The Synthesis Of New Selenium Fluorescent Probes And Its Application In The Detection Of Biologically Active Substances

Redox homeostasis is critical for proper cellular function. The reduction-oxidation state of the cell is primarily a consequence of the precise balance between the levels of reactive oxygen species (ROS) and reducing equivalents. Unregulated production of ROS results in potentially cytotoxic"oxidative stress". Many diseases (e.g., Alzheimer's disease) are linked with ROS damage as a result of an imbalance between radical-generating and radical-scavenging systems. Thus, the study of intracellular redox cycles has an important physiological and pathological significance.Peroxynitrite (ONOO~-), a powerful oxidizing agent formed from a diffusion-controlled reaction between NO and O2-·in cells, plays an important role in biological processes. Depending on concentration, ONOO~- can be either"friend"or"foe". A well-controlled level of ONOO~- drives important cellular functions such as keeping cellular integrity and organ homeostasis, whereas a high level of ONOO~- can induce DNA damage and initiate lipid peroxidation in biomembranes. Among the reported methods for detecting ONOO~-, the use of fluorescent probes had its apparent advantages over other methods. Furthermore, fluorescent probes that can respond reversibly to changes of ONOO~- concentration would be much more valuable for studying the generation, metabolism of ONOO~- and its dynamic damaging of living cells.Selenium, long known to be an important dietary"antioxidant", is now recognized as an essential component of the active sites of many enzymes. Moreover, depending on the redox cycling of selenium, many organoselenium compounds are capable of simulating catalytic functions demonstrated by natural enzymes. And one of the important biochemical functions of these compounds is the protection against ONOO~-. In 2000, Woznichak et al. reported that phenylaminoethyl selenides, which can be oxidized to the corresponding selenoxides by ONOO~-, play a protective role in the defense against ONOO~-, and the catalytic cycles can be exerted by using ascorbate as reducing equivalents. Although there is an increasing amount of evidence showing that selenium redox cycling can enhance the protective effects of organoselenium compounds against ONOO~-, integrating selenium into a fluorescent probe to detect ONOO~- and monitor the redox cycles in living cells has not been reported to date.Based on the reversible changes in spectrum characters of the organoselenium fluorescent probes reacting with ROS and bio-active molecules, we have designed and synthetized the novel reversible fluorescent probes. The probes were also applied to confocal imaging of bio-active molecules in living cells. We carried out one aspect of investigation:We report the synthesis and biological application of benzylselenide- tricarbocyanine (BzSe-Cy), a new near-infrared (NIR) organoselenium probe for selective detection of peroxynitrite (ONOO~-) and imaging redox cycles in living cells. Our strategy is to take advantage of protective effect of selenide against ONOO~- and the redox chemistry of selenium moiety to design a reversible fluorescent probe. BzSe-Cy features a reversible response to ONOO~- or reduced ascorbate (ASCH2) under physiological conditions, and exhibits good selectivity for ONOO~-. Fluorescence imaging experiments by confocal microscopy show that BzSe-Cy can be applied to the imaging of multiple cycles of oxidative stress and reductive repair RAW 264.7 cells and it exhibits low toxicity, good membrane permeability.