unique favorable properties in regulating biological and pharmacological activities. However, currently, there is only one Cu-based HNO sensor that can be recycled for reusable detection, which is a Cu cyclam derivative with a mixed thia/aza ligand. To elucidate the missing mechanistic origin of its high HNO reactivity and subsequent favorable conformation change toward a stable CuI product that is critical to be oxidized back by the physiological O2 level for HNO detection again, a density functional theory (DFT) computational study was performed. It not only reproduced experimental structural and reaction properties but also, more importantly, revealed an unknown role of the coordination atom in high reactivity. Its conformation change mechanism was found to not follow the previously proposed one but involve a novel favorable rotation pathway. Several newly designed complexes incorporating beneficial effects of coordination atoms and substituents to further enhance HNO reactivity while maintaining or even improving favorable conformation changes for reusable HNO detection were computationally validated. These novel results will facilitate the future development of reusable HNO sensors for true spatiotemporal resolution and repeated detection.

An activatable fluorescent-photoacoustic dual-modal probe for highly sensitive imaging of nitroxyl in vivo.

Nitroxyl (HNO) plays a vital role in various biological functions and pharmacological activities, so the development of an excellent near-infrared fluorescent (NIRF) and photoacoustic (PA) dual-modality probe is crucial for understanding HNO-related physiological and pathological progression. Herein, we proposed and synthesized a novel NIRF/PA dual probe (QL-HNO) by substituting an indole with quinolinium in hemicyanine for the sensitive detection of exogenous and endogenous HNO in vivo. The designed probe showed the highest sensitivity in NIRF mode and a desirable PA signal-to-noise ratio for HNO detection in vitro and was further applied for NIRF/PA dual-modal imaging of HNO with high contrast in living cells and tumor-bearing animals. Based on the excellent performance of QL-HNO, we believe that this study provides a promising molecular tool for further understanding of HNO-related physiological and pathological progression.

A robust ratiometric photoacoustic and fluorescence dual-modal molecular probe for capturing endogenous HNO generation in tumor mice model

HNO is reported in association with a wide variety of physiological and pathological states. However, photoacoustic (PA)/fluorescence (FL) dual-modal probes with complementary advantages for detection of HNO in living systems, especially in tumors, are still lacking. Herein, the first near-infrared (NIR) ratiometric PA/FL dual-modal probe (DOP-HNO), composed of a dual ratiometric molecular skeleton caged with 2-(diphenylphosphino)-benzoate group, was designed and synthesized for capturing endogenous HNO generation in vivo. DOP-HNO was able to specifically and sensitively respond to HNO with 4-fold ratiometric fluorescence enhancement (F783/F720) and 2.6-fold ratiometric PA enhancement (PA740/PA670). Moreover, DOP-HNO successfully visualized HNO fluctuations in 4T1 cells and living mice, and the crosstalk between NO and H2S in the tumors of living mice was clearly observed through NIR dual-ratiometric PA/FL imaging, indicating the accurate detection of HNO in vivo. More importantly, using DOP-HNO, for the first time, we provided the visualization evidence of endogenous HNO generation in cancer model and further investigated its possible generation mechanisms by H2S/NO interaction. Thus, we envision that the dual-modal probe DOP-HNO will be an effective tool to study the complex relationship between HNO and cancer as well as the pathology of other HNO-related diseases.

Light‐induced NO release from iron‐nitrosyl‐thiolato complex: The role of noncovalent thiol/thioether

