Activatable red emitting fluorescent probe for rapid and sensitive detection of intracellular peroxynitrite

Construction of HPQ-based activatable fluorescent probe for peroxynitrite and its application in ferroptosis and mice model of LPS-induced inflammation

As one of the important members of reactive oxygen species, ONOO- plays a crucial role in signal transduction, immune response, and other physiological activities. Aberrant changes in ONOO- levels in the living organism are usually associated with many diseases. Therefore, it is important to establish a highly selective and sensitive method for the determination of ONOO- in vivo. Herein, we designed a novel ratio near-infrared fluorescent probe for ONOO- by directly conjugating dicyanoisophorone (DCI) to hydroxyphenyl-quinazolinone (HPQ). Surprisingly, HPQD was unaffected by environmental viscosity and responded rapidly to ONOO- within 40 s. The linear range of ONOO- detection was from 0 μM to 35 μM. Impressively, HPQD did not react with reactive oxygen species and was sensitive to exogenous/endogenous ONOO- in live cells. We also investigated the relationship between ONOO- and ferroptosis and achieved in vivo diagnosis and efficacy evaluation of mice model of LPS-induced inflammation, which showed promising prospects of HPQD in ONOO--related studies.

A mitochondria-targeted dual-response sensor for monitoring viscosity and peroxynitrite in living cells with distinct fluorescence signals

Viscosity and peroxynitrite (ONOO-) are two significant indicators to affect and evaluate the mitochondrial functional status, which are nearly relational with pathophysiological process in many diseases. Developing suitable analytical methods for monitoring mitochondrial viscosity changes and ONOO- is thus of great importance. In this research, a new mitochondria-targeted sensor DCVP-NO2 for the dual determination of viscosity and ONOO- was exploited based on the coumarin skeleton. DCVP-NO2 displayed a red fluorescence "turn-on" response toward viscosity along with about 30-fold intensity increase. Meanwhile, it could be used as ratiometric probe for detection of ONOO- with excellent sensitivity and extraordinary selectivity for ONOO- over other chemical and biological species. Moreover, thanks to its good photostability, low cytotoxicity and ideal mitochondrion-targeting capability, DCVP-NO2 was successfully utilized for fluorescence imaging of viscosity variations and ONOO- in mitochondria of living cells through different channels. In addition, the results of cell imaging revealed that ONOO- would lead to the increase of viscosity. Taken together, this work provides a potential molecular tool for researching biological functions and interactions of viscosity and ONOO- in mitochondria.

A long-wavelength mitochondria-targeted fluorescent probe for imaging of peroxynitrite during dexamethasone treatment

Peroxynitrite (ONOO^-), as a strong oxidizing reactive nitrogen substance (RNS), is generated endogenously by cells. Its visualization research is crucial to understand relevant disease processes. Herein, we reported a long-wavelength mitochondria-targeted fluorescence "turn on" probe TL. The probe TL could react with ONOO^- by using 4-(Bromomethyl)benzeneboronic as a reactive site, which exhibited outstanding characteristics for detection of ONOO^-, thus improving response time (about 50 s), sensitivity (DL, 10.1 nM), and emission wavelength (667 nm). Besides, TL displayed well mitochondria targeting and biological visualizing of exogenous and endogenous ONOO^- in biological systems. Finally, TL was used to monitor high concentration of dexamethasone-induced an up-regulation of ONOO^-. This indicated that TL has excellent potential to study the fluctuation of ONOO^- in the physiological and pathological system.

A novel "dual-locked" fluorescent probe for ONOO- and viscosity enables serum-based rapid disease screening

Peroxynitrite (ONOO^-) plays important roles in the progression of important disease such as inflammation, cancer, and diabetes, which made it an attractable target for biosensor development. However, to detect ONOO^- solely is highly dependent on the sensitivity of the detection method and may be disturbed by unwillingly false-positive signal. Cellular viscosity is an important microenvironmental parameter and its abnormal changes are closely related to diseases such as diabetes and cancer. In this case, to construct a "dual-locked" molecular tool for both ONOO^- and viscosity sensing and to evaluate the performance of such strategy in disease diagnosis is of great importance. We herein firstly reported the construction of a novel "dual-locked" probe DCI-OV which showed capability for simultaneous measuring ONOO^- concentration and system viscosity with high sensitivity (LOD = 4.7 nM) and high specificity. Moreover, both exogenous and low level of endogenous ONOO^- in living cells could be detected using DCI-OV due to viscosity amplified signal. Furthermore, cancer cells and insulin-resistant cells could be easily distinguished using DCI-OV. By taking advantage of the "dual-locked" sensing strategy, a total of 85 samples of human serum were screened using DCI-OV based rapid disease screening method and it was capable of differentiated and subdivided patients into specific type of disease, indicating the great potential of application of DCI-OV into clinical related disease diagnosis.

