A ratiometric fluorescent probe for the rapid and specific detection of HSO3 - in water samples

A near-infrared amine/HSO3- probe with colorimetric and fluorescent ultrafast response and its application in food samples and visual evaluation of salmon freshness

A multifunctional near-infrared fluorescent probe (Sycy) is synthesized by the one-step condensation reaction of syringaldehyde and tricyanofuran. Sycy can detect HSO3- within 150 s in the red wine and sugar samples with a low detection limit of 3.5 μM. Sycy also has an obvious response to 13 volatile amines through colorimetric and fluorescent channels. Sycy recognizes representative diethylamine (DEA) with a large stokes shift (131 nm), low detection limit (7.11 μM), ultrafast response within 5 s, and fluorescence imaging DEA in living cells. The sensing tag loaded with Sycy can monitor the freshness of salmon by observing colorimetrical and fluorescent changes of the tag with the naked eye. In addition, quantitative determination of HSO3- and evaluation of fish freshness can be achieved with smartphone assistance, improving the detection accuracy. Sycy can be prepared into fluorescent ink and be applied to the field of material and information storage.

A highly sensitive ratiometric fluorescence probe for sensing and imaging sulfite in food samples and living cells

In this work, a ratiometric and chromogenic fluorescent probe 1 was synthesized for the detection of SO32-. The probe 1 at PBS (10 mM, pH = 7.4) presented a marked emission band at 661 nm. Upon addition of SO32- ions, a highly emissive adduct with a marked fluorescence at 471 nm were obtained through a Michael addition. The probe 1 displayed a noticeable fluorescence ratiometric response with a large shift (190 nm) in emission wavelength. The probe can quantitatively detect SO32- with high specificity, fast response (within 130 s) as well as low detection limit (13 nM), and a large Stokes shift (139 nm). Fluorescence imaging of HeLa cells indicated that 1 could be used for monitoring the intrinsically generated intracellular SO32- in living cells by ratiometric fluorescence imaging. Furthermore, 1 could be application in real water and sugar samples with high sensitivity and good recoveries.

Theoretical Investigation on Proton Transfer Directionality and Dynamics Behavior of 3-(Benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde with Two Asymmetric Proton Acceptors

A detailed theoretical investigation on the excited state intramolecular proton transfer (ESIPT) directionality and dynamics behavior of 3-(benzo[d]thiazol-2-yl)-2-hydroxy-5-methoxybenzaldehyde (BTHMB) with two unsymmetric proton acceptors (N and O2) has been performed. The hydrogen bond O1-H···N in BTHMB-a formed by the O1-H group with the N atom or O1-H···O2 in BTHMB-b formed by the O1-H group with the O2 atom is enhanced upon photoexcitation, and the strength of the O1-H···N bond is stronger, which will drive the O1-H proton to the N atom. Potential energy curves further confirm that ESIPT occurs in the N atom because of the smaller energy barrier (0.39 kcal/mol). Results of dynamics simulations manifest that no surface hopping exists between the S0 and S1 states within 300 fs, and ESIPT time constants of BTHMB-a and BTHMB-b are 48 and 151 fs, respectively. While the reverse ESIPT is observed in BTHMB-b at 294 fs, implying that the O1-H proton is transferred to the N atom instead of the O2 atom. The consistency of the calculated absorption (390 nm) and fluorescence spectra (443 and 602 nm) of BTHMB-a with the experimental values (390, 410, and 605 nm) confirms this conclusion again. The charge distribution analysis shows that the charge on the proton acceptors increases, and the O2 atom has higher electronegativity because it has more negative charges. The minimum surface electrostatic potential on the N atom in BTHMB-b correlating with the pKb value is -47.38 kcal/mol, indicating that the N atom has strong basicity. Therefore, the basicity of the N atom dominates the ESIPT process rather than the electronegativity of the O2 atom.

Construction of mitochondria targeted and FRET based ratiometric sensing nanoplatform for sulfur dioxide accurate detection in vitro and in vivo

Sulfur dioxide (SO₂) is a key molecule in organisms that is involved in the regulation of different physiological procedures. Aberrant SO₂ causes a variety of diseases, such as cancer and neurodegeneration. Thus, sensitive and selective detection of SO₂ is of great importance. Based on the Förster resonance energy transfer (FRET) between green fluorescence carbon dots (GCDs) donor and amide-linked near-infrared fluorescence emissive organic small molecular dye (CDDBT) acceptor, one ratiometric fluorescent nano platform, Mito-GCDs-CDDBT for mitochondria SO₂ sensing was constructed. In this FRET sensing system, CDDBT served as the receptor for SO₂, and the presence of SO₂ enhanced GCDs green fluorescence signal and quenched CDDBT near-infrared fluorescence signal due to the disruption of FRET. Mito-GCDs-CDDBT could sensitively detect SO₂ with a detection limit of as low as 0.701 μM. Meanwhile, Mito-GCDs-CDDBT achieved fluorescence imaging to measure the response of cellular exogenous and endogenous SO₂ with remarkable mitochondrial targeting. Moreover, Mito-GCDs-CDDBT also realized SO₂ sensing in vivo including zebrafish and mice. The as-prepared versatile nanoplatform displayed several advantages, such as mitochondria targeting, FRET-based sensitive detection, and sensing capabilities in biological milieu. Potentially, it could be applied in the diagnostics of SO₂ involved diseases.

A novel dehydroabietic acid-based turn-on fluorescent probe for the detection of bisulfite and its application in live-cell and zebrafish imaging

A novel “Turn-on” fluorescent probe, which displayed prominent sensitivity and selectivity for the detection of HSO3−, was synthesized from dehydroabietic acid. The probe also showed high lysosome-targeting properties when sensing HSO3− in MCF-7 cells.