A simple highly selective probe for discriminative visualization of endogenous cysteine, homocysteine and glutathione in living cells via three separated fluorescence channels

A near-infrared fluorescent probe with a large Stokes shift for the detection and imaging of biothiols in vitro and in vivo

In this study, a new near-infrared (NIR) fluorescent turn-on probe featuring a large Stokes shift (198 nm) was developed for the detection of biothiols. The probe was based on a dicyanoisophorone derivative serving as the fluorophore and a 2,4-dinitrobenzenesulfonyl (DNBS) group functioning as both a recognition site and a fluorescence quencher. In the absence of biothiols, the fluorescence of the probe was low due to the photoinduced electron transfer (PET) effect between the fluorophore and DNBS. Upon the presence of biothiols, the DNBS group underwent a nucleophilic aromatic substitution reaction with the sulfhydryl group of biothiols, leading to the release of the fluorophore and a notable emission peak at 668 nm. This developed probe exhibited exceptional selectivity and sensitivity to biothiols in solution, with an impressive detection limit of 28 nM for cysteine (Cys), 22 nM for homocysteine (Hcy), and 24 nM for glutathione (GSH). Furthermore, the probe demonstrated its applicability by successfully visualizing both endogenous and exogenous biothiols in living systems.

Simultaneous detection of cysteine and glutathione in food with a two-channel near-infrared fluorescent probe

L-Cysteine (Cys) and glutathione (GSH) are closely related biological species that widely exist in food and living cells. To simultaneously detect Cys and GSH from different emission channels, we developed a fluorescent probe (BDP-NBD) based on near-infrared BODIPY and 7-nitrobenzofurazan (NBD). Upon nucleophilic substitution reaction with GSH, BDP-NBD generated an emission band at 713 nm, which can be used to determine GSH (0-100 μM) with a low detection limit (34 nM). Different from GSH, BDP-NBD underwent a nucleophilic substitution-rearrangement reaction with Cys, affording two emission bands at 550 nm and 713 nm, respectively. BDP-NBD was successfully employed to quantify Cys and GSH in various food samples with good recoveries (86.6%-104.6%). Besides, BDP-NBD can image Cys and GSH in living cells from two emission channels. Therefore, this work developed a tool for the simultaneous determination of Cys and GSH in both food and living cells so as to ensure food safety and human health.

Development of fluorescent probes with specific recognition moiety for hydrogen polysulfide

Hydrogen polysulfide (H2Sn, n > 1) is an important component of reactive sulfur species (RSS), which is an important substance for maintaining the redox balance in cells. However, limited recognition moieties are available for hydrogen polysulfide probe design. In this study, we have constructed a small library containing several organic molecules to explore a new specific recognition moiety for H2Sn fluorescent probe design. To validate the discovery, two fluorescent probes, 7 and BCC, were further developed based on coumarin and its derivative. The probes exhibited desirable specificity for H2Sn monitoring, which can be used for detecting H2Sn in solution and cells. The new specific recognition moiety for H2Sn fluorescent probe design discovered in this work has certain guiding significance for development of H2Sn probes exploring biological roles in the future.

A red-emitting ultrasensitive fluorescent probe for specific detection and biological visualization of cysteine in vitro and in vivo

Developing efficient strategies for specific detection of cysteine (Cys) is of great importance for identifying complicated biological roles in physiological and pathological processes. Herein, an ultrasensitive red-emission fluorescent probe (termed 1) is constructed for specific detection and biological visualization of Cys. The linked-anthocyanin fluorophore modified with a twisted N, N-diethylamino moiety shows improved red-shifted emission (642 nm) and absolute quantum yield (0.224 in dimethyl sulfoxide), as well as minimal fluorescence background signal and good water solubility. Meanwhile, utilizing acryloyl chloride as recognition group endows the probe 1 with excellent sensitivity and selectivity towards Cys (limit of detection: 2.93 nM). More importantly, the in vitro and in vivo results confirm that the probe 1 has the capacity of fluorescence imaging of Cys and good biological safety, which holds great promise for bioanalysis and biosensing of Cys.

2-Mercaptobenzimidazole Functionalized Copper Nanoparticles Fluorescence Probe for Sensitivity and Selectivity Detection of Cys in Serum

In this paper, a 2-mercaptobenzimidazole-copper nanoparticles (MBI-CuNPs) fluorescent probe with high performance based on 2-mercaptobenzimidazole functionalized copper nanoparticles was synthesized by a hydrothermal method and used for cysteine (Cys) detection in serum. The MBI-CuNPs probe exhibits strong fluorescence emission at 415 nm under the excitation at 200 nm, which is attributed to the metal-ligand charge transfer (MLCT) transition through the coordination of an MBI ligand and monovalent copper. Furthermore, the MBI-CuNPs probe has a high quenching fluorescence response to Cys, and shows a good linearity relationship with Cys in 0.05-65 µM, with a detection limit of 52 nM. Moreover, the MBI-CuNPs probe could eliminate the interference of biological mercaptan Hcy and GSH with a similar structure and reaction properties, due to the strong electron-donating ability of Cys, which can quench the fluorescence of the MBI-CuNPs probe. The MBI-CuNPs probe was applied to the analysis of Cys in real serum, and the absolute recovery rate was as high as 90.23-97.00%. Such a fluorescent probe with high sensitivity and selectivity has potential applications for the early prevention of various diseases caused by abnormal Cys levels.

