Dual-responsive fluorescence probe for measuring HSO3- and viscosity and its application in living cells and real foods

A colorimetric fluorescent probe for reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO- and its application in food and bioimaging

In view of the significant role of reactive sulfur species (RSS) and reactive oxygen species (ROS) in maintaining the redox homeostasis of organisms, we proposed a colorimetric fluorescent probe (HTN) for reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO-. C = C is the active site for the Michael addition of HSO3- and the oxidation of ClO-. When HTN interacts with HSO3- and ClO-, it exhibits fluorescence quenching. The addition of oxidizing H2O2 to the system can restore the conjugate structure of the addition product of HSO3- (HTN-HSO3-) and the fluorescence recovery, but it cannot restore the structure of the oxidation product of ClO- (HTN-ClO-). By studying the change of the reversibility/non-reversibility of the probe structure with the addition of H2O2, the purpose of reversible detection of HSO3-/H2O2 and distinguishing HSO3-/ClO- is achieved. In addition, HTN can not only be used as a fluorescent ink to detect HSO3- on the test paper, but also has excellent detection effect on HSO3- and ClO- in real food samples and water samples. Meantime, HTN has good biocompatibility and can target mitochondria to achieve reversible detection of HSO3-/H2O2 and effective discrimination of HSO3-/ClO- in living cells. Therefore, HTN has great potential as a molecular tool for studying redox homeostasis in the interaction network of complex living systems.

Unravelling the recent advancement in fluorescent probes for detection against reactive sulfur species (RSS) in foodstuffs and cell imaging

Sulfur-containing representative HSO3-/SO32-, H2S, and biothiols (Cys, Hcy, and GSH) present in food items and biological organisms have raised substantial global concerns about food safety due to their reactivity and potential health implications. Adhering to international health standards is essential for these compounds; in particular, plenty of challenges exist in ensuring product quality in the beverage industry. Many fluorescent probes are being employed in various spectroscopic techniques and have developed rapidly to selectively detect sulfur-related species in food products and bio-sensing for cell imaging. This comprehensive review provides a detailed overview of a wide range of fluorescent probes designed using different fluorophores for detecting reactive sulfur species (RSS) using spectroscopic techniques. Additionally, the review explores the detection of RSS components (HSO3-/SO32-, H2S, and biothiols) in food products and cell imaging using different cell lines, highlighting the crucial role of fluorescent probes in swiftly detecting these analytes in both natural and biological contexts. Furthermore, the review discusses future trends and perspectives, emphasizing the on-going progress in detecting these analytes in food products and cell imaging using various fluorescent probes.

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 FRET/TICT based multifunctional fluorescent probe for the monitoring of SO2 derivatives and viscosity in living cells and real samples

SO2 derivatives and viscosity are important intracellular indicators, which are closely associated with various physiological metabolisms in organisms. The unregulated contents of SO2 derivatives and viscosity in vivo commonly related to some disorders. In this work, probe JFT was developed relying on FRET and TICT mechanisms for the simultaneous detection of SO2 derivatives and viscosity. JFT can rapidly detect viscosity levels with continuously enhanced fluorescence signals at 582 nm basing on the increasing of viscosity. Moreover, JFT was also sensitive to the changes of SO2 derivatives level with a low detection limit (61.5 nM), rapid responding time (with 16 min), excellent selectivity and anti-interference capacity. JFT could detect bisulfite in real water, wine and food samples with high accuracy and recovery rate. Cell imaging indicated that JFT could monitor the endogenous SO2 derivatives and viscosity in mitochondria. Importantly, JFT could recognize the cancer cells basing on the cell imaging difference of JFT in AGS and GES-1 cells.

