A highly selective and sensitive boronic acid-based sensor for detecting Pd2+ ion under mild conditions

A Prompt Study on Recent Advances in the Development Of Colorimetric and Fluorescent Chemosensors for "Nanomolar Detection" of Biologically Important Analytes

Fluorescent and colorimetric chemosensors for selective detection of various biologically important analytes have been widely applied in different areas such as biology, physiology, pharmacology, and environmental sciences. The research area based on fluorescent chemosensors has been in existence for about 150 years with the development of large number of fluorescent chemosensors for selective detection of cations as metal ions, anions, reactive species, neutral molecules and different gases etc. Despite the progress made in this field, several problems and challenges still exist. The most important part of sensing is limit of detection (LOD) which is the lowest concentration that can be measured (detected) with statistical significance by means of a given analytical procedure. Although there are so many reports available for detection of millimolar to micromolar range but the development of chemosensors for the detection of analytes in nanomolar range is still a challenging task. Therefore, in our current review we have focused the history and a general overview of the development in the research of fluorescent sensors for selective detection of various analytes at nanomolar level only. The basic principles involved in the design of chemosensors for specific analytes, binding mode, photophysical properties and various directions are also covered here. Summary of physiochemical properties, mechanistic view and type of different chemosensors has been demonstrated concisely in the tabular forms.

Novel detection method for gallic acid: A water soluble boronic acid-based fluorescent sensor with double recognition sites

As one of the widespread phenols in nature, gallic acid (GA) has attracted a subject of attention due to its extensive biological properties. It is very important and significant to develop a sensitive and selective gallic acid sensor. In recent years, owing to their reversible covalent binding with Lewis bases and polyols, boronic acid compounds have been widely reported as fluorescence sensors for the identification of carbohydrates, ions and hydrogen peroxide, etc. However, boronic acid sensors for specific recognition of gallic acid have not been reported. Herein, a novel water-soluble boronic acid sensor with double recognition sites is reported. When the concentration of gallic acid added was 1.1 × 10^-4 M, the fluorescence intensity of sensor 9b decreased by 80%, followed by pyrogallic acid and dopamine. However, the fluorescence of the sensor 9b combined with other analytes such as ATP, sialic acid, and uridine was basically unchanged, indicating that the sensor 9b had no ability to recognize these analytes. Also, sensor 9b has a fast response time to gallic acid at room temperature, and has a high binding constant (12355.9 ± 156.89 M^-1) and low LOD (7.30 × 10^-7 M). Moreover, gallic acid content of real samples was also determined, and the results showed that this method has a higher recovery rate. Therefore, sensor 9b can be used as a potential tool for detecting biologically significant gallic acid in actual samples such as food, medicine, and environmental analysis samples.

A near-infrared, colorimetric and ratiometric fluorescent sensor with high sensitivity to hydrogen peroxide and viscosity for solutions detection and imaging living cells

Considering to the importance of hydrogen peroxide (H₂O₂) in a number of pathological processes and fluorescence sensor as a powerful tool for imaging and therapy of H₂O₂-related diseases, herein, a near-infrared fluorescent sensor for colorimetric and ratiometric detecting H₂O₂ and viscosity, named NCR, was constructed and reported. Its long emission wavelength (670 nm) avoids the interference of biological autofluorescence. When NCR interacted with 10 equiv. of H₂O₂, colorimetric characteristic provides a clear naked eye recognition (colourless turned to green under UV light and light purple turned to colorless under visible light). In addition, NCR shows high sensitivity to viscosity with or without the addition of H₂O₂. It was also found alkaline environment contribute to enhance fluorescence response to H₂O₂. A suitable water-octanol partition coefficient (logP, 0.521 ± 0.003) and low cytotoxicity displayed that NCR is very favorable to image living cells. Furthermore, exogenous and endogenous H₂O₂ was detected successfully by NCR in living Hela cells. These studies indicate that NCR has great potential to develop as a practical tool for monitoring H₂O₂ level in biological process.