Synthesis and characterization of cyclophane: The highly selective recognition of Fe3+ in aqueous solution and H2PO4− in acetonitrile solution

Shining a light on liver health: advancements in fluorescence-enhanced enzyme biosensors for early disease detection

Early detection of liver diseases holds paramount importance in optimizing treatment outcomes and prognosis, thereby significantly enhancing the likelihood of recovery while mitigating the risk of progression to liver cancer. Liver diseases encompass a spectrum of conditions, each potentially manifesting distinct enzymatic profiles. Monitoring these enzymes in situ facilitates timely intervention and therapeutic management. In recent years, the field of biosensor technology has witnessed remarkable advancement, owing to strides in biomedicine and computational sciences. Biosensors have garnered widespread utility across medical and biological domains, spanning the detection of disease biomarkers, drug release tracking, ion imaging, and fluorescence imaging within living organisms. These applications have markedly enhanced imaging resolution and have the potential to refine disease diagnosis accuracy for clinicians. A pivotal aspect in the successful application of this technology lies in the construction of fluorescence probes adept at swiftly and selectively identifying target enzymes by amalgamating liver disease enzymes with fluorescence probe technology. However, research in this niche area remains relatively scarce. Building upon this foundational understanding, the present review delineates the utilization of biosensors in the early diagnosis of liver disease. Serving as a theoretical framework, this review envisages the development of high-performance biosensors tailored for the early detection of liver cancer. Furthermore, it offers insights into the potential of biosensor technology to progress and broaden its practical applications, thus contributing to the advancement of diagnostic methodologies in liver disease management.

Highly-ordered assembled organic fluorescent materials for high-resolution bio-sensing: a review

Organic fluorescent materials (OFMs) play a crucial role in the development of biosensors, enabling the extraction of biochemical information within cells and organisms, extending to the human body. Concurrently, OFM biosensors contribute significantly to the progress of modern medical and biological research. However, the practical applications of OFM biosensors face challenges, including issues related to low resolution, dispersivity, and stability. To overcome these challenges, scientists have introduced interactive elements to enhance the order of OFMs. Highly-ordered assembled OFMs represent a novel material type applied to biosensors. In comparison to conventional fluorescent materials, highly-ordered assembled OFMs typically exhibit robust anti-diffusion properties, high imaging contrast, and excellent stability. This approach has emerged as a promising method for effectively tracking bio-signals, particularly in the non-invasive monitoring of chronic diseases. This review introduces several highly-ordered assembled OFMs used in biosensors and also discusses various interactions that are responsible for their assembly, such as hydrogen bonding, π-π interaction, dipole-dipole interaction, and ion electrostatic interaction. Furthermore, it delves into the various applications of these biosensors while addressing the drawbacks that currently limit their commercial application. This review aims to provide a theoretical foundation for designing high-performance, highly-ordered assembled OFM biosensors suitable for practical applications. Additionally, it sheds light on the evolving trends in OFM biosensors and their application fields, offering valuable insights into the future of this dynamic research area.

Fluorescent cyclophanes and their applications

With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host-guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes-in particular, fluorescent cyclophanes, having rich structural characteristics and functions-have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host-guest chemistry and applications related to their structure and properties are highlighted.

An Acylhydrazone-Based Fluorescent Sensor for Sequential Recognition of Al3+ and H2PO4. MATERIALS (BASEL, SWITZERLAND) 2021;14:6392. [PMID: 34771920 PMCID: PMC8585233 DOI: 10.3390/ma14216392]

A novel acylhydrazone-based fluorescent sensor NATB was designed and synthesized for consecutive sensing of Al3+ and H2PO4-. NATB displayed fluorometric sensing to Al3+ and could sequentially detect H2PO4- by fluorescence quenching. The limits of detection for Al3+ and H2PO4- were determined to be 0.83 and 1.7 μM, respectively. The binding ratios of NATB to Al3+ and NATB-Al3+ to H2PO4- were found to be 1:1. The sequential recognition of Al3+ and H2PO4- by NATB could be repeated consecutively. In addition, the practicality of NATB was confirmed with the application of test strips. The sensing mechanisms of Al3+ and H2PO4- by NATB were investigated through fluorescence and UV-Visible spectroscopy, Job plot, ESI-MS, 1H NMR titration, and DFT calculations.

Acridino-Diaza-20-Crown-6 Ethers: New Macrocyclic Hosts for Optochemical Metal Ion Sensing

Acridino-diaza-20-crown-6 ether derivatives as new turn-on type fluorescent chemosensors with an excellent functionality and photophysical properties have been designed and synthesized for metal ion-selective optochemical sensing applications. Spectroscopic studies revealed that in an acetonitrile-based semi-aqueous medium, the sensor molecules exhibited a remarkable fluorescence enhancement with high sensitivity only toward Zn2+, Al3+ and Bi3+, among 23 different metal ions. Studies on complexation showed a great coordinating ability of logK > 4.7 with a 1:1 complex stoichiometry in each case. The detection limits were found to be from 59 nM to micromoles. The new ionophores enabled an optical response without being affected either by the pH in the range of 5.5-7.5, or the presence of various anions or competing metal ions. Varying the N-substituents of the new host-backbone provides diverse opportunities in both immobilization and practical applications without influencing the molecular recognition abilities.

