Fluorescence-based Nitric Oxide Detection

Abstract

A review. Over the past 15 years, multiple strategies for the development of NO biosensors were studied, ranging from electrochem. and EPR based techniques to those that make use of fluorescence spectroscopy. The advancement of the understanding of NO in biol. and the ability to design ever improving fluorescence-based sensors are remarkable considering the many challenges assocd. with handling and observing the elusive diat. gas, nitric oxide. Early research adapting the fluorescence-based nitrite sensor DAN for NO detection was only a beginning. This work ultimately led to development of the diaminofluorescein sensors and many other o-diamine-based sensors that are capable of detecting sub-mM NO levels in living cells. Unfortunately, these systems require O2 to react with NO to form a more reactive nitrosylating species such as N2O3. Other org.-based sensors such as dichlorofluorescin, the FNOCTs, and RBH were developed and studied for their NO-sensing abilities. All of these org. sensors, whether or not they react directly with NO, are incapable of reversibly binding and detecting nitric oxide. Some of the more recent successes in NO detection use transition metal ions. In these systems, the fluorescence emission properties of an attached fluorophore are altered upon treatment of the complex with NO. One successful strategy uses sGC or cytochrome c' labeled with a fluorescent reporter embedded in fiber optic probes, enabling reversible NO detection. Another route is to use small mol. transition metal complexes such as those of Katayama, the Co(II) complexes, and dirhodium tetracarboxylate complexes prepd. in the lab. These complexes are capable of detecting NO over a wide spatial field like the o-diamine-based sensors. but react with NO directly. The potential is great for further modification and development of small mol. transition metal complexes for studies in living cells capable of reversible, fast, and direct detection of NO by fluorescence methodologies. [on SciFinder (R)]