A novel fluoro-chromogenic Cu2+ probe for living-cell imaging based on rhodamine 6G-pyridine conjugation

Novel coumarin-based ratiometric bifunctional fluorescent probe mimicking a set-reset memorized device

A novel coumarin-based fluorescent sensor CHE, incorporating 2-hydrazinylbenzothiazole and coumarin aldehyde, has been developed that demonstrated a preferential detection of Hg2+ and Ag+ in presence of interferences. Compared to previously prevalent intensity-based fluorescent probes, CHE exhibited a ratiometric fluorescence response to Hg2+ and Ag+, and further accurately differentiated Hg2+ and Ag + using the differential extractive ability of EDTA when interacting with ion-CHE complexes. Sensing mechanism was investigated and elucidated. The chemosensor CHE was successfully applied to detect Hg2+ and Ag+ in six distinct samples with satisfactory results. Additionally, combinatorial logic circuits were constructed utilizing three distinct logic gates (NOT, OR, and INH) based on the sensor's differential output signals in response to Hg2+/Ag+ and other cations. Interestingly, utilizing the reversible and reproducible switching behavior of the EDTA interaction with Hg2+, a conceptual 'Write-Read-Erase-Read' memory function with multi-write capability was proposed, offering a novel perspective for molecular-based memory systems.

Pyrene-acylhydrazone-based Turn-on Fluorescent Probe for Highly Sensitive Detection Cu2+ and Application in Bioimaging

The development of highly selective and sensitive, low detection limits, and biocompatible turn-on copper ion fluorescent probes is of great significance for the environment and life sciences. In this study, a novel turn-on fluorescent probe T based on pyrene-acylhydrazone was synthesized via an efficient one-step condensation reaction and characterized by 1H NMR, 13C NMR and HRMS. The probe T exhibited high selectivity with a low detection limit of 0.304 nM towards Cu2+ in DMSO/H2O (v/v = 1 : 1) medium by a PET-TICT dual interplaying sensing mechanisms. Job's plot analysis and HRMS data confirmed the 1 : 1 binding stoichiometry between T and Cu2+ with an association constant of 5.7×103 M-1. Additionally, the binding model was investigated by 1H NMR titration and FT-IR spectra. Furthermore, probe T exhibits low cellular toxicity and excellent membrane permeability, and has been successfully applied for fluorescent imaging of copper ions in live HT-22 cells.

Colorimetric Cu2+ Detection of (1E,2E)-1,2-Bis((1H-pyrrol-2-yl)methylene)hydrazine Using a Custom-Built Colorimeter

The compound (1E,2E)-1,2-bis((1H-pyrrol-2-yl)methylene)hydrazine (1) was investigated for its chemosensor application. The colorimetric response of 1 with various ions was investigated, and the selective optical change upon mixing with Cu²⁺ was found. The Cu²⁺ binding stoichiometry of 1 derived from Job's plot and the in silico study give us the tentative structural detail of the binding mode of 1 and Cu²⁺ being 1:1. The binding constant between 1 and Cu²⁺ from the Benesi-Hildebrand plot was 1.49 × 10⁴ M^-1. The limit of detection of 1 in Cu²⁺ detection was 0.64 μM (0.040 ppm), which is much lower than the WHO and US EPA maximum allowable Cu²⁺ level in drinking water (2 and 1.3 ppm, respectively). The custom-built colorimeter demonstrates a good linear relationship between Cu²⁺ concentration and electrical resistance (Ω) upon 1-Cu²⁺ ion binding.

