Design and Screening of Fluorescent Probes Based upon Hemicyanine Dyes to Sensitively Respond to HSO3- in Living Cells.

SO2, a gas signaling molecule, can be produced endogenously in mitochondria. Its hydrolysate, HSO3-, plays a key role in food preservation, cardiovascular relaxation, and other fields, suggesting that it is important to achieve its detection. Here, based on the Michael addition mechanism, four hemicyanine dye fluorescent probes (ETN, ETB, STB, and EIB) were designed and synthesized for responding to HSO3-. We evaluated the reaction ability of different probes with HSO3- and tried to explain the reasons for the significantly different response effects between probes and HSO3- according to the structure-activity relationship. The influence of different substituents of probes on the properties of mitochondria-targeting was also discussed. Finally, we screened out ETN as the optimal HSO3- probe due to its high sensitivity, rapid reactivity, and good mitochondria-targeting, and it could sensitively respond to HSO3- in living cells. The LODs of ETN for HSO3- were calculated by both absorption and fluorescence methods, respectively, which were 2.727 and 0.823 µM. Our work provided valuable references for designing strategies and potential tools for response to SO2 derivatives in biosystems.

Advances in the Functional Nucleic Acid Biosensors for Detection of Lead Ions.

Lead ions (Pb2+) are destructive to the natural environment and public health, so the efficient detection of Pb2+ is particularly important. Although the instrumental analysis methods have high accuracy, they require high cost and precise operation, which limits their wide application. Therefore, many strategies have been extensively studied for detecting Pb2+ by biosensors. Functional nucleic acids have become an efficient tool in this field. This review focuses on the recent biosensors of detecting Pb2+ based on functional nucleic acids from 2010 to 2020, in which DNAzyme, DNA G-quadruplex and aptamer will be introduced. The biosensors are divided into three categories that colorimetric, fluorometric and electrochemical biosensors according to the different reported signals. The action mechanism and detection effect of each biosensor are explained. Finally, the present situation of nucleic acid biosensor for the detection of Pb2+ is summarized and the future research direction is prospected.

A cysteine and Hg2+ detection method based on transformation supramolecular assembly of cyanine dye by AGRO100.

ETC (3,3'-di(3-sulfopropyl)-4,5,4',5'-dibenzo-9-ethylthiacarbocyanine triethylammonium salt), as a derivative of thiazole, is capable of forming various aggregates by the short-range noncovalent interaction forces under specific conditions, accompanying with significant absorbance and fluorescence characteristics. In this work, a label-free probe (ETC) for the detection of Cys (Cysteine) and Hg2+ was developed based on transformation between monomers and J-aggregations by AGRO100. AGRO100 can transform between single-stranded DNA and G-quadruplex to realize recognition of Cys and Hg2+ in dual-channel mode. These recognitional signals can be captured by UV-visible absorption spectra and fluorescence spectroscopy. ETC exhibits high sensitivity and selectivity with the detection limit of 0.197 nM in a wide range of 0-15 µM, which can apply of Cys and Hg2+ detection in human serum.