Red and Near-Infrared Fluorescent Probe for Distinguishing Cysteine and Homocysteine through Single-Wavelength Excitation with Distinctly Dual Emissions

Abstract

Small-molecule biothiols, including cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), participate in various pathological and physiological processes. It is still a challenge to simultaneously distinguish Cys and Hcy because of their similar structures and reactivities, as well as the interference from the high intramolecular concentration of GSH. Herein, a novel fluorescent probe, CySI, based on cyanine and thioester was developed to differentiate Cys and Hcy through a singlewavelength excitation and two distinctly separated emission channels. The probe exhibited a turn-on fluorescence response to Cys at both 625 nm (the red channel) and 740 nm (the nearinfrared channel) but only showed fluorescence turn-on to Hcy at 740 nm (the near-infrared channel) and no fluorescent response to GSH. With the aid of built-in self-calibration of single excitation and dual emissions, simultaneous discriminative determinations of Cys and Hcy were realized through red and near-infrared channels. CySI exhibited excellent selectivity toward Cys and Hcy with a fast response. This probe was further exploited to visualize exogenous Cys and Hcy in cells through dual emission channels under one excitation. Moreover, it could efficiently target mitochondria and was applied to monitor the endogenous Cys fluctuations independently in mitochondria through the red emission channel.

A ratiometric fluorescent probe based on two-isophorone fluorophore for detecting cysteine

“…Compared with common analysis methods such as fluorescent spectroscopy, potentiometry, and high performance liquid chromatography (HPLC), 9,[12][13][14][15][16][17][18] which are cumbersome and less used for the intracellular detection of biological thiols, fluorescent probes have attracted increasing attention in this field because of their simple operation, high resolution, high sensitivity, real-time detection, penetrability and noninvasiveness. [19][20][21][22][23][24][25][26] At present, more and more small molecule fluorescent probes and nanosensors have been designed, synthesized, and extensively used in the detection of biological thiols. [27][28][29][30][31][32][33][34] So far, numerous fluorescent probes for Cys detection based on various reaction mechanisms have been synthesized and reported, which are mainly based on Michael addition reactions, cleavage of disulfide bonds, substitution reactions, disulfide exchange, etc., 35 and nanosensors are mainly based on the colorimetric reaction of the aggregation of gold nanoparticles, the aggregation of graphene quantum dots and the fluorescence reaction, etc.…”

Homocysteine-specific fluorescence detection and quantification for evaluating S-adenosylhomocysteine hydrolase activity

“…In recent years, fluorescence detection has attracted extensive attention due to its advantages of simplicity, high sensitivity, and excellent temporal-spatial resolution. 14–25 Most of the designed strategies of fluorescent probes for biothiols predominantly employ strong nucleophilicity of the sulfydryl group, and the reactions include cyclization, Michael addition, cleavage reaction, nucleophilic substitution, and cleavage of S–S bonds. 26–37 Some of these probes themselves are non-fluorescence due to various quenching modes, such as photoinduced electron transfer (PET), fluorescence resonance energy transfer (FRET), and intramolecular charge transfer (ICT), their fluorescence can be switched on by biothiols, thus realizing the detection of fluorescence in biothiols.…”

Just-in-Time Learning-Integrated Partial Least-Squares Strategy for Accurately Predicting 71 Chemical Constituents in Chinese Tobacco by Near-Infrared Spectroscopy

“…Owing to its rapidity, high efficiency, and nondestructivity, near-infrared (NIR) spectroscopy has been used widely in biological, , petrochemical, pharmaceutical, agricultural, − and food-processing , applications. NIR spectroscopy is also effective in the quantitative analysis of tobacco components. ,, Chemical models for components having high contents, such as total sugar (TS), reducing sugar (RS), total nitrogen (TN), nicotine (NIC), and chlorine (Cl), are relatively robust. ,− However, the performance of trace-component models may be subideal. , Furthermore, models of organic acids, amino acids, and Amadori compounds have rarely been reported, although these compounds critically influence the unique style of tobacco.…”

“…4,5 However, traditional quantitative analysis methods, such as chromatographic analysis and continuousflow analysis, are time-consuming and expensive and require complex sample pretreatment procedures. 6,7 Owing to its rapidity, high efficiency, and nondestructivity, near-infrared (NIR) spectroscopy has been used widely in biological, 8,9 petrochemical, 10 pharmaceutical, 11 agricultural, 12−14 and food-processing 15,16 applications. NIR spectroscopy is also effective in the quantitative analysis of tobacco components.…”