A pH-applicative fluorescent probe with long measuring range for monitoring hydrazine in water samples and Arabidopsis thaliana

In this work, a fluorescent probe, RhodCl-Hz, with pH-applicative capability and long measuring range, was developed to serve the topic on the enrichment process of hydrazine. It was practical due to the clear acid-base boundary and the sectioned linear ranges. With the excitation wavelength of 515 nm and the emission peak at 565 nm, the detecting system was steady. It exhibited a clear cut-off point at pH 7.0 and steady fluorescence signals within the range of 7.0-10.0. As a whole, the linear range of 10.0-500 µM (1.0-50.0 equivalent) was long. The Limit of Detection value was calculated as 0.64 μM. With high selectivity, RhodCl-Hz was applied to suit water samples and biological imaging in both Arabidopsis Thaliana root tips and living MCF-7 cells. The information here might be helpful for revealing the enrichment process of hydrazine.

A novel near-infrared turn-on and ratiometric fluorescent probe capable of copper(ii) ion determination in living cells

A near-infrared ratiometric fluorescent probe CR-Ac based on a coumarin-benzopyrylium platform has been developed for selective detection of Cu2+. The cell imaging data revealed the capabilities of CR-Ac in monitoring the dynamic changes of subcellular Cu2+ and the quantification of Cu2+ levels in living cells.

A hydrophilic naphthalimide-based fluorescence chemosensor forCu2+ ion: Sensing properties, cell imaging and molecular logic behavior

In this work, a hydrophilic naphthalimide-based fluorescence chemosensor (sensor 1) was synthesized for Cu²⁺ recognition, in which 2-(2-aminoethoxy)ethanol was introduced to improve the hydrophily and Schiff base acted as the multidentate ligand for Cu²⁺. The effect factors, sensing mechanism and regenerability of sensor 1 for Cu²⁺ sensing were systematically investigated. It was found that sensor 1 displayed a long emission wavelength of 532 nm upon excited in visible light region (436 nm), and the good water solubility made it utilized in aqueous media. It could selectively react with Cu²⁺ over other common metal ions to form a 2:1 complex within 1 min and result in significant fluorescence quench. The fluorescence change was linear to 0.5-10.0 μmol L^-1 of Cu²⁺ with a low detection limit of 3.74 × 10^-8 mol L^-1. Sensor 1 has been successfully utilized for analyzing Cu²⁺ in water samples as well as imaging cellular Cu²⁺. Moreover, in view of fluorescence "on-off-on" switches of sensor 1 induced by Cu²⁺ and EDTA, an IMPLICATION logic gate was constructed based on fluorescence mode with Cu²⁺ and EDTA as inputs.

Mechanochromic double network hydrogels as a compression stress sensor

We prepared tough DN hydrogels with various rhodamine contents that undergo colour changes with external stresses. We demonstrated a facile platform between macroscopic colour changes and external stresses via converting photographs to mechanographs.

Development of a new fluorescent probe for cysteine detection in processed food samples

Cysteine is a crucial amino acid, found in a huge amount in protein-rich foods. We focused our research to determine the amount of free cysteine consumed highly in foods such as pork, beef, poultry, eggs, dairy, red peppers, soybeans, broccoli, brussels sprouts, oats, and wheat germs. A newly designed carbazole-pyridine-based fluorescent probe (CPI) has been introduced for quantitative estimation of cysteine (Cys) with a "turn on" fluorescence in some popular processed food samples chosen from our daily diet. CPI shows both naked eye and UV-visible color changes upon interaction with cysteine. The binding approach between CPI and Cys at biological pH has been thoroughly explored by UV-visible and fluorescence spectroscopy. From Job's plot analysis, 1:1 stoichiometric reaction between CPI and Cys is observed with a detection limit of 3.8 μM. NMR, ESI mass spectrometry, and time-dependent density functional theory (TD-DFT) study enlightens the formation of more stable product CPI-Cys. The "turn on" response of the probe CPI occurs due to the interruption of intra-molecular charge transfer (ICT) process upon reacting with cysteine. Moreover, CPI is a very stable, cost-effective compound and exhibits excellent real-time selectivity towards Cys over all other comparative biorelevant analytes. Interestingly, our proposed method is much advantageous as it is able to estimate cysteine predominantly by screening out other comparative biocomponents found in different protein-rich foods.