AbstractFour low‐spin {FeNO}6 complexes, [Fe(NO)(PS2)(PS2H)] (1, PS2H2 = bis(2‐dimercaptophenyl)phenylphosphine) with a pendant thiol, [Fe(NO)(PS2)(PS2CH3)] (2) bearing a pendant thioether, and [Fe(NO)(PS2)(RPS)] (RH, 4a; RTMS, 4b) without the noncovalent thiol/thioether group are spectroscopically and structurally characterized. In comparisons of the νNO, absorption energy in UV/vis spectra and structural parameters from single X‐ray diffraction studies, the four iron‐nitrosyl‐thiolato compounds share similarity in electronic structure. Complex 1 with a pendant thiol leads to NO and HNO production upon exposure to the light. Photolysis of 2 bearing a pendant thioether only affords NO. Effective detection of HNO or NO from 1 or 2 is achieved by the employment of [MnIII(TMSPS3)(DABCO)]. In contrast, 4a and 4b show inertness toward visible‐light stimulus. Photolysis and having pendant thiol/thioether group play key roles in NO production from these iron‐nitrosyl‐thiolato complexes, that is, the Fe‐NO bond is weakened by exposure to light and the noncovalent SH of 1 or SCH3 of 2 can serve as an incoming ligand to interact with Fe atom, resulting in a transient with intramolecular [RS⋅⋅⋅Fe⋅⋅⋅NO] interaction (RH and CH3) which could facilitate NO dissociation.

A novel dansyl-naphthalimide fluorescent probe for visualizing nitroxyl (HNO) in biological systems

Nitroxyl (HNO), a kind of active nitrogen species, plays a vital role in particular physiological and pathological process. Urgent detection of HNO and understanding its biological roles in living systems is indispensable. Herein, we presented a novel dansyl-naphthalimide fluorescent sensor, NA-PA, for the selective response for HNO with remarkable fluorescence enhancement (ΦF = 32.5%) due to the hydrolysis of boronic pinacol ester. The proposed probe exhibited the desirable prominent features of high sensitivity, fast response, excellent selectivity and low cytotoxicity. Importantly, the probe works well in visualizing HNO in HepG-2 cells and live mice, illuminating that NA-PA would be a powerful tool to evaluate the physiological and pathological functions of HNO in life.

A near-infrared fluorescent probe with ultra-large Stokes shift for the detection of HNO in cells and mice

As one of the significant reactive nitrogen species in living systems, nitroxyl (HNO) plays a paramount role in a series of physiological and pathological processes. However, completely elucidating the role of endogenous HNO in living systems remains a huge challenge due to the lack of effective detection tools for the real-time monitoring of HNO. Recently, fluorescent probe has been widely accepted as a powerful molecular tool for the non-invasive detection of active species in living systems. Hence, in this work, we developed a new NIR fluorescent probe (N-HBT-HNO) with ultra-large Stokes shift for the effective detection and bioimaging of HNO in living cells and mouse. In the design blueprint of probe, the dicyanoisophorone moiety was integrated into the benzothiazole unit to expand the emission wavelength to NIR region of 728 nm and remarkably increase the Stokes shift to ultra large of 303 nm, which could endow the probe with superiority in bioimaging. Additionally, the 2-(diphenylphosphino) benzoate served as the efficient recognition group and fluorescence quenching group. Results demonstrated that the newly developed probe possessed appreciable sensing performance, including good selectivity, large signal to noise ratio, high sensitivity and fast response toward HNO. Subsequently, this probe was successfully applied for the bioimaging of exogenous HNO in living cells and mouse, reflecting the application potential of exogenous HNO (AS).

Solid-gas reactions for nitroxyl (HNO) generation in the gas phase

We present a novel nitroxyl (HNO) generation method, which avoids the need of using a liquid system or extreme experimental conditions. This method consists of the reaction between a gaseous base and an HNO donor (Piloty’s acid) in the solid phase, allowing the formation of gaseous HNO in a fast and economical way. Detection of HNO was carried out indirectly, measuring the nitrous oxide (N2O) byproduct of HNO dimerization using infrared spectroscopy, and directly, using mass spectrometry techniques and an electrochemical HNO sensor.

HNO to NO Conversion Mechanism with Copper Zinc Superoxide Dismutase, Comparison with Heme Protein Mediated Conversions, and the Origin of Questionable Reversibility.