Improving the sulfite-detection performance of a fluorescent probe via post-synthetic modification with a metal-organic framework

In this work, a post-synthetic modification strategy was attempted to improve the performance of the probe for sulfite detection. The assembled platform UiO-66-NH-DQA, which was acquired by anchoring the sulfite-response fluorescent probe DQA onto the surface of UiO-66-NH2via amide covalent bonds, exhibited enhanced fluorescence intensity and practical intracellular imaging capability. In spite of the structural similarity, as verified by characterization tests, the conversion rate of post-synthetic modification was calculated as 35%, equaling an approximate assembly ratio of 1 : 2 between UiO-66-NH2 and DQA. Most significantly, conversion into UiO-66-NH-DQA led to a 5.6-fold enhancement in the reporting signal with a red shift of 20 nm. For sulfite detection, the linear range was 0-150 μM, with a limit of detection value of 0.025 μM. UiO-66-NH-DQA retained advantages including high stability (within pH 5.0-9.0), rapid response (within 15 min) and high selectivity. Based on low cytotoxicity and relatively rapid cellular uptake, UiO-66-NH-DQA achieved the imaging of both the exogenous and endogenous sulfite levels in living cells. In particular, its rapid cell-permeating capability was guaranteed during the modification. The post-synthetic modification strategy reported herein has potential for improving the practical properties of fluorescent monitoring materials.

Ultrasonic Sensor: A Fast and Non-Destructive System to Measure the Viscosity and Density of Molecular Fluids

This study presents the design and development of an ultrasonic sensor as a fundamental tool for characterizing the properties of fluids and biofluids. The analysis primarily focuses on measuring the electrical parameters of the system, which correlate with the density and viscosity of the solutions, in sample volumes of microliters and with high temporal resolution (up to 1 data point per second). The use of this sensor allows the fast and non-destructive evaluation of the viscosity and density of fluids deposited on its free surface. The measurements are based on obtaining the impedance versus frequency curve and the phase difference curve (between current and voltage) versus frequency. In this way, characteristic parameters of the transducer, such as the resonance frequency, phase, minimum impedance, and the quality factor of the resonant system, can characterize variations in density and viscosity in the fluid under study. The results obtained revealed the sensor's ability to identify two parameters sensitive to viscosity and two parameters sensitive to density. As a proof of concept, the unfolding of the bovine albumin protein was studied, resulting in a curve that reflects its unfolding kinetics in the presence of urea.

Design and Screening of Fluorescent Probes Based upon Hemicyanine Dyes for Monitoring Mitochondrial Viscosity in Living Cells

Viscosity, at the subcellular level, plays a crucial role as a physicochemical factor affecting microenvironment homeostasis. Abnormal changes in mitochondrial viscosity often lead to various diseases in the organism. Based on the twisted intramolecular charge transfer mechanism, four hemicyanine dye fluorescent probes (HT-SA, HT-SA-S, HT-Bzh, and HT-NA) were designed and synthesized for viscosity response. The single bond between the nitrogen-containing heterocycle and the carbon-carbon double in the structure of the probe bond served as the viscosity response site. Finally, the probe HT-Bzh was screened as the optimal mitochondrial viscosity probe according to its responsiveness, targeting, and interference resistance. The fluorescence intensity of the probe HT-Bzh increased 22-fold when the viscosity was increased from 13.75 to 811.2 cP. In summary, all four viscosity probes we have developed can be used in different applications depending on the external environment, providing a valuable reference for the design of potential tools to address viscosity monitoring in biological systems.

Carbazole-based mitochondria-targeted fluorescent probes for in vivo viscosity and cyanide detection in cells and zebrafish

Cells of most eukaryotic species contain mitochondria, which play a role in physiological processes such as cellular senescence, metabolism, and autophagy. Viscosity is considered a key marker for many illnesses and is involved in several crucial physiological processes. Cyanide (CN-) can target cytochrome-c oxidase, disrupting the mitochondrial electron transport chain and causing cell death through asphyxiation. In this study, a fluorescent probe named HL-1, which targets mitochondria and measures viscosity and CN- levels, was designed and synthesized. HL-1 is viscosity-sensitive, with a linear correlation coefficient of up to 0.992. In addition, HL-1 was found to change color substantially during a nucleophilic addition reaction with CN-, which has a low detection limit of 47 nM. HL-1 not only detects viscosity and exogenous CN- in SKOV-3 cells and zebrafish but also monitors viscosity changes during mitochondrial autophagy in real time. Furthermore, HL-1 has been used successfully to monitor changes in mitochondrial membrane potential during apoptosis. Endogenous CN- in plant samples was quantified. HL-1 provides new ideas for studying viscosity and CN-.