A Supramolecular Gel-Based Protocol for the Detection of α-Glycosidases for Screening Potential Drugs.

α-Glycosidases are carbohydrate-digesting enzymes that catalyze the hydrolysis of α-1,4-glycopyranoside bonds from oligosaccharides and disaccharides. α-Glucosidase is an important biomarker for the diagnosis of type-II diabetes, Azoospermia and Pompe diseases. Additionally, the mutations in α-galactosidase lead to Fabry disease.

Paper-based sensing of phytotoxicant gossypol in aqueous media through turn-on visible-light emitting lanthanide-luminescence.

Gossypol, a phytotoxicant in cotton-seed oil, has been found to sensitize Tb(III)-luminescence in a supramolecular hydrogel. Based on this observation, a paper-based sensor has been developed to detect gossypol with a limit of detection (LOD) of 2.9 nM.

Augmenting Antimicrobial Resistance Surveillance: Rapid Detection of β-Lactamase-Expressing Drug-Resistant Bacteria through Sensitized Luminescence on a Paper-Supported Hydrogel.

The emergence of antimicrobial resistance (AMR) in pathogenic bacteria, expedited by the overuse and misuse of antibiotics, necessitates the development of a rapid and pan-territorially accessible diagnostic protocol for resistant bacterial infections, which would not only enable judicious prescription of drugs, leading to infection control but also augment AMR surveillance. In this study, we introduce for the first time a "" terbium (Tb) photoluminescence assay supported on a paper-based platform for rapid point-of-care (POC) detection of β-lactamase (BL)-producing bacteria. We strategically conjugated biphenyl-4-carboxylic acid (), a potent Tb sensitizer, with cephalosporin to engineer a BL substrate , where the energy transfer to terbium is arrested.

A photoluminescence assay with a portable device for rapid, sensitive and selective detection of europium and terbium.

Rare earth elements are essential in many real-life applications, but their steady supply is being affected by multiple challenges. The recycling of lanthanides from electronic and other waste is thus gaining momentum which makes the detection of lanthanides with high sensitivity and selectivity a critical area of research. We now report a paper-based photoluminescent sensor for the rapid detection of terbium and europium with low detection limit (nM), which has the potential to facilitate recycling processes.

Ratiometric rapid distinction of two structurally similar fluoroquinolone antibiotics by a Tb/Eu hydrogel.

Norfloxacin and ofloxacin are two frequently prescribed second-generation fluoroquinolone antibiotics with an identical 4-quinolone chromophore and hence, are difficult to distinguish by conventional methods (UV or fluorescence). We have designed a Tb/Eu/cholate cocktail that enabled us to differentiate these two drugs and rapidly measure their concentrations when present together. Additionally, a Tb-cholate gel-based paper sensor was developed to detect and quantify them in a single drug containing system with a limit of detection (LOD) well below 100 nM.

Secondary Nucleation-Triggered Physical Cross-Links and Tunable Stiffness in Seeded Supramolecular Hydrogels.

Mechanistic understanding and the control of molecular self-assembly at all hierarchical levels remain grand challenges in supramolecular chemistry. Functional realization of dynamic supramolecular materials especially requires programmed assembly at higher levels of molecular organization. Herein, we report an unprecedented molecular control on the fibrous network topology of supramolecular hydrogels and their resulting macroscopic properties by biasing assembly pathways of higher-order structures.

Energy transfer in FRET pairs in a supramolecular hydrogel template.

Fluorescence resonance energy transfer (FRET) in pairs of chromophores has mostly been achieved using covalently bound chromophores. In this study, we have demonstrated energy transfer in FRET pairs by taking advantage of the self-assembly of the chromophores on metal cholate hydrogel fibers.

Naked-Eye Detection of Hydrogen Peroxide on Photoluminescent Paper Discs.

We have developed a turn-on photoluminescence protocol to detect hydrogen peroxide (HO) utilizing a supramolecular hydrogel as a sensing platform. Hydrogen peroxide is widely used in formulations, starting from healthcare products to explosives. It is also known to induce deleterious health effects at its irregular physiological concentration and considered as a biomarker in various disease conditions.

An Inexpensive Paper-Based Photoluminescent Sensor for Gallate Derived Green Tea Polyphenols.