The interconversion of NO and HNO, via copper zinc superoxide dismutase (CuZnSOD), is important in biomedicine and for HNO detection. Many mechanistic questions, including the decades-long debate on reversibility, were resolved in this work. Calculations of various active-site and full-protein models show that the basic mechanism is proton-coupled electron transfer with a computed barrier of 10.98 kcal mol-1 , which is in excellent agreement with experimental results (10.62 kcal mol-1 ), and this nonheme protein-mediated reaction has many significant mechanistic differences compared with the conversions mediated by heme proteins due to geometric and electronic factors. The reasons for the irreversible nature of this conversion and models with the first thermodynamically favorable and kinetically feasible mechanism for the experimental reverse reaction were discovered. Such results are the first for nonheme enzyme mediated HNO to NO conversions, which shall facilitate other related studies and HNO probe development.

A novel NIR fluorescent probe for the highly sensitive detection of HNO and its application in bioimaging

A “naked-eye” HNO probe based on xanthene was obtained.

A New Phenolate-Ion-Type Two-Photon Near Infrared Fluorophore-Based Biosensor for High-Performance Detection of HNO.

Although (E)-4-(2-(4-(dicyanomethylene)-4H-chromen-2-yl)vinyl)phenolate anion (DCPO- ) has recently emerged as a potential near infrared (NIR) biosensor signaling unit, the pKa value of its conjugate acid is relatively high (∼9); this will lead to relatively low concentrations of DCPO- under physiological conditions and, hence, unsatisfactory sensitivity of DCPO- -based bio-probes. By difluoro-substitution on DCPO- , we have exploited a new fluorophore of o-FDCPO- whose conjugate acid has a much lower pKa value of 7.42. Meanwhile, o-FDCPO- is NIR emissive with λem =693 nm and has a 0.76-fold higher fluorescence efficiency than DCPO- . The significant superiority of o-FDCPO- over DCPO- in sensitivity for NIR biosensor applications was confirmed by comparative studies on two HNO probes, namely o-FDCPO-P and DCPO-P, which bear signaling units of o-FDCPO- and DCPO- , respectively. Moreover, o-FDCPO-P has been demonstrated to be a high-performance HNO probe with high selectivity, high sensitivity (detection limit: 50 nm), and a rapid response, together with a two-photon NIR-excitation imaging capability.

A near-infrared fluorescent probe for imaging of nitroxyl in living cells.

A BODIPY-based NIR fluorescent probe, NitroxylBDP, for the rapid and specific, detection of HNO has been designed and synthesized. The merits of NIR fluorescence, and stable fluorescence output against pH changes, and good membrane permeability, enable the probe to serve as an ideal indicator for tracking HNO in living systems.

Response of inorganic Al12N12 nano-cage toward nitrosyl hydride: A computational study

The geometrical and electronic structures of adsorption of HNO on Al12N12 nanocage have been examined utilizing DFT computations by means of a (B3LYP-D) function with 6-31G* basis set. It was observed that HNO prefers to be adsorbed on the cage oxygen atom with −0.70 eV adsorption energy. This process of adsorption remarkably decreases the HOMO-LUMO gap (Eg) of the cage from 3.91 to 1.41 eV. The time-dependent density functional theory (TDDFT) indicates a high intensity peak in 390.29 nm in the steadiest complexes of HNO with Al12N12. The alteration in electronic attributes of the Al12N12 nanocage on adsorption of HNO is enough to consider it a potential sensor for the detection of HNO. The Al12N12 nanocage is Ф-type sensor and electronic sensor for HNO.

A two-photon fluorescent probe for HNO rapid visualization in endoplasmic reticulum

Nitroxyl (HNO) is a one-electron reduction product of nitric oxide (NO), which mainly exists in protonated form during physiological processes. As a kind of reactive nitrogen species (RNS), HNO has significant correlations with many physiological and pathological pathways. In this study, we report a two-photon fluorescent probeR2, which can detect HNO based on the reaction with a triarylphosphine group. Upon exposure to HNO, the probe R2 holds “naked eye” recognition, high selectivity and fast response (2 min). These excellent spectral properties promoted the detection of exogenous and endogenous HNO in MCF-7 cells. Furthermore, the probe could be selectively located in the endoplasmic reticulum (ER) with high biocompatibility and successfully apply to visualize NO/H2S cross-talk to generate HNO. These results support that R2 will provide a powerful tool to elucidate the physiological and pathological functions of HNO in the ER.