A highly selective probe for ratiometric imaging peroxynitrite in living cells and in vivo

In this study, we constructed and displayed a ratiometric fluorescent probe JQ-2 for detecting ONOO^-. The probe JQ-2 showed a ratiometric signal for visualizing ONOO^- with a rapid response and high selectivity over a panel of biological analytes. Moreover, the JQ-2 has near-infrared emission (657 nm), which provides an excellent basis for the practical application in biological systems. The probe JQ-2 possessed low cytotoxicity and excellent cell membrane permeability, which can specifically visualize the exogenous and endogenous ONOO^- in vitro and vivo by emission in two channels. Meanwhile, JQ-2 can be used for diagnosing drug-induced liver injury by visualizing and monitoring the fluctuations of endogenous ONOO^-. Therefore, JQ-2 provided a potential tool for precisely detecting the fluctuation of ONOO^- in biological systems to understand physiological and pathological process.

Photosensitized co-generation of nitric oxide and singlet oxygen Enhanced toxicity against ovarian cancer cells

Near micromolar concentrations of nitric oxide (NO) induce tumor cells death. However, an appropriate NO load has to be delivered selectively to the tumor site in order to avoid NO loss and secondary NO-induced effects. The encapsulation of millimolar concentrations of a NO source and an appropriate trigger of NO release within phospatidylcholine-based liposomes should provide an efficient tool for the selective release of the needed NO payload. In this work we report the photosensitized generation of singlet oxygen and NO from folate-targeted PEGylated liposomes, containing AlPcS4 as the sensitizer and S-nitrosoglutathione (GSNO), in millimolar amounts, as the NO source. Amounts of singlet oxygen detected outside the liposome when using PEGylated liposomes are near 200 % larger when GSNO is present inside the liposomes as compared to its absence. These liposomes, conjugated to folate, were found to enhance the photosensitized cytotoxicity to A2780CP20 ovarian cancer cells as compared to liposomes containing the sensitizer but no GSNO (30 % as compared to 70 % cell viability) under the conditions of this work. Fluorescense of AlPcS4 was observed inside cells incubated with folate-conjugated liposomes but not with liposomes without folate. The photosensitized activity enhancement by GSNO increased when light fluence or liposome concentration were increased. The majority of ovarian cancer patients are initially diagnosed with disseminated intra-abdominal disease (stages III-IV) and have a 5-year survival of less than 20%. This work suggests a novel ovarian cancer nodules treatment via the use of tumor-targeted liposome nanoparticles with the capability of generating simultaneously reactive oxygen and nitrogen species upon illumination with near-infrared light.

Neuroprotection Against NMDA-Induced Retinal Damage by Philanthotoxin-343 Involves Reduced Nitrosative Stress

N-methyl-D-aspartate receptor (NMDAR) overstimulation is known to mediate neurodegeneration, and hence represents a relevant therapeutic target for neurodegenerative disorders including glaucoma. This study examined the neuroprotective effects of philanthotoxin (PhTX)-343 against NMDA-induced retinal injury in rats. Male Sprague Dawley rats were divided into three groups; group 1 received phosphate buffer saline as the negative control, group 2 was injected with NMDA (160 nM) to induce retinal excitotoxic injury, and group 3 was pre-treated with PhTX-343 (160 nM) 24 h before NMDA exposure. All treatments were given intravitreally and bilaterally. Seven days post-treatment, rats were subjected to visual behaviour assessments using open field and colour recognition tests. Rats were then euthanized, and the retinas were harvested and subjected to haematoxylin and eosin (H&E) staining for morphometric analysis and 3-nitrotyrosine (3-NT) ELISA protocol as the nitrosative stress biomarker. PhTX-343 treatment prior to NMDA exposure improved the ability of rats to recognize visual cues and preserved visual functions (i.e., recognition of objects with different colours). Morphological examination of retinal tissues showed that the fractional ganglion cell layer thickness within the inner retina (IR) in the PhTX-343 treated group was greater by 1.28-fold as compared to NMDA-treated rats (p < 0.05) and was comparable to control rats (p > 0.05). Additionally, the number of retinal cell nuclei/100 μm² in IR for the PhTX-343-treated group was greater by 1.82-fold compared to NMDA-treated rats (p < 0.05) and was comparable to control group (p > 0.05). PhTX-343 also reduced the retinal 3-NT levels by 1.74-fold compared to NMDA-treated rats (p < 0.05). In conclusion, PhTX-343 pretreatment protects against NMDA-induced retinal morphological changes and visual impairment by suppressing nitrosative stress as reflected by the reduced retinal 3-NT level.

