Determination of nitric oxide in biological samples

NO plays an important role in the regulation of physiological and pathophysiological mechanisms, and quite a lot of investigations have been focused on this kind of special molecule. It is difficult to achieve reliable ex vivo NO measurements with the existing analytical methods, and developing a reliable in vivo monitoring method for NO is still an urgent task. In this review, the techniques utilized for the determination of endogenous NO formed by enzymatic action and its reactions with other biological substances found in living organisms are discussed with respect to applications both in vivo or in vitro. In addition, various NO (micro)sensors and trap probes based on different principles are presented with their respective advantages and limitations. Finally, an NO monitoring system based on the combination of microdialysis sampling and chemiluminescence is introduced which is considered to be a prospective method for in vivo monitoring.