The electrochemical determination of NADH is of considerable interest because the NADH/NAD+ couple is the cofactor system for more than 300 dehydrogenase enzymatic reactions [1]. The dehydrogenase group is the largest one of the oxidoreductases enzymes that catalyze the oxidation of a variety of families, such as alcohols, that is of great interest from the analytical point of views [2]. However, the electrochemical determination of NADH at most of the unmodified metal and carbon surfaces suffers from the large overpotentials [3], which limit the selectivity of the detection in a real sample [4]. The present study describes the development of a very simple NADH biosensor based on the electrocatalytic activity of NiOx nanoparticles without using any redox mediator. To the best of our knowledge, this is the first report on the electrocatalytic activity of NiOx nanoparticles in the physiological pH. The deposition time of NiOx on the GC electrode is an efficient tool in the controlling of nanoparticles size and, hence, is a key factor in the success of construction of an efficient electrocatalytic surface.
