Davydov Split Aggregates of Cyanine Dyes on Self-Assembled Nanotubes

A novel near-infrared polymethine dye biosensor for rapid and selective detection of lithocholic acid

Lithocholic acid (LCA), a secondary bile acid, has emerged as a potential early diagnostic biomarker for various liver diseases. In this study, we introduce a novel near-infrared (NIR) polymethine dye-based biosensor, capable of sensitive and selective detection of LCA in phosphate buffer and artificial urine (AU) solutions. The detection mechanism relies on the formation of J-aggregates resulting from the interplay of 3,3-Diethylthiatricarbocyanine iodide (DiSC2(7)) dye molecules and LCA, which induces a distinctive red shift in both absorption and fluorescence spectra. The biosensor demonstrates a detection limit for LCA of 70 μM in PBS solution (pH 7.4), while in AU solution, it responds to an LCA concentration as low as ∼60 μM. Notably, the proposed biosensor exhibits outstanding selectivity for LCA, effectively distinguishing it from common interferents such as uric acid, ascorbic acid, and glucose. This rapid, straightforward, and cost-effective spectrometer-based method underscores its potential for early diagnosis of liver diseases by monitoring LCA concentrations.

Crystalline H-Aggregate Nanoparticles for Detecting Dopamine Release from M17 Human Neuroblastoma Cells

Dopamine (DA) is an important neurotransmitter, which is essential for transmitting signals in neuronal communications. The deficiency of DA release from neurons is implicated in neurological disorders. Therefore, there has...

Fluorescent H-Aggregate Vesicles and Tubes of a Cyanine Dye and Their Potential as Light-Harvesting Antennae

H-aggregates of π-conjugated dyes are an ordered supramolecular structure. However, the non-fluorescence behavior of H-aggregates greatly limits their potential applications. In this paper, we report the formation of fluorescent H-aggregates with vesicular and tubular morphologies by the self-assembly of 3,3'-diethylthiacarbocyanine iodide (DiSC₂(3)) in ammonia/methanol mixtures. The transition from H-aggregate vesicles to H-aggregate tubes can be achieved by increasing the volume fraction of methanol in the mixtures. H-aggregate vesicles and tubes show two blue-shifted absorption bands and strong fluorescence, which result from the inclined arrangement of DiSC₂(3) molecules. Furthermore, light-harvesting complexes are formed by adding dopamine (DA)-quinone (acceptor) in synthetic urine with H-aggregate vesicles or tubes. Our results show that H-aggregate tubes are more efficient than H-aggregate vesicles in transferring excited electrons to DA-quinone acceptors.

Nanotube Template-Directed Formation of Strongly Coupled Dye Aggregates with Tunable Exciton Fluorescence Controlled by Switching between J- and H-Type Electronic Coupling

Strongly coupled dye aggregates with tailored exciton properties may find their use in developing artificial light-harvesting and optoelectronic devices. Here, we report the control of tubular pseudoisocyanine (PIC) dye J- and H-aggregate formation with tunable exciton fluorescence using lithocholic acid (LCA) as a template. The LCA-templated PIC J-aggregate nanotubes formed at a higher LCA/PIC molar ratio (≥5:1) exhibit a sharp, red-shifted absorption band (at 555 nm), intense fluorescence (at 565 nm), and shorter lifetime (200 ps), all indicating their strong superradiance properties. In contrast, the H-aggregate nanotubes formed at a lower LCA/PIC molar ratio (2:1) exhibit a significantly blue-shifted absorption band (at 420 nm) and highly red-shifted fluorescence emission (at 600 nm) with enhanced lifetime (4.40 ns). The controlled switching of the optical properties of the PIC dye aggregates achieved by controlling the LCA/PIC molar ratio could serve as an important guideline for the design of organic photo-functional materials.