Near-IR discriminative detection of H2S and Cysteine with 7-nitro-2,1,3-benzoxadiazole-perylenediimide conjugate in water, live cells and solid state: Mimicking IMP, INH and NOR/OR complimentary logic

Activity-Based Fluorescent Probes for Hydrogen Sulfide and Related Reactive Sulfur Species

Hydrogen sulfide (H2S) is not only a well-established toxic gas but also an important small molecule bioregulator in all kingdoms of life. In contemporary biology, H2S is often classified as a "gasotransmitter," meaning that it is an endogenously produced membrane permeable gas that carries out essential cellular processes. Fluorescent probes for H2S and related reactive sulfur species (RSS) detection provide an important cornerstone for investigating the multifaceted roles of these important small molecules in complex biological systems. A now common approach to develop such tools is to develop "activity-based probes" that couple a specific H2S-mediated chemical reaction to a fluorescent output. This Review covers the different types of such probes and also highlights the chemical mechanisms by which each probe type is activated by specific RSS. Common examples include reduction of oxidized nitrogen motifs, disulfide exchange, electrophilic reactions, metal precipitation, and metal coordination. In addition, we also outline complementary activity-based probes for imaging reductant-labile and sulfane sulfur species, including persulfides and polysulfides. For probes highlighted in this Review, we focus on small molecule systems with demonstrated compatibility in cellular systems or related applications. Building from breadth of reported activity-based strategies and application, we also highlight key unmet challenges and future opportunities for advancing activity-based probes for H2S and related RSS.

Perylene diimide-based radical anions for the rapid detection of picomolar H2O2 in an aqueous medium

The formation of radical anions (PDI 1˙-) using H2S as a sacrificial electron donor in 50% HEPES buffer-THF solution is reported. PDI 1˙- was confirmed by optical, I-V plot, CV, DPV, NOBF4 and EPR studies. PDI 1˙- has a half-life of 96 minutes in solution and 11 days in the solid state without any additive. The formation of PDI 1˙- was confirmed by AFM and SEM. PDI 1˙- can be used for the detection of 26.6 pM of H2O2 supported by optical and CV data.

A highly selective colorimetric and fluorescent probe Eu(tdl)2abp for H2S sensing: Application in live cell imaging and natural water

Using 4-([2,2': 6', 2'- terpyridin] -4'-yl) -N, N-dimethylaniline (tdl) as auxiliary ligand and 6-azido-2,2'-bipyridine (abp) as recognition ligand, a europium complex fluorescent probe Eu(4-([2,2': 6', 2'-terpyridin] -4' -yl) -N, N-dimethylaniline)₂-6-azido-2,2'-bipyridine Eu(tdl)₂abp for efficient and specific recognition of hydrogen sulfide (H₂S) was successfully synthesized and characterized by NMR and MS. Eu(tdl)₂abp represented "on-off" fluorescence signals for H₂S and its color changes could be identified with naked eyes. Eu(tdl)₂abp had short response time (2 min) to H₂S, high selectivity and good anti-interference, large stokes shift (207 nm). In various samples, when H₂S existed, the azide group was reduced to amine group, resulting in closed fluorescence signal, and the fluorescence intensity reached the degree of quenching without being affected by other interference. At the same time, there was a good linear relationship between relative fluorescence intensity and H₂S concentration with the detection limit (LOD) of 0.64 μM. The sensing mechanism of Eu(tdl)₂abp to detect H₂S was characterized by ¹H NMR and HR-MS. Eu(tdl)₂abp was used with success for the sensitive detection of H₂S in natural water and living cells.

Rapid detection of hydrogen sulfide in vegetables and monosodium glutamate based on perylene supramolecular aggregates using an indicator displacement assays strategy

Hydrogen sulfide (H₂S) has been clearly identified as a hazardous chemical pollutant that seriously affects food safety and human health. In order to develop a rapid, accurate and efficient H₂S tracking method, this work propose a strategy based on indicator displacement assays (IDA). A water-soluble histidine-modified perylene diimide fluorescent probe was synthesized by a one-step method, and the probe can form supramolecular aggregates in the presence of Cd²⁺. There will be a fluorescence transformation of probe, caused by the change of the state of aggregation and adjusted by various concentration of S^2-, which can achieve the fluorescence detection of S^2-. The limit of detection is as low as 0.41 µmol/L. Particularly worth mentioning is that the probe in this work can be recycled for at least 5 times, which is environmentally friendly and economical. Finally, this method was applied in three kinds of vegetables and monosodium glutamate samples.

Ratiometric fluorescence sensing with logical operation: Theory, design and applications

The construction of ratiometric fluorescence sensing logic systems has gradually become a hot topic in fluorescence analysis, due to the multi-target analysis potential of logic operations and the high specificity and selectivity of ratiometric fluorescence sensing. In this paper, the basic principles of various logic functions implemented in ratiometric fluorescence detection are discussed in the context of sensing mechanisms, and the strategies for constructing logic systems in different ratiometric fluorescence sensing application areas are summarized. Although there are limitations such as cumbersome operations and complicated experiments, ratiometric fluorescence sensing logic circuits that combine the visualization of logic operations and the accuracy of ratiometric fluorescence are still worthy of in-depth study. This review may be useful for researchers interested in the construction of logic operations based on ratiometric fluorescence sensing applications.