This work describes a terbium luminescence-based protocol to selectively detect gallate-derived green tea polyphenols on a supramolecular gel immobilised paper platform for the first time. This user-friendly, inexpensive (€ 0.0015) approach requires very low sample volumes for the analysis.

An inexpensive and sensitive turn-on luminescence protocol for sensing formaldehyde.

Formaldehyde (FA), the simplest and most widely-used aldehyde, can pose serious health issues when present at elevated concentrations. Here, we report a "turn-on" terbium photoluminescence method for the efficient detection of FA. A pro-sensitizer molecule was designed and synthesised, which releases the sensitizer in the presence of FA inside the terbium cholate hydrogel matrix, resulting in a "turn-on" luminescence response.

Supramolecular Gelation of Europium and Calcium Cholates through the Nucleation-Elongation Growth Mechanism.

A detailed understanding of gelation mechanism can enable the properties of gels to be tuned for various applications, and may possibly help in understanding the aggregation of different biomolecules. We report a detailed study of the morphological and physio-chemical changes, dynamics (of a probe), and kinetics during the gelation of europium and calcium cholate hydrogels, leading to the development of a growth model. AFM images showed the transition of aggregated particles (100-150 nm) in the sol phase growing to a fibrous network in the gel through the entanglement of fibres, and not by dendritic growth (height analysis).

Nanofiber-Directed Anisotropic Self-Assembly of CdSe-CdS Quantum Rods for Linearly Polarized Light Emission Evidenced by Quantum Rod Orientation Microscopy.

Hybrid soft materials composed of CdSe-CdS nanorods or "quantum rods" (QRs) and the fluorescent 2,3-didecyloxyanthracene (DDOA) low molecular weight organogelator are obtained through self-assembly. Spectroscopy, microscopy, and rheology studies show that the QRs and DDOA coassemble, thereby stabilizing the organogels. Depending on the QR load and excitation wavelength, single nanofibers (NFs) of the hybrid gel display either sharp polarized red luminescence (under green excitation), or dual perpendicularly polarized blue and red emissions (under UV excitation).

Eu/Tb luminescence for alkaline phosphatase and β-galactosidase assay in hydrogels and on paper devices.

Simple technologies for efficient detection of important (bio)molecules are always in great demand. We now report the detection and assay of two biologically important enzymes, alkaline phosphatase and β-galactosidase, in Eu- or Tb-based cholate hydrogels, respectively, and on filter paper discs coated with such hydrogels. Pro-sensitizers derived from 1-hydroxypyrene and 2,3-dihydroxynaphthalene were incorporated into Eu or Tb cholate hydrogels, respectively.

A self-assembled CdSe QD-organogel hybrid: photophysical and thermoresponsive properties.

A luminescent hybrid gel was prepared by incorporating organic ligand capped CdSe quantum dots (QDs) into a steroid-dimer derived organogel. Photophysical measurements and electron microscopy studies allowed us to understand the nature of the hybrid. Detailed analysis of the excited state dynamics of the hybrid was carried out using a kinetic decay model.

Instant room temperature synthesis of self-assembled emission-tunable gold nanoclusters: million-fold emission enhancement and fluorimetric detection of Zn .

Facile synthesis of luminescent metal nanoclusters (NCs) accompanied by emission color tuning is currently an active area of research. In this work we describe a rapid (1 s) room temperature synthesis of luminescent Au NCs from completely nonluminescent NCs through the incorporation of Zn. The nanoclusters are initially stabilized by mercaptopropionate, and the coordination of Zn with the carboxylate groups of the ligands rigidifies the Au(i) thiolates restricting the intramolecular rotation-vibrational motion.

In situ formation of luminescent CdSe QDs in a metallohydrogel: a strategy towards synthesis, isolation, storage and re-dispersion of the QDs.

A one step, in situ, room temperature synthesis of yellow luminescent CdSe QDs was achieved in a metallohydrogel derived from a facially amphiphilic bile salt, resulting in a QD-gel hybrid. An ordered self-assembly and homogeneous distribution of the CdSe QDs in the hydrogel network was observed from optical and electron micrographs. The different excited state behavior of the CdSe QDs in the hybrid was revealed for the first time using time resolved spectroscopy.

