Synthesis and Applications of Fluorescent Chemosensors: A Review

Fluorescent sensors have emerged as powerful tools in analytical chemistry for the detection and quantification of heavy and transition metal ions in aqueous samples. These metal ions pollute the environment and cause a number of diseases, such as irritability, anaemia, muscle paralysis, neurological damage, and memory loss. Moreover, we explore the wide spectrum of applications in environmental monitoring, where these sensors enable precise detection of contaminants, as well as in biomedical fields, facilitating diagnostic and therapeutic advancements. While highlighting the exceptional progress achieved in this field, I also address the challenges and future prospects for the continued development of fluorescent sensors, emphasizing their potential to shape the future of water quality assessment and analytical chemistry. Heavy and transition metals are of great concern because of their extreme toxicity even at very low concentration and tendency to be accumulated in bodies of living organisms. During the recent years, the design and synthesis of fluorescent chemosensors for sensing environmentally and biologically relevant important metals, particularly for heavy and transition metals, is of great interest. Opon complexation with heavy and transition metals, the fluorescence intensity of these fluorescent chemosensors either quenched or enhanced. The current review paper explains various fluorescent chemosensors for determination of toxic heavy and transition metals in environmental water samples.

Trefoil-Shaped Metal-Organic Cages as Fluorescent Chemosensors for Multiple Detection of Fe3+, Cr2O72-, and Antibiotics

The construction of metal-organic cages (MOCs) with specific structures and fluorescence sensing properties is of much importance and challenging. Herein, a novel phenanthroline-based metal-organic cage, [Cd₃L₃·6MeOH·6H₂O] (1), was synthesized by metal-directed assembly of the ligand 3,3'-[(1E,1'E)-(1,10-phenanthroline-2,9-diyl)bis(ethene-2,1-diyl)]dibenzoic acid (H₂L) and CdI₂ using a solvothermal method. According to single-crystal X-ray analysis, cage 1 exhibits a rare trefoil-shaped structure. Meanwhile, the discrete MOCs are further stacked into a 3D porous supramolecular structure through abundant intermolecular C-H···O interactions. Additionally, through exploration of fluorescence sensing on cations, anions, and antibiotics in aqueous solution, the experimental results indicate that cage 1 has excellent fluorescence sensing abilities for Fe³⁺, Cr₂O₇^2-, and nitrofuran and nitroimidazole antibiotics. The sensing ability of 1 remains unaltered for five cycles toward all analytes. The above results suggested that cage 1 can be considered a potential multiple sensor for the detection of Fe³⁺, Cr₂O₇^2-, and some antibiotics.

Cu(I)-Catalyzed Click Chemistry in Glycoscience and Their Diverse Applications

Copper(I)-catalyzed 1,3-dipolar cycloaddition between organic azides and terminal alkynes, commonly known as CuAAC or click chemistry, has been identified as one of the most successful, versatile, reliable, and modular strategies for the rapid and regioselective construction of 1,4-disubstituted 1,2,3-triazoles as diversely functionalized molecules. Carbohydrates, an integral part of living cells, have several fascinating features, including their structural diversity, biocompatibility, bioavailability, hydrophilicity, and superior ADME properties with minimal toxicity, which support increased demand to explore them as versatile scaffolds for easy access to diverse glycohybrids and well-defined glycoconjugates for complete chemical, biochemical, and pharmacological investigations. This review highlights the successful development of CuAAC or click chemistry in emerging areas of glycoscience, including the synthesis of triazole appended carbohydrate-containing molecular architectures (mainly glycohybrids, glycoconjugates, glycopolymers, glycopeptides, glycoproteins, glycolipids, glycoclusters, and glycodendrimers through regioselective triazole forming modular and bio-orthogonal coupling protocols). It discusses the widespread applications of these glycoproducts as enzyme inhibitors in drug discovery and development, sensing, gelation, chelation, glycosylation, and catalysis. This review also covers the impact of click chemistry and provides future perspectives on its role in various emerging disciplines of science and technology.

Antitumor Activity of Cyclodextrin-based Supramolecular Platinum Prodrug In vitro and In vivo

Background:

Considering the limitations of cisplatin in clinical application, there is ongoing research to fabricate new platinum-containing prodrug which are highly effective to tumor cells and have low toxicity to normal cells.

Methods:

In this study, a cyclodextrin-based supramolecular platinum prodrug that is 6,6’-ophenylenediseleno- bridged bis (β-cyclodextrin)s (CD) and its potassium tetrachloroplatinate(II) complex was reported. The cytotoxicity experiments were performed to evaluate the anticancer activities of supramolecular prodrug in vitro by means of MTT assay. The practical application of supramolecular prodrug in tumor treatment in vivo were evaluated using BALB/c nude mice model bearing Hela cancer cells.

Results:

Compared with commercial anticancer drug cisplatin, the resultant cyclodextrin-based platinum prodrug exhibited comparative anticancer effect but with much lower toxicity side effects in vitro and in vivo.

Conclusion:

The cyclodextrin-based supramolecular platinum prodrug displayed antitumor activity comparable to the commercial antitumor drug cisplatin but with lower side effects both in vitro and in vivo, implying that the two adjacent cyclodextrin cavities not merely act as desired solubilizer, but also endowed the prodrug with cell permeability through the interaction of cyclodextrin with phospholipids and cholesterol on cell membrane.

