Imaging Of Biothiols Research Articles

A novel fluorescent probe with large Stokes shift for two-photon imaging of biothiols in living cells, liver tissues and tumor tissues

Cysteine (Cys), homocysteine (Hcy) and glutathione (GSH), the small molecule biological thiols, play essential roles in maintaining human biological systems. Research of quantitative determination of biothiols is always significant. We have designed and synthesized a fluorescent probe ANBI based on a naphthalene-benzo[g]indol-1-ium scaffold, quick respond to biothiols in water. The probe exhibits high stability, high selectivity, good water solubility and biocompatibility. Upon addition of biothiols, notably, probe ANBI showed an intense fluorescence within 5 min and displayed a large Stokes shift of 130 nm (Ex = 460 nm, Em = 590 nm). From the linear relationship of absorbance and intensity vs concentrations of Cys, it was determined that the limits of detection are 2.3 μM and 0.35 μM. Therefore, ANBI can qualitatively and quantitatively detect Cys by spectrometry in biological samples. Successfully, probe ANBI has been applied for biothiols in living HeLa cells by one- and two-photon excitation. Furthermore, we obtain the two-photon excited fluorescence images of ANBI in liver tissues and tumor tissues.

Boron- and nitrogen-doped photoluminescent polymer carbon nanoparticles as nanosensors for imaging detection of Cu2+ and biothiols in living cells

Boron and nitrogen co-doped ellipsoidal polymer carbon nanoparticles-based nanoprobe for fluorescence detection and imaging of biothiols in biological samples.

Redox-Mediated Disassembly to Build Activatable Trimodal Probe for Molecular Imaging of Biothiols.

Activatable multimodal probes that show enhancement of multiplex imaging signals upon interaction with their specific molecular target have become powerful tools for rapid and precise imaging of biological processes. Herein, we report a stimuli-responsive disassembly approach to construct a redox-activatable fluorescence/19F-MRS/1H-MRI triple-functional probe 1. The small molecule probe 1 itself has a high propensity to self-assemble into nanoparticles with quenched fluorescence, attenuated 19F-MRS signal, and high 1H-MRI contrast. Biothiols that are abundant in reducing biological environment were able to cleave the disulfide bond in probe 1 to induce disassembly of the nanoparticles and lead to fluorescence activation (∼70-fold), 19F-MRS signal amplification (∼30-fold) and significant r1 relaxivity reduction (∼68% at 0.5 T). Molecular imaging of reducing environment in live cells and in vivo was realized using probe 1. This approach could facilitate the development of other stimuli-responsive trimodal probes for molecular imaging.

A novel reaction-based fluorescent turn-on probe for biothiols and its application in cell imaging

In this work, a novel fluorescent probe (DOCOU) based on coumarin has been designed and synthesized for the detection of biothiols. In this probe, a new hydroxy-coumarin-based fluorescent dye, HOCOU, was firstly used as the fluorophore and 2, 4-dinitrobenzenesulfonyl (DNBS) group was incorporated as both a recognition unit and a fluorescence quencher. The probe DOCOU shows high selectivity and sensitivity for Cys, Hcy, and GSH over other amino acids and interfering species under physiological conditions. Mechanism study indicated that the remarkable fluorescence turn-on response is induced via a thiolate mediated SNAr reaction. Furthermore, DOCOU features good linearity ranges with low detection limit of 17.1nM for Cys, 14.5nM for GSH, and 40nM for Hcy, respectively. In addition, the probe was successfully applied for imaging biothiols in Hela cells with low cytotoxicity.

A colorimetric and fluorescent probe for detecting intracellular biothiols

A new rapid and highly sensitive coumarin-based probe (probe 1) has been designed and synthesized for detecting intracellular thiols. Probe 1 was prepared by a 4-step procedure as a latent fluorescence probe to achieve high sensitivity and fluorescence turn-on response toward cysteine and homocysteine over GSH and other various natural amino acids under physiological conditions. Owing to specific cyclization between thiols and aldehyde group, probe 1 displayed a highly selectivity toward cysteine and homocysteine. Above all, probe 1 was successfully used for fluorescence imaging of biothiols in Hela cells, and quantitative determination had been achieved within a certain range. Then specific fluorescence imaging of mice organ tissues was obtained for proving the permeability of probe 1. Simultaneously, the viability was measured to be more than 80%, which shows probe 1 can be a rapid and biocompatible probe for biothiols in cells. Furthermore, the measurement of thiols detection in 5 kinds of animal serum showed that probe 1 can be used in determination of biothiols in blood.

Molecular imaging of biothiols and in vitro diagnostics based on an organic chromophore bearing a terbium hybrid probe.