Synthesis, self-assembly and biolabeling of perylene diimide-tyrosine alkyl amide based amphiphiles: nanomolar detection of AOT surfactant

Perylene diimide-tyrosine alkyl amide based amphiphiles were synthesized and characterized. PDI 3a showed ‘beehive’ nanostructure and applied for biolabeling of MG-63 live cells. PDI 3b can be used for NIR detection of anionic surfactant.

NBD-based synthetic probes for sensing small molecules and proteins: design, sensing mechanisms and biological applications

Compounds with a nitrobenzoxadiazole (NBD) skeleton exhibit prominent useful properties including environmental sensitivity, high reactivity toward amines and biothiols (including H2S) accompanied by distinct colorimetric and fluorescent changes, fluorescence-quenching ability, and small size, all of which facilitate biomolecular sensing and self-assembly. Amines are important biological nucleophiles, and the unique activity of NBD ethers with amines has allowed for site-specific protein labelling and for the detection of enzyme activities. Both H2S and biothiols are involved in a wide range of physiological processes in mammals, and misregulation of these small molecules is associated with numerous diseases including cancers. In this review, we focus on NBD-based synthetic probes as advanced chemical tools for biomolecular sensing. Specifically, we discuss the sensing mechanisms and selectivity of the probes, the design strategies for multi-reactable multi-quenching probes, and the associated biological applications of these important constructs. We also highlight self-assembled NBD-based probes and outline future directions for NBD-based chemosensors. We hope that this comprehensive review will facilitate the development of future probes for investigating and understanding different biological processes and aid the development of potential theranostic agents.

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.

A novel rosamine-based fluorescent probe for the rapid and selective detection of cysteine in BSA, water, milk, cabbage, radish, apple, and pear

A novel fluorescent probe (RA), based on the rosamine skeleton bearing acrylate group, has been reasonably designed and prepared, which employed an addition-cyclization-elimination sequence reaction mechanism to detect cysteine. RA displayed rapid response to cysteine within 1.5 min, and exhibited satisfactory selectivity for cysteine over H₂S, glutathione (Glu), and homocysteine (Hcy), due to the formation of seven-membered lactam favored kinetically. Fluorescence ratio was utilized to detect cysteine from 6.0 to 20.0 μM with a detection limit of 0.29 μM. More, RA was used to monitor cysteine in BSA, water, milk, milk powder, cabbage, radish, apple, and pear.

Cost-effective diagnostic kits for selective detection of gaseous H2S

Unsymmetrical tri-functionalized perylene diimide dyes were explored for making solution- and solid-state-based colorimetric kits for the detection of gaseous and aqueous H2S.

Perylene diimides: will they flourish as reaction-based probes?

Perylene diimides (PDI) are a well-studied class of functional organic dyes, and in recent years, they have been accepted as promising scaffolds for the design of small molecule/polymer-based chromogenic and fluorogenic reaction-based-probes because of their strong absorption combined with high fluorescence quantum yield in organic solvents, low reduction potential, good electron-acceptor properties, and broad color range properties. Undoubtedly, the intrinsically poor solubility of PDI-based derivatives in water greatly hampers their exploitation as reaction-based probes; however, a vast array of functionalizations now offer design strategies that have resulted in >50% solubility of PDI derivatives in water. A chemodosimeter, wherein chemical transformation is achieved by specific reactions, affords naked-eye visibility, fast response time, sensitivity, ratiometric response, and low cost. The present review focuses on the progress of PDI-based chemodosimeters achieved so far since the inception of this member in the rylene diimide family. This comprehensive review may facilitate the development of more powerful chemodosimeters based on PDI for broad and exciting applications in the future.

Near-IR oxime-based solvatochromic perylene diimide probe as a chemosensor for Pd species and Cu2+ ions in water and live cells

A near-IR perylene diimide probe (OPR-PDI) containing an oxime-propargyl hybrid moiety at the bay position, was designed and synthesized for detection of Pd species and Cu²⁺ ions in 90% water, the solid state and MG-63 live cells. The aggregation tendency of OPR-PDI in different polarity solvents transmits solvatochromic and fluorochromic properties to differentiate certain organic solvents. Supramolecular aggregates of OPR-PDI in 90% water act as a dual chemosensor for palladium (Pd) species via de-propargylation or hydrolysis of the Schiff-base and Cu²⁺ ions via complexation with the O/N binding site with a low limit of detection (LOD) of the order of 7.9 × 10^-8 M and 3.4 × 10^-7 M respectively. TLC strips coated with OPR-PDI can be applied for sensing of Pd⁰ and Cu²⁺ ions in the solid state at levels as low as 34.6 ng cm^-2 and 10.5 ng cm^-2. OPR-PDI imprinted TLC strips could be used as paper sheets for writing coloured alphabets using Pd⁰ and Cu²⁺ ions as ink. Moreover, MTT assay showed that OPR-PDI has very low cytotoxicity (IC₅₀ = 230 μM), good permeability, biocompatibility and can be applied for bio-imaging of Pd species and Cu²⁺ ions in MG-63 cells. DFT calculations, and cyclic voltammetric (CV) and NMR titration studies have also been discussed.

Self-assembled nanofibers of perylene diimide for the detection of hypochlorite in water, bio-fluids and solid-state: exogenous and endogenous bioimaging of hypochlorite in cells

PDI–DAMN shows the disintegration of nanofibers into flake-like aggregates with ‘turn-on’ fluorescence response on the addition of ClO⁻ in solid-state, bio-fluids and MG-63 cells.