Abstract
Non-enzymatic saccharide sensors are of great interest in diagnostics, but their non-selectivity limits their practical diagnostic abilities. In this study, we investigated the electrochemical oxidation of monosaccharides at nanoporous gold (NPG) catalysts with different contributions of surface crystallographic orientations. Fructose elicited no clear electrochemical response, but glucose, galactose, and mannose produced clear oxidative current. The onset potentials for oxidation of these saccharides depended on the surface atomic structure of the NPG. The oxidation potential was approximately 100 mV less positive at the Au(100)-enhanced NPG than at the Au(111)-enhanced NPG. Furthermore, the voltammetric responses significantly differed among the saccharides. Galactose was oxidized at less positive potential and exhibited a higher current response than the other saccharides. This tendency was enhanced in the presence of chloride ions. These features enabled the selective and sensitive detection of galactose at an NPG electrode without enzymes under physiological conditions. A linear range of 10 μM to 1.8 mM was obtained in the calibration plot, which was comparable to those in previously reported enzymatic galactose sensors. Thus, we demonstrated that controlling the crystallographic orientation on the nanostructured electrode surface is useful in developing electrochemical sensors.
Highlights
Occurring sugars such as glucose and galactose are involved in many biological processes.The accurate detection of these monosaccharides is critically important in clinical chemistry, food science, human nutrition, and fermentation industries [1,2]
We examined the electrochemical oxidation of monosaccharides at two kinds of nanoporous gold (NPG) with different compositions of surface crystallographic orientations, and found that their oxidation behaviors depended on the surface atomic structure
We reported that NPG electrodes prepared from solutions of 35 and 500 mM HCl (NPG-35 and NPG-500) exhibit different contributions of surface atomic structure and crystallographic orientation [30]
Summary
Occurring sugars such as glucose and galactose are involved in many biological processes.The accurate detection of these monosaccharides is critically important in clinical chemistry, food science, human nutrition, and fermentation industries [1,2]. Occurring sugars such as glucose and galactose are involved in many biological processes. Diabetes mellitus is a chronic and serious disease caused by disorders in carbohydrate metabolism, and characterized by abnormally high blood glucose levels. Determining glucose level is important for the diagnosis and treatment of diabetes. Elevated galactose levels are symptomatic of certain diseases such as galactosemia, galactosuria, and other metabolic disorders [3,4]. Galactosemia is a genetically inherited metabolic disorder caused by the absence of enzyme involved in galactose metabolism. This disease is normally treated by restricting dietary galactose. For neonates less than 5 days old, if the galactose concentration in the blood exceeds 1.11 mM, galactosemia can be fatal [6].
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