Comparison in practical applications of crown ether sensor molecules containing an acridone or an acridine unit – a study on protonation and complex formation

Crown ethers containing an acridone or an acridine unit are successfully applied opto- and electrochemical cation sensors. The heteroaromatic unit of these macrocycles can be in different forms during the applications, which have a strong influence on the sensing behavior. Moreover, in the case of acridono-macrocycles a prototropic equilibrium takes place upon complexation, which is effected by the physicochemical characteristics. A Pb2+-selective acridono-18-crown-6 ether and its 9-phenylacridino-analogue were used as model compounds for comparing the different forms of the heterocyclic units of these sensor molecules. Since in most practical sensor applications of the fluorescent hosts a non-neutral aqueous medium is present, studies on complexation and signaling were carried out from the aspect of the relationship among protonation, coordinating ability, complex stability and tautomeric equilibrium. A strong interdependence among these factors was found and limitations of using unsubstituted acridino- and acridono-sensor molecules in comparison with their 9-substituted-acridino-analogues were discussed. This study will hopefully serve as a useful standpoint for future development of ionophore-based sensors containing an acridone or an acridine unit.

Thiophene-phenylquinazoline probe for selective ratiometric fluorescence and visual detection of Fe(iii) and turn-off fluorescence for I- and its applications

A 2,5-bis(4-phenylquinazolin-2-yl)thiophene (BQT) probe is designed, synthesized and explored for selective ratiometric fluorescence and visual detection of Fe³⁺ and as a turn-off fluorescence probe for I^- anion. BQT is colorless and has blue emission in CH₃CN solution. BQT selectively complexes with Fe³⁺, turns its solution from colorless to greenish yellow and enables the ratiometric sensing of Fe³⁺ with limit of detection (LOD) and limit of quantitation (LOQ) of 2 × 10^-8 M and 6.1 × 10^-8 M, respectively. Binding constant of BQT with Fe³⁺ is found to be 4.1 × 10^-4 M^-1. BQT is also able to sense I^- anion present in aqueous solution by selectively turning colorless to yellow and fluorescence quenching with a LOD of 1.7 × 10^-7 M and LOQ of 5.2 × 10^-7 M. BQT sensing ability is not influenced by the presence of other metal ions and anions in the vicinity. The BQT-Fe³⁺ complex is thoroughly characterized using MALDI-TOF, NMR and Job's plot. A reversibility experiment with EDTA suggests BQT is a reversible fluorescent chemosensor for Fe³⁺ ions. The spectroscopic data of BQT and its complexes are employed to construct a field test kit for qualitative analysis and INHIBIT logic gate.

Revisiting imidazolium receptors for the recognition of anions: highlighted research during 2010-2019

Imidazolium based receptors selectively recognize anions, and have received more and more attention. In 2006 and 2010, we reviewed the mechanism and progress of imidazolium salt recognition of anions, respectively. In the past ten years, new developments have emerged in this area, including some new imidazolium motifs and the identification of a wider variety of biological anions. In this review, we discuss the progress of imidazolium receptors for the recognition of anions in the period of 2010-2019 and highlight the trends in this area. We first classify receptors based on motifs, including some newly emerging receptors, as well as new advances in existing receptor types at this stage. Then we discuss separately according to the types of anions, including ATP, GTP, DNA and RNA.

New ferrocene-triazole derivatives for multisignaling detection of Cu2+ in aqueous medium and their antibacterial activity

Ferrocene-based naphthalene or quinoline receptors 1-4 linked by triazole were designed and synthesized. Their recognition properties of metal cations have been investigated systematically in aqueous environment. Upon addition 1 equiv. of Cu²⁺ ion, receptors 1 (C₂₃H₁₉FeN₃O) and 2 (C₂₂H₁₈FeN₄O) showed fluorescent turn-off, enhanced absorption and color variations. At the same time, receptor 1 also caused the perturbation of redox potential after addition 1 equiv. of Cu²⁺ ion. Therefore, receptors 1 and 2 behaved as naked-eye chemosensors and fluorescent probes for Cu²⁺ without interference by other ions and with low detection limit. In addition, receptor 1 could also be considered electrochemical sensor for Cu²⁺ having excellent sensitivity and selectivity. However, increasing the molecules flexibility resulted in the lower selectivity of ion recognition in the case of receptors 3 (C₂₄H₂₁FeN₃O) and 4 (C₂₃H₂₀FeN₄O). Furthermore, this series of compounds were nontoxicity and receptor 1 exhibited certain antibacterial activity.

Potential chiral fluorescent molecular probes based on an α,β-unsaturated ketone for anion detection

A series of potential chiral compounds containing an α,β-unsaturated ketone was developed for anion detection. The interplay of compounds and biological momentous anions (Cl⁻, H₂PO₄⁻, I⁻, AcO⁻, HS⁻, F⁻, and Br⁻) was evaluated by UV-vis experiments, fluorescence experiments, and electrochemical tests. By comparison, compound 1 had the best selectivity and compound 5 had the strongest binding ability among the five compounds. And compound 5 had the highest sensitivity to H₂PO₄⁻ among the measured anions, and it also can be applied to actual samples, the content of H₂PO₄⁻ tested in the potassium dihydrogen phosphate fertilizer solution reached above 97.5% of the marked content, and the recovery rates were within the range of 98.5–99.1%, attesting that this method was reliable for the test of H₂PO₄⁻ in fertilizer. Through HRMS titration, circular dichroism and optical rotation experiments, the probable interacted mechanism was proved that the interaction site was the C=C of the α,β-unsaturated ketone structure. In addition, the interacted mechanism was researched from the perspective of chirality. Furthermore, theoretical investigation analysis was introduced to reveal that the roles of molecular frontier orbitals in molecular interplay were determined. Therefore, this series of potential chiral compounds has potential application prospects in anion recognition.

Design and synthesis of a new class of 2,4-thiazolidinedione based macrocycles suitable for Fe3+sensing

Three 2,4-thiazolidinedione based macrocycles, which are very good Fe³⁺sensors in aqueous-ethanol medium, have been synthesized. X-ray crystallography, DFT calculations and MEP analysis have been used for their structural confirmation and for understanding their behavior towards Fe³⁺.