Binding Modes of a Phenylpyridinium Styryl Fluorescent Dye with Cucurbiturils

In order to explore how cucurbituril hosts accommodate an N-phenyl-pyridinium derivative guest, the complexation of the solvatochromic dye, 4-(4-(dimethylamino)styryl)-1-phenylpyridinium iodide (PhSt) with α,α′,δ,δ′-tetramethyl-cucurbit[6]uril (Me4CB6) and cucurbit[7]uril (CB7) was investigated by absorption spectroscopic, fluorescence and NMR experiments. In aqueous solutions, PhSt forms 1:1 complexes with both cucurbiturils, the complex with CB7 has a higher stability constant (Ka = 6.0 × 106 M−1) than the complex with Me4CB6 (Ka = 1.1 × 106 M−1). As revealed by NMR experiments and confirmed by theoretical calculations, CB7 encapsulates the whole phenylpyridinium entity of the PhSt cation guest, whereas the cavity of Me4CB6 includes only the phenyl ring, the pyridinium ring is bound to the carbonyl rim of the host. The binding of PhSt to cucurbiturils is accompanied by a strong enhancement of the fluorescence quantum yield due to the blocking of the deactivation through a twisted intramolecular charge transfer (TICT) state. The TICT mechanism in PhSt was characterized by fluorescence experiments in polyethylene glycol (PEG) solvents of different viscosities. The PhSt-CB7 system was tested as a fluorescence indicator displacement (FID) assay, and it recognized trimethyl-lysine selectively over other lysine derivatives.

Towards Mycobacterium tuberculosis detection at the point-of-care: a brighter solvatochromic probe permits the detection of mycobacteria within minutes

ABSTRACTThere is an urgent need for point-of-care tuberculosis (TB) diagnostic methods that are fast, inexpensive, and operationally simple. Here, we report on a bright solvatochromic dye trehalose conjugate that specifically detects Mycobacterium tuberculosis (Mtb) in minutes. 3-hydroxychromone (3HC) dyes, known to yield high fluorescence quantum yields, exhibit shifts in fluorescence intensity in response to changes in environmental polarity. We synthesized two analogs of 3HC-trehalose conjugates (3HC-2-Tre and 3HC-3-Tre) and determined that 3HC-3-Tre has exceptionally favorable properties for Mtb detection. 3HC-3-Tre-labeled mycobacterial cells displayed a 10-fold increase in fluorescence intensity compared to our previously reports on the dye 4,4-N,N-dimethylaminonapthalimide (DMN-Tre). Excitingly, we detected fluorescent Mtb cells within 10 minutes of probe treatment. Thus, 3HC-3-Tre permits rapid visualization of mycobacteria that ultimately could empower improved Mtb detection at the point-of-care in low-resource settings.

Interaction between Solvatochromic Dyes and Water Sampled from a Natural Source Treated with High Dilutions of Phosphorus

Background Highly diluted and succussed solutions interact with solvatochromic dyes, indicating that changes in solvent and solute polarity could be related to their mechanism of action. It is not known, however, how the activity associated with succussed high dilutions is transferred to untreated water and what the limits of this process are. Aims The aims of the present study were to ascertain whether a succussed high dilution of phosphorus (1.5 × 1−59 M; Phos 30cH) seeded into a natural water source that fed a fjord and two connected lakes could propagate itself through the lake system (total volume 2200 m3) and, moreover, whether the process could be tracked using solvatochromic dyes. Methods Samples of water were collected before and after seeding, at different times and places throughout the lake system. Controls comprised water taken from an untreated and adjacent, but independent, lake (1385 m3). Results Water samples taken up to 72 hours after the source treatment produced significant increases (p ≤ 0.03) in the absorbance of the solvatochromic dye methylene violet (MV), while samples from the control lake produced no changes. Conclusions The study indicates that activity associated with Phos 30c can propagate itself through large volumes of water, causing changes throughout a whole connected lake system, and that these changes can be tracked using the solvatochromic dye MV. This in turn means the use of homeopathic medicines in large volumes of drinking water, in farming and ecological contexts, now has the potential to be assessed with physico-chemical monitoring.

Spectral Characterization of Stem Cell-Derived Myelination within the Injured Adult PNS Using the Solvatochromic Dye Nile Red

Background: Myelin is an essential component of the peripheral and central nervous system, enabling fast axonal conduction and supporting axonal integrity; limited tools exist for analysis of myelin composition in-vivo. Objective: To demonstrate that the photophysical properties of myelin-incorporated solvatochromic dyes can be exploited to probe the biochemical composition of living peripheral nerve myelin at high spatial resolution. Methods: Using the myelin-incorporated fluorescent dye Nile Red we sequentially analyzed the spectral characteristics of remyelinating myelin membranes both in-vitro and in-vivo, including in living rats. Results: We demonstrated a consistent bi-phasic evolution of emission spectra during early remyelination, and visually report the reliable biochemical flux of myelin membrane composition in-vitro and in-vivo. Conclusions: Solvatochromic spectroscopy enables the analysis of myelin membrane maturity during remyelination, and can be performed in-vivo. As the formation of myelin during early-to-late remyelination likely incorporates fluctuating fractions of lipophilic components and changes in lateral membrane mobility, we propose that our spectrochemical data reflects the observation of these biochemical processes.

Plasticizer-free and pH-independent ion-selective optode films based on a solvatochromic dye

A layer of a solvatochromic dye, an ionophore, and an ion-exchanger deposited on a Nylon membrane enables highly selective colorimetric and fluorometric ion sensing.

Potential modulations in flatland: near-infrared sensitization of MoS2 phototransistors by a solvatochromic dye directly tethered to sulfur vacancies

Near-infrared sensitization of monolayer MoS2 is here achieved via the covalent attachment of a novel heteroleptic nickel bis-dithiolene complex into sulfur vacancies in the MoS2 structure. Photocurrent action spectroscopy of the sensitized films reveals a discreet contribution from the sensitizer dye centred around 1300 nm (0.95 eV), well below the bandgap of MoS2 (2.1 eV), corresponding to the excitation of the monoanionic dithiolene complex. A mechanism of conductivity enhancement is proposed based on a photo-induced flattening of the corrugated energy landscape present at sulfur vacancy defect sites within the MoS2 due to a dipole change within the dye molecule upon photoexcitation. This method of sensitization might be readily extended to other functional molecules that can impart a change to the dielectric environment at the MoS2 surface under stimulation, thereby extending the breadth of detector applications for MoS2 and other transition metal dichalcogenides.