A Fluorescent Probe for Selective Facile Detection of H2S in Serum Based on an Albumin-Binding Fluorophore and Effective Masking Reagent

Influence of atomic electronegativity on ESIPT behaviour for the BTDI and its derivatives: Theoretical exploration

In this work, we theoretically explored the influence of atomic electronegativity on excited-state intramolecular proton transfer (ESIPT) behavior among novel fluorescent probes BTDI and its derivatives (BODI and BSeDI). A thorough examination of the optimized structural parameters and infrared vibrational spectra reveals an enhancement in intramolecular hydrogen bonding within BTDI and its derivatives upon light excitation. This finding is further reinforced by topological analysis and interaction region indicator scatter plots, which underscores the sensitivity of atomic electronegativity to variations in hydrogen bonding strength. With regards to absorption and fluorescence spectra, the decrease in atomic electronegativity leads to a pronounced redshift, primarily attributed to the narrowing of the energy gap. Additionally, an analysis of potential energy curves and the exploration of intrinsic reaction coordinate paths based on transition state structures afford a deeper understanding of the mechanism underlying ESIPT and being modulated through the manipulation of atomic electronegativity. We anticipate that this work on atomic electronegativity regulating ESIPT behavior will serve as a catalyst for novel fluorescent probes in the future, offering fresh perspectives and insights.

Rapid Detection of Bacterial Resistance to β-Lactam Antibiotics with a Relay-Response Chemiluminescence Assay

Bacterial resistance caused by β-lactamases has been a major threat to public health around the world, seriously weakening the efficacy of β-lactam antibiotics, the most widely used therapeutic agents against infectious diseases. To detect the bacterial resistance to β-lactam antibiotics, particularly specific type of β-lactam antibiotics, in a rapid manner, we report herein a relay-response chemiluminescence assay. This assay mainly consists of two reagents: a β-lactam-caged thiophenol and a thiophenol-sensitive chemiluminescence reporter, both of which are synthetically feasible. The selective hydrolysis of β-lactam by β-lactamase leads to the releasing of free thiophenol, which then triggers the emission of a chemiluminescence signal in a relay manner. Three thiophenol-caged β-lactams, structural analogues of cephalothin, cefotaxime, and meropenem, respectively, have been synthesized. And the application of this assay with these analogues of β-lactam antibiotics allows fast detection of β-lactamase-expressing resistant bacteria and, more impressively, provides detailed information on the resistant scope of bacteria.

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.

Small Molecule Optical Probes for Detection of H2S in Water Samples: A Review

Hydrogen sulfide (H2S) is closely linked to not only environmental hazards, but also it affects human health due to its toxic nature and the exposure risks associated with several occupational settings. Therefore, detection of this pollutant in water sources has garnered immense importance in the analytical research arena. Several research groups have devoted great efforts to explore the selective as well as sensitive methods to detect H2S concentrations in water. Recent studies describe different strategies for sensing this ubiquitous gas in real-life water samples. Though many of the designed and developed H2S detection approaches based on the use of organic small molecules facilitate qualitative/quantitative detection of the toxic contaminant in water, optical detection has been acknowledged as one of the best, attributed to the simple, highly sensitive, selective, and good repeatability features of the technique. Therefore, this review is an attempt to offer a general perspective of easy-to-use and fast response optical detection techniques for H2S, fluorimetry and colorimetry, over a wide variety of other instrumental platforms. The review affords a concise summary of the various design strategies adopted by various researchers in constructing small organic molecules as H2S sensors and offers insight into their mechanistic pathways. Moreover, it collates the salient aspects of optical detection techniques and highlights the future scope for prospective exploration in this field based on the limitations of the existing H2S probes.

Serum-Based Detection of Liver Pathology Using a Fluorogenic Alkaline Phosphatase Probe