Metallogels of indium(iii) with bile salts: soft materials for nanostructured InS synthesis.

This work describes sonication mediated facile metallo-hydrogel formation from biodetergents sodium cholate and deoxycholate in the presence of indium(iii). The resulting thermo-irreversible gels behaved as viscoelastic soft solids as observed by rheological measurements. Scanning electron and atomic force microscopy analysis revealed the transition from spherical aggregates before gelation to typical entangled three-dimensional fibrous networks in gels.

Luminescence Resonance Energy Transfer in a Multiple-Component, Self-Assembled Supramolecular Hydrogel.

Cascade energy transfer from a sensitizer to Tb then to fluorescent dyes was studied for the first time in a supramolecular hydrogel. Efficient energy transfer from Tb to the dyes was observed, as established by time-delayed emission and excitation spectral analysis, lifetime data, and microscopic studies.

Hierarchical self-assembly of photoluminescent CdS nanoparticles into a bile acid derived organogel: morphological and photophysical properties.

We have described a strategy towards integrating photoluminescent semiconductor nanoparticles into a bio-surfactant derived organogel. A facially amphiphilic bile thiol was used for capping CdS nanoparticles (NPs) which were embedded in a bile acid derived new organogelator in order to furnish a soft hybrid material. The presence of CdS NPs in a well-ordered 1D array on the organogel network was confirmed using microscopic techniques.

A Stimuli-Responsive Metallohydrogel Exhibiting Cyclohexane-Like Hydrophobicity.

Silver(I) forms a hydrogel in the presence of cholate with unusual properties, which are not observed with other cations. Polarity-sensitive probes have shown that the spherical aggregates observed in the gel have 'pockets' with hydrophobicity comparable to that of degassed cyclohexane. The gel exhibited thermo- and mechanoresponsive properties.

A novel strategy towards designing a CdSe quantum dot-metallohydrogel composite material.

We have described here an efficient method to disperse hydrophobic CdSe quantum dots (QDs) in an aqueous phase using cetyltrimethylammonium bromide (CTAB) micelles without any surface ligand exchange. The water soluble QDs were then embedded in 3D self assembled fibrillar networks (SAFINs) of a hydrogel showing homogeneous dispersibility as evidenced from optical and electron microscopic techniques. The photophysical studies of the hydrogel-QD composite are reported for the first time.

The interface makes a difference: lanthanide ion coated vesicles hydrolyze phosphodiesters.

Lanthanide ions are strong Lewis acids. Their complexation to a variety of ligands can further enhance their Lewis acidity allowing the hydrolysis of phosphoesters and even DNA. We show that the interaction of lanthanide ions with vesicles from zwitterionic phosphatidylcholine lipids gives supramolecular structures in which the metal ion is loosely coordinated to the surface.

Terbium(III)-cholate functionalized vesicles as luminescent indicators for the enzymatic conversion of dihydroxynaphthalene diesters.

The phosphorescence intensity of unilamellar DOPC vesicles with embedded Tb(3+)-cholate complexes depends on the concentration of dihydroxynaphthalene (DHN) as sensitizer in solution. This was used to monitor the enzymatic conversion of DHN esters or DHN glucosides by enzymes in aqueous buffered solution.

Tb3+ sensitization in a deoxycholate organogel matrix, and selective quenching of luminescence by an aromatic nitro derivative.

In this article, we present the discovery of a metallo-organogel derived from a Tb(3+) salt and sodium deoxycholate (NaDCh) in methanol. The gel was made luminescent through sensitization of Tb(3+) by doping with 2,3-dihydroxynaphthalene (DHN) in micromolar concentrations. Rheological measurements of the mechanical properties of the organogel confirmed the characteristics of a true gel.

Organogels from dimeric bile acid esters: in situ formation of gold nanoparticles.

A new class of steroid dimers (bile acid derivatives) linked through ester functionalities were synthesized, which gelled various aromatic solvents. The organogels formed by the three dimeric ester molecules showed birefringent textures and fibrous nature by polarizing optical microscopy and scanning electron microscopy, respectively. A detailed rheological study was performed to estimate the mechanical strengths of two sets of organogels.