In this research, a novel terbium-based luminescent hybrid inorganic/organic probe was designed and synthesized. Mesoporous silica nanospheres dispersed in water were used as the appropriate host for the covalently linked lanthanide-containing organic structures. The lanthanide structure was linked to a sulfonate ester unit, which, in the presence of biothiols, was cleaved to result in terbium emission. The hybrid probe exhibited the capabilities of quantitative determination and detection limits for biothiols were presented (36.8 nM for Cys, 32.5 nM for GSH, and 34.7 nM for Hcy). Evaluation of luminescence changes in cell culture demonstrated that this smart probe is cell membrane permeable and selectively lights up in the presence of cysteine and glutathione in human embryonic kidney cells and human lung adenocarcinoma cells. This variation in the presence of biothiols can be controlled by the treatment with N-methylmaleimide. The narrow line-like bands and long-lived excited states of this terbium luminescent sensor allows the discrimination of scattering signals and interfering fluorescence derived from biological tissues.

A colorimetric and red emissive fluorescent probe for cysteine and its application in bioimaging

Developing effective methods to detect and image Cys in vivo has become an increasingly important area of research. In this work, two colorimetric and fluorescent sensors 1 and 2 were presented for detecting Cys with different reactive rates in an intramolecular cyclization reaction between acrylate and thiols. Probe 2 is the isomer of the probe 1, which has greater steric hindrance than probe 1. The performed reaction kinetics experiments showed that the reaction rates of 1 with thiols were far more rapid than those of 2 with thiols. From the observed crystal structures of these two compounds, we speculate that the larger steric hindrance around the acrylate group in probe 2 outweighs the electronic effect, thus slowing down the reaction between the acrylate and thiols. Probe 1 was successfully applied with negligible cell toxicity toward the imaging of biothiols in living cells and zebrafish.

Sensing for intracellular thiols by water-insoluble two-photon fluorescent probe incorporating nanogel

A novel “turn-on” two-photon fluorescent probe containing a π-conjugated triarylboron luminogen and a maleimide moiety DMDP-M based on the photo-induced electron transfer (PET) mechanism for biothiol detection was designed and synthesized. By simply loading the hydrophobic DMDP-M on a cross-linked Pluronic® F127 nanogel (CL-F127), a probing system DMDP-M/CL-F127 was established, which shows quick response, high selectivity and sensitivity to cysteine (Cys), homocysteine (Hcy) and glutathione (GSH) in aqueous phase. The DMDP-M/CL-F127 system presented the fastest response to Cys with a rate constant of 0.56min−1, and the detection limit to Cys was calculated to be as low as 0.18μM. The DMDP-M/CL-F127 system has been successfully applied to the fluorescence imaging of biothiols in NIH/3T3 fibroblasts either with single-photon or two-photon excitation because of its high biocompatibility and cell-membrane permeability. The present work provides a general, simple and efficient strategy for the application of hydrophobic molecules to sensing biothiols in aqueous phase, and a novel sensing system for intracellular biothiols fitted for both single-photon and two-photon fluorescence imaging.

A functional ruthenium(ii) complex for imaging biothiols in living bodies.

A unique ruthenium(ii) complex, [Ru(bpy)2(DNS-bpy)](PF6)2 [bpy: 2,2'-bipyridine, DNS-bpy: 4-(2,4-dinitrophenylthio)-2,2'-bipyridine], that can act as a probe for the recognition and luminescence sensing of biothiols has been designed and synthesized. Due to the presence of effective photo-induced electron transfer (PET) from the potent electron donor (Ru-bpy centre) to the strong electron acceptor (2,4-dinitrophenyl moiety), the Ru(ii) complex itself is weakly luminescent. Reaction of [Ru(bpy)2(DNS-bpy)](PF6)2 with biothiols leads to the replacement of the 2,4-dinitrophenyl moiety by biothiols, which results in the loss of PET within the complex, to allow recovery of the MLCT-based emission of the Ru(ii) complex with an 80-fold increase in luminescence intensity. Taking advantage of the high specificity and sensitivity, and the excellent photophysical properties of Ru(ii) complexes, [Ru(bpy)2(DNS-bpy)](PF6)2 was successfully applied to the luminescence imaging of biothiols in living Daphnia magna. The results demonstrated the practical applicability of [Ru(bpy)2(DNS-bpy)](PF6)2 as a luminescent probe for the monitoring of biothiols in living bodies.

An iminocoumarin sulfonamide based turn-on fluorescent probe for the detection of biothiols in aqueous solution.

A new chemodosimeter for the highly selective sensing and imaging of biothiols was designed and realized in phosphate-buffered saline solution at pH 7.4 through a fluorescence "off-on" response. A unique mechanism featuring a two-step cascade (biothiols→H2 O) sequence for this remarkable recognition is disclosed for the first time.