Development of "ultrahigh contrast" fluorogenic probes for trapping alkaline phosphatase (ALP) activities in human serum is highly desirable for clinical auxiliary diagnosis for hepatobiliary diseases. However, the intrinsic dilemma of incomplete ionization of intramolecular charge transfer (ICT)-based ALP fluorophores and autofluorescence interference of serum result in low sensitivity and accuracy. Given that unique halogen effects could lead to a drastic decrease in the pKa value and a significant enhancement in the fluorescence quantum yield, herein we report an enzyme-activatable near-infrared probe based on a difluoro-substituted dicyanomethylene-4H-chromenep for achieving fluorescent quantification of human serum ALP. Rational design strategy is demonstrated by altering the substituted halogen groups to well regulate the pKa for meeting the physiological precondition. Owing to the complete ionization at pH 7.4 with tremendous fluorescence enhancement, the difluoro-substituted DCM-2F-HP manifests a linear relationship between the emission intensity and ALP concentration in both solution and serum samples. Along with measuring 77 human serum samples, the DCM-2F-HP based fluorescence method not only exhibits significant correlations with clinical colorimetry, but also distinguishes ALP patients from healthy volunteers, as well as assessing the progress of liver disease, thus providing a potential toolbox for quantitatively detecting ALP and warning the stage of hepatopathy.

Gold(I)-Catalyzed Intramolecular Hydrothiophenylation of N-Thiophen-3-yl Alkynylamides for Accessing Thieno[3,2-b]pyridine-5(4H)-ones: Development of F-Actin Specific Fluorescent Probes

Herein, we describe an original synthetic method for a series of fluorescent thieno[3,2-b]pyridine-5(4H)-one derivatives prepared via the gold(I)-catalyzed 6-endo-dig intramolecular hydrothiophenylation process involving N-thiophen-3-yl alkynylamides. The brightness was improved; emission could be tuned, and larger Stokes shifts were recorded. We also designed and synthesized the phalloidin-based fluorescent chemical probes KF-P1 and KF-P2 to realize fluorescent F-actin imaging.

Progress on the reaction-based methods for detection of endogenous hydrogen sulfide

Hydrogen sulfide (H₂S) is a biologically signaling molecule that mediates a wide range of physiological functions, which is frequently misregulated in numerous pathological processes. As such, measurement of H₂S holds great attention due to its unique physiological and pathophysiological roles. Currently, a variety of methods based on the H₂S-involved reactions have been reported for detection of endogenous H₂S, bearing the advantages of good specificity and high sensitivity. This review describes in detail the types of reactions, their mechanisms, and their applications in biological research, thus hopefully providing some guidelines to the researchers in this field for further investigation.

A Highly Selective and Sensitive Colorimetric Chemosensor for the Detection of Hydrogen Sulfide: Real-time Applications in Multiple Platforms

Calorimetric chemosensors are found to be advantageous sensing systems due to their simplicity and favorable responsive properties. Although some colorimetric probes have been reported to detect hydrogen sulfide (H₂ S), the creation of rapid, highly selective, and sensitive probes for the detection of H₂ S remains a challenging target. In this work, we established dinitrosulphonamide decorated phenanthridine, 2,4-dinitro-N-(4-(7,8,13,14-tetrahydrodibenzo[a, i]phenanthridin-5-yl)phenyl)benzenesulfonamide (PHSH), for the calorimetric detection of H₂ S. H₂ S triggered thiolysis of PHSH resulted in a marked absorption enhancement alongside a visual color change from colorless to dark yellow. The result indicated that the chemosensor showed high sensitivity and selectivity with a fast response of less than 10 s with a detection limit as low as 6.5 nM. The chemosensor reaction mechanism with H₂ S was studied by UV-vis, ¹ H NMR, mass and HPLC analysis. In addition, the chemosensor has been used for the determination of H₂ S in many real-time samples.

A ratiometric fluorescence probe for the selective detection of H2S in serum using a pyrene-DPA-Cd2+ complex

A ratiometric and selective hydrogen sulfide (H₂S) detection probe was proposed based on the pyrene-DPA–Cd²⁺ complex through the metal ion displacement approach (MDA) mechanism. While most MDA-based fluorescence probes with paramagnetic Cu²⁺ have focused on the development of a simple turn-on sensor using the broad spectral range of fluorescence enhancement, this ratiometric probe exhibited unchanged monomer emission as a built-in internal reference with an increase in excimer emission with added H₂S. The demonstrated probe showed a rapid response (within 1 min) and a high sensitivity, with 70 nM as the limit of detection. The selectivity for H₂S over cysteine, homocysteine and glutathione was confirmed, and reliable fluorescence enhancement, which could be monitored by the naked eye, was observed upon irradiation with handheld UV light. In addition, this detection system was successfully applied to detect H₂S in human serum without interference from biological molecules.

The pyrene-DPA–Cd²⁺ complex is demonstrated as a ratiometric fluorescence probe for selective hydrogen sulfide detection in serum based on a metal displacement approach.