Recent Advances in Macrocyclic Fluorescent Probes for Ion Sensing

Small-molecule fluorescent probes play a myriad of important roles in chemical sensing. Many such systems incorporating a receptor component designed to recognise and bind a specific analyte, and a reporter or transducer component which signals the binding event with a change in fluorescence output have been developed. Fluorescent probes use a variety of mechanisms to transmit the binding event to the reporter unit, including photoinduced electron transfer (PET), charge transfer (CT), Förster resonance energy transfer (FRET), excimer formation, and aggregation induced emission (AIE) or aggregation caused quenching (ACQ). These systems respond to a wide array of potential analytes including protons, metal cations, anions, carbohydrates, and other biomolecules. This review surveys important new fluorescence-based probes for these and other analytes that have been reported over the past five years, focusing on the most widely exploited macrocyclic recognition components, those based on cyclam, calixarenes, cyclodextrins and crown ethers; other macrocyclic and non-macrocyclic receptors are also discussed.

Simultaneous expression and transportation of insulin by supramolecular polysaccharide nanocluster

Drug/gene transportation systems with stimuli-responsive release behaviors are becoming research hotspots in biochemical and biomedical fields. In this work, a glucose-responsive supramolecular nanocluster was successfully constructed by the intermolecular complexation of phenylboronic acid modified β-cyclodextrin with adamantane modified polyethylenimine, which could be used as a biocompatible carrier for insulin and pCMV3-C-GFPSpark-Ins DNA which could express insulin co-delivery. Benefiting from the response capability of phenylboronic acid moiety toward glucose, the encapsulated insulin could be specifically released and the corresponding targeted DNA could efficiently express insulin in HepG2 cell, accompanied by the high-level insulin release in vitro. Our results demonstrate that the simultaneous insulin drug delivery and insulin gene transfection in a controlled mode may have great potential in the clinical diabetes treatments.

Polysaccharide-based Noncovalent Assembly for Targeted Delivery of Taxol

The construction of synthetic straightforward, biocompatible and biodegradable targeted drug delivery system with fluorescent tracking abilities, high anticancer activities and low side effects is still a challenge in the field of biochemistry and material chemistry. In this work, we constructed targeted paclitaxel (Taxol) delivery nanoparticles composed of permethyl-β-cyclodextrin modified hyaluronic acid (HApCD) and porphyrin modified paclitaxel prodrug (PorTaxol), through host-guest and amphiphilic interactions. The obtained nanoparticles (HATXP) were biocompatible and enzymatic biodegradable due to their hydrophilic hyaluronic acid (HA) shell and hydrophobic Taxol core, and exhibited specific targeting internalization into cancer cells via HA receptor mediated endocytosis effects. The cytotoxicity experiments showed that the HATXP exhibited similar anticancer activities to, but much lower side effects than commercial anticancer drug Taxol. The present work would provide a platform for targeted paclitaxel drug delivery and a general protocol for the design of advanced multifunctional nanoscale biomaterials for targeted drug/gene delivery.

A novel supramolecular system with multiple fluorescent states constructed by orthogonal self-assembly

A novel supramolecular fluorescent system was successfully constructed by orthogonal self-assembly of host–guest and metal–ligand interactions. By controlling the non-covalent interactions in different ways, the system exhibits diverse fluorescent switching phenomena.

Recent advances in 1,10-phenanthroline ligands for chemosensing of cations and anions

This review encompasses and highlights recent developments of 1,10-phenanthroline ligands behaving as a customized moiety used in recognition and sensing of cations and anions.

Recent advances in the construction of fluorescent metallocycles and metallocages via coordination-driven self-assembly

During the last few years, the construction of fluorescent metallocycles and metallocages has attracted considerable attention because of their wide applications in fluorescence detection of metal ions, anions, or small molecules, mimicking complicated natural photo-processes, and preparing photoelectric devices, etc. This perspective focuses on the recent advances in the construction of a variety of fluorescent metallocycles and metallocages via coordination-driven self-assembly. In addition, the fluorescence properties and the applications of these organometallic architectures have also been discussed.

Room-temperature phosphorescence by Mn-doped ZnS quantum dots hybrid with Fenton system for the selective detection of Fe2+

Fe²⁺ was selectively detected based on the phosphorescence quenching of MPA–Mn : ZnS QDs caused by hydroxyl radicals from the Fenton reaction.

Click synthesis of a novel triazole bridged AIE active cyclodextrin probe for specific detection of Cd2+

A novel aggregation induced emission (AIE) active cyclodextrin (CD) was synthesized via click chemistry, which is the first reported clicked AIE probe for the specific detection of Cd²⁺.

Recycling gene carrier with high efficiency and low toxicity mediated by L-cystine-bridged bis(β-cyclodextrin)s

Constructing safe and effective gene delivery carriers is becoming highly desirable for gene therapy. Herein, a series of supramolecular crosslinking system were prepared through host-guest binding of adamantyl-modified low molecular weight of polyethyleneimine with L-cystine-bridged bis(β-cyclodextrin)s and characterized by ¹H NMR titration, electron microscopy, zeta potential, dynamic light-scattering, gel electrophoresis, flow cytometry and confocal fluorescence microscopy. The results showed that these nanometersized supramolecular crosslinking systems exhibited higher DNA transfection efficiencies and lower cytotoxicity than the commercial DNA carrier gold standard (25 kDa bPEI) for both normal cells and cancer cells, giving a very high DNA transfection efficiency up to 54% for 293T cells. Significantly, this type of supramolecular crosslinking system possesses a number of enzyme-responsive disulfide bonds, which can be cleaved by reductive enzyme to promote the DNA release but recovered by oxidative enzyme to make the carrier renewable. These results demonstrate that these supramolecular crosslinking systems can be used as promising gene carriers.