A novel dual-channel fluorescent probe for nitroxyl detection and its application in HepG-2 cells

Intracellular nitroxyl (HNO) acts as an essential intermolecular signal to regulate a wide variety of physiological and pathological processes. Nondestructive detection of HNO in living cells is an urgent need for further study of its physiological activity. In this work, we have developed a new probe LJ-3 for HNO detection with simultaneous response in green and NIR channels. Probe LJ-3 exhibited fast, large Stock's shift and sensitive response to HNO along with a distinct fluorescence change with maximum emission peak at 520 and 673 nm. The limit of detection of probe LJ-3 for HNO was calculated to be 111.6 nM. Furthermore, imaging studies taken in HepG-2 cells showed that LJ-3 could be employed as a dual-channel fluorescent probe for endogenous HNO detection and imaging in living system.

Recent Advances in Fluorescent Probes for Detection of HOCl and HNO.

It is known that reactive oxygen (ROS) and nitrogen (RNS) species play a diverse role in various biological processes, such as inflammation, signal transduction, and neurodegenerative injury, apart from causing various diseases caused by oxidative and nitrosative stresses, respectively, by ROS and RNS. Thus, it is very important to quantify the concentration level of ROS and RNS in live cells, tissues, and organisms. Various small-molecule-based fluorescent/chemodosimetric probes are reported to quantify and map the effective distribution of ROS/RNS under in vitro/in vivo conditions with a great spatial and temporal resolution. Such reagents are now appreciated as an excellent tool for aiding breakthroughs in modern redox biology. This mini-review is a brief, but all-inclusive, account of such molecular probes that have been developed recently.

A Ratiometric Upconversion Nanoprobe for Detection of HNO Based on Luminescence Resonance Energy Transfer

A Ratiometric Upconversion Nanoprobe for Detection of HNO Based on Luminescence Resonance Energy Transfer

Nitroxyl as a Potential Theranostic in the Cancer Arena.

Significance: As one-electron reduced molecule of nitric oxide (NO), nitroxyl (HNO) has gained enormous attention because of its novel physiological or pharmacological properties, ranging from cardiovascular protective actions to antitumoricidal effects. Recent Advances: HNO is emerging as a new entity with therapeutic advantages over its redox sibling, NO. The interests in the chemical, pharmacological, and biological characteristics of HNO have broadened our current understanding of its role in physiology and pathophysiology. Critical Issues: In particular, the experimental evidence suggests the therapeutic potential of HNO in tumor pharmacology, such as neuroblastoma, gastrointestinal tumor, ovarian, lung, and breast cancers. Indeed, HNO donors have been demonstrated to attenuate tumor proliferation and angiogenesis. Future Directions: In this review, the generation and detection of HNO are outlined, and the roles of HNO in cancer progression are further discussed. We anticipate that the completion of this review might give novel insights into the roles of HNO in cancer pharmacology and open up a novel field of cancer therapy based on HNO.

An isophorone-fused near-infrared fluorescent probe with a large Stokes shift for imaging endogenous nitroxyl in living cells and zebrafish.

Nitroxyl (HNO) plays an important role in multiple physiological and pathological processes, but the detailed generation mechanism of the endogenous HNO still remained to explore and perfect further. There is an urgent need to develop an excellent fluorescent probe for selective recognition and sensitive detection of HNO in biological systems. Near-infrared (NIR) fluorescent probes with a large Stokes shift are an ideal tool for bioimaging applications. Here, we have developed a NIR fluorescent probe with a large Stokes shift, namely, NIR-HNO, to monitor HNO in cells and zebrafish. NIR-HNO consists of an isophorone-fused NIR fluorescence reporter and a diphenylphosphinobenzoyl HNO-responsive unit. Based on an aza-ylide intramolecular ester aminolysis reaction, NIR-HNO showed a rapid selective NIR fluorescent turn-on response for HNO, high sensitivity (detection limit was 39.6 nM), and large Stokes shift (265 nm). The biological imaging results indicate that NIR-HNO is a good candidate for imaging of endogenous HNO in living systems.