Selenium- and Tellurium-Containing Fluorescent Molecular Probes for the Detection of Biologically Important Analytes

Abstract

As scientists in recent decades have discovered, selenium is an important trace element in life. The element is now known to play an important role in biology as an enzymatic antioxidant. In this case, it sits at the active site and converts biological hydrogen peroxides to water. Mimicking this reaction, chemists have synthesized several organoselenium compounds that undergo redox transformations. As such, these types of compounds are important in the future of both medicinal and materials chemistry. One main challenge for organochalcogen chemists has been to synthesize molecular probes that are soluble in water where a selenium or tellurium center can best modify electronics of the molecule based on a chemical oxidation or reduction event. In this Account, we discuss chemists' recent efforts to create chalcogen-based chemosensors through synthetic means and current photophysical understanding. Our work has focused on small chromophoric or fluorophoric molecules, in which we incorporate discrete organochalcogen atoms (e.g., R-Se-R, R-Te-R) in predesigned sites. These synthetic molecules, involving rational synthetic pathways, allow us to chemoselectively oxidize compounds and to study the level of analyte selectivity by way of their optical responses. All the reports we discussed here deal with well-defined and small synthetic molecular systems. With a large number of reports published over the last few years, many have notably originated from the laboratory of K. Han (P. R. China). This growing body of research has given chemists new ideas for the previously untenable reversible reactive oxygen species detection. While reversibility of the probe is technically important from the stand-point of the chalcogen center, facile regenerability of the probe using a secondary analyte to recover the initial probe is a very promising avenue. This is because (bio)chalcogen chemistry is extremely rich and bioinspired and continues to yield important developments across many scientific fields. Organochalcogen (R-E-R) chemistry in such chemical recognition and supramolecular pursuits is a fundamental tool to allow chemists to explore stable organic-based probe modalities of interest to develop better spectroscopic tools for (neuro)biological applications. Chalcogen donor sites also provide sites where metals can coordinate, and facile oxidation may extend to the sulfone analogues (R-EO2-R) or beyond. Consequently, chemists can then make use of reliable reversible chemical probing platforms based on the chemical redox properties valence state switching principally from 2 to 4 (and back to 2) of selenium and tellurium atoms. The main organic molecular skeletons have involved chemical frames including boron-dipyrromethene (BODIPY) systems, extended cyanine groups, naphthalimide, rhodamine, and fluorescein cores, and isoselenazolone, pyrene, coumarin, benzoselenadiazole, and selenoguanine systems. Our group has tested many such molecular probe systems in cellular milieu and under a series of conditions and competitive environment...

BODIPY‐Based Fluorescent Probes for Biothiols

“…Cells possess elaborate mechanisms to regulate their internal redox status. The intracellular redox homeostasis plays an essential role in maintaining cellular function and governs numerous essential biological processes and has broad implications in human health and disease . In this regard, the elucidation of the biological functions of intracellular redox changes between ROS and antioxidants, for example, biothiols, has become an important area of research.…”

“…The intracellular redox homeostasisp lays an essentialr olei nm aintaining cellular functiona nd governs numerous essential biological processes and has broad implications in human health and disease. [115,116] In this regard, the elucidationo ft he biological functions of intracellularr edox changes between ROS and antioxidants, for example, biothiols, has become an importanta rea of research. Recently,anumber of reaction-based fluorescent probesf or this redox cycle have been reported.…”

Imaging of Hypochlorous Acid by Fluorescence and Applications in Biological Systems

“…Ah igh number of novel heterocycles bearings ingle or multiple oxygen, sulfur,s elenium, or tellurium sites have been investigated over the years to help mimic redoxt ransformations which have involved ROS and biothiols. [39][40][41][42][43][44] These rationally designed synthetic molecules, provide ac hemoselectively oxidized (or reduced) compound towards hypochlorousacid and correlation in their optical responses. All reports discussed herein deal with well-defined and small synthetic molecular systems.…”

A new class of silica-supported chromo-fluorogenic chemosensors for anion recognition based on a selenourea scaffold

“…[1][2][3][4][5][6] A vast library of chemosensors has been proposed so far, but only recently organoselenium and organotellurium compounds have been used for this purpose. 7,8,9 Heavy chalcogen-containing derivatives, and in particular those containing selenium, are of great interest because selenium compounds play an important role as enzymatic antioxidants participating in the conversion of hydrogen peroxides in water in biological systems. 10 In the particular case of seleniumcontaining chemosensors, the formation of highly stable selenoxides is often the event that triggers the optical recognition of analytes such as reactive oxygen species (ROS) superoxide, 11 hypochlorite 12 or reactive nitrogen species (RNS, for instance peroxynitrate).…”