A novel p-dimethylaminophenylether-based fluorescent probe for the detection of native ONOO- in cells and zebrafish

Peroxynitrite (ONOO^-) is a highly reactive substance, and plays an essential part in maintaining cellular homeostasis. It is crucial to monitor the ONOO^- level in cells in normal and abnormal states. We introduced a p-dimethylaminophenylether-based fluorescent probe PDPE-PN, which could be synthesized readily. The new probe had prominent sensitivity and specificity, and a fast response towards ONOO^-. The spectral performance of probe PDPE-PN was outstanding and the limit of detection was 69 nM. Probe PDPE-PN with low toxicity was applied to detect endogenous/exogenous ONOO^- in RAW 264.7 macrophages and zebrafish. Importantly, successful application of the new receptor opens up new ideas for the design of ONOO^- probes.

A fluorescent probe for bioimaging of Hexosaminidases activity and exploration of drug-induced kidney injury in living cell

Hexosaminidases (Hexs) as an exoglycosidase participates in the catalytic hydrolysis of non-reducing end of glycoconjugates in the biological system. The fluctuation of Hexs level could cause many hereditary neurodegenerative diseases such as Tay-Sachs and Sandhoff. The Hexs activity is significantly up-regulated in colorectal cancer and kidney injury tissue so that it is particularly important to construct a fluorescent probe with significant signal change to understand its physiological role. In this work, DyOH was selected as fluorophore scaffolds to synthesize probe Hex-1 for detection of Hexs with good water solubility, high specificity, large stokes shift and quick response. Hex-1 can sensitively detect Hexs with the low detection limit (0.025 mU mL^-1) in vitro by "naked eye" due to superior spectral properties of DyOH. Furthermore, Hex-1 was not only employed for imaging Hexs in living cells with low toxicity, but also successfully applied to evaluate the fluctuation of Hexs activity during drug induced kindey injury in living HK-2 cells. These results indicated that Hex-1 could be used as a potential image tool to further explore the pathogenesis of kidney disease and cancer.

A mitochondria-targeted ratiometric fluorescent nanoprobe for imaging of peroxynitrite in living cells

Peroxynitrite (ONOO^-) is a series of basic biological oxidants involved in physiological and pathological processes. The detection of ONOO^- in biological systems has been challenging due to its extremely short half-life and low steady-state concentration. In this work, a ratiometric fluorescent nanoprobe for ONOO^- was constructed by coupling covalently of graphene quantum dots (GQDs) with cyanine 5.5 (Cy5.5). This nanoprobe (GQD-Cy5.5) could selectively accumulate in mitochondrial, appears two strong fluorescence emission peaks at 520 and 694 nm. In the presence of ONOO^-, the intensity of fluorescence emission peak at 520 nm increased and the intensity of fluorescence emission peak at 694 nm decreased. The ratio (F_{520 nm}/F_{694 nm}) of fluorescence intensity at two emission peaks had a good linear relationship with the concentration of ONOO^- in the range of 0-6.0 μM, and the detection limit was 0.03 μM. The excellent properties of the nanoprobe enable its applications in the ratiometric fluorescence imaging of endogenous ONOO^- in cell mitochondria.

A novel borate fluorescent probe for rapid selective intracellular peroxynitrite imaging

Peroxynitrite (ONOO^-) is one of the species of reactive nitrogen (RNS), which plays an important role in antibacterial activity and signal transduction and other physiological and pathological processes. In this paper, based on the benzyl borate group, a new fluorescent probe capable of detecting ONOO^- with high selectivity and sensitivity is designed, and the possible mechanism of the interaction between probe and ONOO^- is proposed. The probe shows high fluorescence response to ONOO^- in a wide pH range (7.0-11.5). Moreover, the probe exhibit good permeability, and the content of ONOO^- in cancer cells and normal cells was successfully monitored.