Hypochlorous acid (HOCl), a well-known universal disinfectant in clinical practice, plays important roles in immune systems of animal and human bodies. For understanding the roles of HOCl in living systems, a number of approaches, including chemiluminescence, colorimetric, electrochemical and chromatographic methods have been explored. For the detection of HOCl in live organisms, cutting-edge techniques, such as fluorescence/phosphorescence molecular probes, responsive nanoprobes, Raman and activatable photoacoustic sensors, have also been developed recently. In this review, the recent advances in the development of bioanalytical methods for detection of HOCl in environmental and biological specimens were summarized. More specifically, traditional techniques for assay of HOCl in bulk solution were initially discussed, and then fluorescence molecular probes, phosphorescence probes, responsive nanoprobes and other methods for HOCl detection were reviewed, which gives an overview of the developments and applications in bioanalytical methods for HOCl detection.

https://espace.library.uq.edu.au/view/UQ:709732/UQ709732_OA.pdf

Bioanalytical methods for hypochlorous acid detection: recent advances and challenges

Colorimetric and fluorometric detection of copper ion (Cu2+) has attracted much attention due to the biological, environmental and medical significance of the Cu2+ ion. Colorimetric and fluorescent detection of metal ions have proven to be powerful methods due to their simplicity, cost effectiveness, high detection limit and applicability to bioimaging. This review will consolidate selective and sensitive Cu2+ ion detection achieved by various receptor types in the years between 2013 to 2015.

Colorimetric and fluorescent chemosensors for Cu2+. A comprehensive review from the years 2013–15

Recent advances in the development of responsive probes for selective detection of cysteine

Environmental pollution has been a known threat to our world due to the rapid urbanization, changing lifestyle of people, and modern industrialization. Therefore, there is an urgent need to develop novel sensing approaches having promising performance with high reliability and sensitivity for the precise monitoring of various pollutants. Metal–organic frameworks (MOFs) have been intensively investigated by many researchers as electrode modifiers for electrochemical sensing due to their excellent properties and efficiency. Diverse MOF-based electrochemical sensing systems are applied for environmental analysis for the sensitive, rapid and cost-effective determination of various analytes because of their unique structures, and properties, including the tunable pore size, high surface area, high catalytic activity, and high density of active sites. The aim of this review article is to evaluate the application of MOFs in the electrochemical sensing of environmental pollutants including heavy metal ions, pesticides, phenolic compounds, nitroaromatic compounds, antibiotics, nitrite, and hydrazine. Current limitations and future directions for the application of MOF-based electrochemical sensors for the detection of environmental pollutants are discussed.

Performance of metal-organic frameworks in the electrochemical sensing of environmental pollutants

Restriction of intramolecular motion (RIM) of rigid aromatic cores is the most universal mechanism so far that can successfully explain almost all AIE/AIEEgenic systems. By designing two novel naphthalimide derivatives (NIB and NIBD), we experimentally demonstrated the effect of a single formyl group that can efficiently transform an aggregation caused quenching (ACQ) system (NIB) into an AIEEgenic system (NIBD) by strengthening the RIM process. Besides, the newly designed naphthalimide AIEEgen (NIBD) accomplished ultrasensitive detection of hydrazine at the parts per trillion level (LOD/81 ppt) in aqueous media with high selectivity and enormous improvement over the existing state of the art. An exceptional sensitivity is also achieved in the vapor phase (LOD/0.003%) using a Whatman paper strip based portable device for simple and cost-effective on-site detection. The detection mechanism involved a reaction-based spontaneous formation of a non-fluorescent hydrazone Schiff base derivative (NIBDH). The in vitro potentiality of the AIEEgenic probe was also demonstrated in two mammalian cell lines i.e. HeLa (human cervical cancer cell line) and HEK293T (Human embryonic kidney cell line that expresses a mutant version of the SV40 large T antigen). Owing to the highly selective formation of the hydrazone Schiff base complex with hydrazine, NIBD responds to the existence of hydrazine in both these cell lines without any interference from other biologically rich metal ions and amino acids. These outcomes could initiate a much wider use of formyl group induced condensed state emission and a key hypothesis that could generate newer avenues for ACQ to AIEE transformations for several practical applications including hydrazone Schiff base complexation for probing and manipulating hydrazine biology associated with several metabolic activities.

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Aldehyde group driven aggregation-induced enhanced emission in naphthalimides and its application for ultradetection of hydrazine on multiple platforms

Hydrazine is a very important industrial chemical and exhibits high toxicity to human beings. Here we have constructed a novel ICT-based fluorescence sensor with a high selectivity and sensitivity, rapid detection, and huge color-change. We used the sensor for hydrazine determination in live cells and also in live fish, and manufactured dipsticks using our sensor. The sensing mechanism is well rationalized with the aid of TD-DFT (time-dependent density functional theory) calculations.

A new fluorescent and colorimetric sensor for hydrazine and its application in biological systems

A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

A novel “turn-on” thiooxofluorescein-based colorimetric and fluorescent sensor for Hg2+ and its application in living cells

A novel turn-on fluorescent sensor (PIPH) based on phenanthroimidazole derivatives was successfully designed and synthesized. The probe shows high selectivity and sensitivity towards OCl− with approximately 20-fold fluorescence enhancement at 415 nm and the detection limit was measured to be 0.58 μM. Then through NMR spectra and high-resolution mass spectrometry, it was confirmed that the phenylhydrazine group of PIPH was decomposed by OCl−. The fluorescence enhancement mechanism of the probe was further investigated by theoretical calculations. Finally, Hela cells were applied in cell imaging. It was proved that the probe has potential capacity to detect hypochlorite in vivo.

A new turn-on fluorescent probe towards hypochlorite in living cells

A novel fluorescent probe (AQDA) based on quinizarin is designed and synthesized. Owing to a nucleophilic addition and a specific intramolecular cyclization reaction, the probe displays high selectivity towards cysteine (Cys) relative to other natural amino acids. The maximum fluorescent intensity is 30-fold that of the initial value in the presence of 5.0 equiv. Cys, and its detection limit is 0.158 μM. The recognition mechanism is further confirmed through mass spectroscopy and proton nuclear magnetic resonance titration. Simultaneously, the fluorescence enhancement mechanism is characterized by theoretical calculations, and experimental data are consistent with the theoretical results. Finally, the cellular imaging experiment verifies that AQDA possesses the capacity to detect endogenous Cys in living cells.

/pdf/a-simple-colorimetric-and-fluorescent-probe-with-high-4gy2tnmuow.pdf

Jing Guo

Papers

A new fluorescent and colorimetric sensor for hydrazine and its application in biological systems

A novel reaction-based colorimetric and ratiometric fluorescent sensor for cyanide anion with a large emission shift and high selectivity.

A novel “turn-on” thiooxofluorescein-based colorimetric and fluorescent sensor for Hg2+ and its application in living cells

A new turn-on fluorescent probe towards hypochlorite in living cells

A simple colorimetric and fluorescent probe with high selectivity towards cysteine over homocysteine and glutathione