The impact of metal coordination on the assembly of bis(indolyl)methane-naphthalene-diimide amphiphiles

Synthesis of Phenol-Hydrazide-Appended Tetraphenylethenes as Novel On-Off-On Cascade Sensors of Copper and Glutathione

This study reports the synthesis of novel fluorescent probes, phenol-hydrazide-appended tetraphenylethenes (TPEs I and II), and explores their photochemical properties. The probes exhibit aggregation-induced emission (AIE) in increasing water content, as observed using fluorescence spectroscopy. Further investigation with UV-vis and fluorescence techniques revealed their potential as ion sensors. Both TPE I and TPE II act as "turn-off" sensors for Cu2+ ions, showing decreased fluorescence intensity in their presence. Their limit of detection (LOD) and association constant (K a) for Cu2+ were found to be comparable at 747 nM/597 nM, and 2.46 × 105 M-1/2/1.78 × 105 M-1/2, respectively. Moreover, the quantum yields of TPE I and TPE II were also calculated and found to be 0.651 and 0.325, respectively. Interestingly, these probes also function as "turn-on" sensors for glutathione (GSH) in the presence of copper. This means their fluorescence can be reversibly switched off and on by alternating CuCl2 and GSH additions. Moreover, the LOD values for GSH with TPE II-Cu2+ were calculated to be 544 nM. In addition, the investigation also employed visual analysis to assess the color alterations of TPEs on filter paper and in real water samples. Overall, this research introduces promising new probes with potential applications in copper ion detection and biomolecule glutathione sensing in real water samples.

Off-On-Off Cascade Recognition of Cyanide, Mercury, and Aluminum Using N/5-Monosubstituted Rhodanines

This study aims to synthesize N- and 5-monosubstituted rhodanine derivatives as ion-sensing organics and investigate their sensing abilities. Following an easy and green approach to synthesis, the anion-sensing properties of the rhodanines were studied using colorimetric detection and spectroscopic methods. As a result of studies, rhodanines are found to be highly solvent-controlled colorimetric and fluorescent cyanide, mercury, and aluminum sensors. The stoichiometry of the interaction between CN- and both probes was determined to be 1:1 using Job's plot analysis. The binding constants (Ks) of CN- to 5-arylRh and N-arylRh were calculated to be 3.25 × 104 and 7.07 × 104 M-1, respectively, demonstrating their high affinity for cyanide ions. The limits of detections for the 5-arylRh and N-arylRh were also determined as 356 and 617 nM, respectively. In addition to detecting CN-, 5-arylRh also serves as a specific turn-off sensor for mercury and aluminum when cyanide and hydroxide are present. This enables the fluorescence intensity to be toggled on/off by alternating the addition of CN-/OH- and Hg2+/Al3+. Furthermore, the LOD values for Hg2+ and Al3+ with 5-arylRh-CN- and 5-arylRh-OH- were determined to be 414 nM and 1.35 μM, respectively. Furthermore, the turn-on binding mechanisms of 5-arylRh and N-arylRh with cyanide ions were elucidated, and the experimental band gap (highest occupied molecular orbital/least unoccupied molecular orbital) energy values corroborated the proposed mechanism. Additionally, the interaction mechanism of the probes with CN- was further investigated by using the 1H NMR technique. Collectively, these findings suggest that 5-arylRh, N-arylRh, and 5-arylRh-CN- hold promise as selective and sensitive candidate sensors for CN-, Hg2+, and Al3+ ions.

Tools to enable the study and translation of supramolecular amphiphiles

This tutorial review focuses on providing a summary of the key techniques used for the characterisation of supramolecular amphiphiles and their self-assembled aggregates; from the understanding of low-level molecular interactions, to materials analysis, use of data to support computer-aided molecular design and finally, the translation of this class of compounds for real world application, specifically within the clinical setting. We highlight the common methodologies used for the study of traditional amphiphiles and build to provide specific examples that enable the study of specialist supramolecular systems. This includes the use of nuclear magnetic resonance spectroscopy, mass spectrometry, X-ray scattering techniques (small- and wide-angle X-ray scattering and single crystal X-ray diffraction), critical aggregation (or micelle) concentration determination methodologies, machine learning, and various microscopy techniques. Furthermore, this review provides guidance for working with supramolecular amphiphiles in in vitro and in vivo settings, as well as the use of accessible software programs, to facilitate screening and selection of druggable molecules. Each section provides: a methodology overview - information that may be derived from the use of the methodology described; a case study - examples for the application of these methodologies; and a summary section - providing methodology specific benefits, limitations and future applications.

A highly sensitive hemicyanine-based near-infrared fluorescence sensor for detecting toxic amyloid aggregates in human serum

The development of an accurate and sensitive sensor for detecting amyloid plaques, which are responsible for many protein disorders like Alzheimer's disease, is crucial for early diagnosis. Recently, there has been a notable increase in the development of fluorescence probes that exhibit emission in the red region (>600 nm), aiming to effectively tackle the challenges encountered when working with complex biological matrices. In the current investigation, a hemicyanine-based probe, called LDS730, has been used for the sensing of amyloid fibrils, which belong to the Near-Infrared Fluorescence (NIRF) family of dyes. NIRF probes provide higher precision in detection, prevent photo-damage, and minimize the autofluorescence of biological specimens. The LDS730 sensor emits in the near-infrared region and shows a 110-fold increase in fluorescence turn-on emission when bound to insulin fibrils, making it a highly sensitive sensor. The sensor has an emission maximum of ~710 nm in a fibril-bound state, which shows a significant red shift along with a Stokes' shift of ~50 nm. The LDS730 sensor also displays excellent performance in the complicated human serum matrix, with a limit of detection (LOD) of 103 nM. Molecular docking calculations suggest that the most likely binding location of LDS730 in the fibrillar structure is the inner channels of amyloid fibrils along its long axis, and the sensor engages in several types of hydrophobic interactions with neighboring amino acid residues of the fibrillar structure. Overall, this new amyloid sensor has great potential for the early detection of amyloid plaques and for improving diagnostic accuracy.

Ppb-Level, Dual Channel Sensing of Cyanide and Bisulfate Ions in Aqueous Medium: Computational Rationalization of Ion-Dependent ICT Mechanism

In this report, three oxidized diindolylarylmethane (DIAM) based chromogenic probes (designated as 1, 2, and 3) have been developed for the simultaneous and dual-channel detection of cyanide (LOD: 6.2 ppb)...