A high-performance fluorescent probe for detection of cysteine in plasma constructed by combining Cu(I) and 2,5-dimercapto-1,3,4-thiadiazole

A high-performance fluorescent probe 2,5-dimercapto-1,3,4-thiadiazole copper nanoparticles (DMTD-CuNPs) was synthesized by hydrothermal method based on monovalent copper (Cu(I)) and 2,5-dimercapto-1,3,4-thiadiazole (DMTD), and it can effectively detect cysteine (Cys) in plasma. Experiments show that DMTD can reduces band gap of Cu(I) in DMTD-CuNPs, promote charge transfer transition from DMTD to Cu(I) and significantly enhance fluorescence intensity of DMTD-CuNPs at 515 nm. The large Stokes shift of DMTD-CuNPs is 315 nm, which can reduce the self-quenching of probe fluorescence and improves detection accuracy of the probe. In the presence of Cys, fluorescence of DMTD-CuNPs at 515 nm is significantly quenched because Cys reacts with Cu(I) in DMTD-CuNPs through Cu-S bond to form reduced charge transfer, which can be successfully used for the detection of Cys. Linear range and detection limit for Cys detection are 25-65 µM and 50 nM, respectively. Furthermore, feasibility of detecting Cys in plasma using DMTD-CuNPs probe was evaluated by standard addition method, and the absolute recovery is 96-99%. Such a DMTD-CuNPs probe shows high sensitivity, good selectivity and low detection limit for Cys, which is expected to be used for the practical analysis of Cys in plasma.

Dual Response Site Fluorescent Probe for Highly Sensitive Detection of Cys/Hcy and GSH In Vivo through Two Different Emission Channels

Much research has demonstrated that metabolic imbalances of biothiols are closely associated with the emergence of different types of disease. In view of the significant effect of biothiols, quantitative evaluation and discrimination of intracellular Cys/Hcy and GSH in complex biological environments is very important. In this study, probe CDS-NBD, synthesized by attaching 2,4-dinitrobenzenesulfonate (DNBS, site 1) and nitrobenzoxadiazole (NBD, site 2) as the highly sensitive and selective dual response site for thiols onto the coumarin derivative 7-hydroxycoumarin-4-acetic acid, exhibited large separation of the emission wavelengths, fast response, notable fluorescence enhancement, excellent sensitivity and selectivity to Cys/Hcy and GSH over other biological species. Additionally, CDS-NBD could make a distinction between two different fluorescent signals, GSH (an obvious blue fluorescence) and Cys/Hcy (a mixed blue-green fluorescence). Further study on imaging of Cys/Hcy and GSH in vivo by employing probe CDS-NBD could also be successfully achieved.

Coumarin-based fluorescent probe with 4-phenylselenium as the active site for multi-channel discrimination of biothiols

Biological mercaptans, also known as biothiols, play their own roles in a number of important physiological processes, and the abnormal levels of biothiols are closely associated with a variety of...

Prevent or Cure-The Unprecedented Need for Self-Reporting Materials

Self-reporting smart materials are highly relevant in modern soft matter materials science, as they allow for the autonomous detection of changes in synthetic polymers, materials, and composites. Despite critical advantages of such materials, for example, prolonged lifetime or prevention of disastrous material failures, they have gained much less attention than self-healing materials. However, as diagnosis is critical for any therapy, it is of the utmost importance to report the existence of system changes and their exact location to prevent them from spreading. Thus, we herein critically review the chemistry of self-reporting soft matter materials systems and highlight how current challenges and limitations may be overcome by successfully transferring self-reporting research concepts from the laboratory to the real world. Especially in the space of diagnostic self-reporting systems, the recent SARS-CoV-2 (COVID-19) pandemic indicates an urgent need for such concepts that may be able to detect the presence of viruses or bacteria on and within materials in a self-reporting fashion.

Development of a NIR fluorescent probe for highly selective and sensitive detection of cysteine in living cells and in vivo

Cysteine (Cys) plays important physiological roles in the human body, and abnormal Cys concentrations can cause a variety of diseases. Thus, detecting Cys with high selectivity and sensitivity in vivo is important. Near-infrared (NIR) fluorescent probes are widely employed in biological detection because of their excellent optical properties such as minimal damage to biological samples, low background interference and high signal-to-noise ratio. However, few NIR fluorescent probes that can detect Cys over homocysteine (Hcy) and glutathione (GSH) have been reported because of their similar reactivity and structure. In this work, a highly water-soluble NIR probe (CYNA) for detecting Cys whose structure is similar to that of indocyanine green and is based on cyanine skeleton was synthesized and via aromatic nucleophilic substitution-rearrangement (SNAr-rearrangement) to specific recognize the cysteine. The probe showed high selectivity toward Cys and superior biosecurity, excellent biocompatibility and prolonged dynamic imaging. It also has long fluorescence emission wavelength (820 nm), low detection limit (14 nM) and was successfully applied for visualizing Cys in living cells and mice, which has great promise for applications in noninvasive vivo biological imaging and detection.