Live-cell imaging of biothiols via thiol/disulfide exchange to trigger the photoinduced electron transfer of gold-nanodot sensor

Biothiols have been reported to involve in intracellular redox-homeostasis against oxidative stress. In this study, a highly selective and sensitive fluorescent probe for sensing biothiols is explored by using an ultrasmall gold nanodot (AuND), the dendrimer-entrapped Au8-cluster. This strategy relies upon a thiol/disulfide exchange to trigger the fluorescence change through a photoinduced electron transfer (PET) process between the Au8-cluster (as an electron donor) and 2-pyridinethiol (2-PyT) (as an electron acceptor) for sensing biothiols. When 2-PyT is released via the cleavage of disulfide bonds by biothiols, the PET process from the Au8-cluster to 2-PyT is initiated, resulting in fluorescence quenching. The fluorescence intensity was found to decrease linearly with glutathione (GSH) concentration (0–1500μM) at physiological relevant levels and the limit of detection for GSH was 15.4μM. Compared to most nanoparticle-based fluorescent probes that are limited to detect low molecular weight thiols (LMWTs; i.e., GSH and cysteine), the ultrasmall Au8-cluster-based probe exhibited less steric hindrance and can be directly applied in selectively and sensitively detecting both LMWTs and high molecular weight thiols (HMWTs; i.e., protein thiols). Based on such sensing platform, the surface-functionalized Au8-cluster has significant promise for use as an efficient nanoprobe for intracellular fluorescence imaging of biothiols including protein thiols in living cells whereas other nanoparticle-based fluorescent probes cannot.

Rational Design of Phosphorescent Chemodosimeter for Reaction‐Based One‐ and Two‐Photon and Time‐Resolved Luminescent Imaging of Biothiols in Living Cells

A selective phosphorescent biothiols probe is synthesized based on Ir(III) complex 1, which has 2,2'-biquinoline as the N^N ligand for realizing the satisfied two-photon absorption cross-section and two-functionalized 2-phenylpyridine ligands with an α,β-unsaturated ketone moiety as the thiol reaction site. The one- and two-photon optical properties of 1 are investigated through UV-vis absorption spectrum and photoluminescence spectrum. This Ir(III) complex can act as an excellent one- and two-photon excited "OFF-ON" phosphorescent probe for biothiols based on the 1,4-addition of biothiol to α,β-unsaturated ketones. Moreover, one- and two-photon-induced luminescent imagings of biothiols in living cells are also realized. Furthermore, the experiments of time-resolved photoluminescence technique and fluorescence lifetime imaging microscopy demonstrate that 1 is able to detect biothiols in the presence of strong background fluorescence. In addition, probe 1 is adsorbed into the shell of mesoporous silica nanoparticles with core-shell structure to form a nanoprobe, which can realize the ratiometric detection of biothiols in absolute water solution and living cells based on two phosphorescent signals.

Two-photon probes based on arylsulfonyl azides: Fluorescence detection and imaging of biothiols

Two-photon probes for biothiols are developed based on arylsulfonyl azides for the first time. Thus, 6-(dimethylamino)naphthalene-2-sulfonyl azide and its triphenylphosphonium derivative undergo a fast reduction with turn-on fluorescence change by typical biothiols such as hydrogen sulfide, glutathione, cysteine, and homocysteine to produce the corresponding sulfonamides that is two-photon excitable. The cationic probe enables the selective imaging of the biothiols in mitochondria by two-photon fluorescence microscopy.

Water-soluble conjugated polymer–Cu(II) system as a turn-on fluorescence probe for label-free detection of glutathione and cysteine in biological fluids

In this paper, a new one-step turn-on sensor was developed for the detection of glutathione (GSH) and cysteine (Cys). The photoluminescence (PL) intensity of the water-soluble fluorescent conjugated polymers PPESO3 could be quenched by Cu(II) due to the strong electrostatic interaction and electron transfer between PPESO3 and Cu2+. In the presence of biothiols, such as GSH and Cys, Cu(II) preferred to react with biothiols to form the Cu(II)S bond due to the strong affinity between Cu(II) and thiols. The recovered PL intensity of PPESO3 was proportional to the concentration of GSH or Cys in the concentration ranges of 1.0×10−7 to 1.5×10−5mol/L and 1.0×10−7 to 2.0×10−5mol/L, respectively. The detection limit for GSH and Cys were 4.0×10−8 and 4.5×10−8mol/L, respectively. The established method shows a high selectivity for biothiols compared with other twelve amino acids without thiols group. Furthermore, the PPESO3–Cu(II) system as a fluorescence probe was successfully used for fluorescence imaging of biothiols in the HepG2 cells, which presents a potential application in bioimaging field.

Fluorescent detection of biothiols based on a novel cascade reaction

A fluorescein-based biothiol probe 1 was exploited based on a novel thiol-specific cascade reaction, which could detect and image biothiols in both aqueous solution and cells with high selectivity, sensitivity and signal-to-noise ratio.