A Single-Step Enzyme-Free Electrochemical Assay of N-acetyl-D-neuraminic Acid

N-acetyl-D-neuraminic acid (Neu5Ac) is a sialic acid endogenously produced in higher vertebrates including humans. Its significant physiological, nutritional and clinical importance have been revealed over the past decades and recently European Commission has approved its regulatory inclusion as a nutrition additive in commercial food products. Therefore, assay of Neu5Ac in various types of samples has potential interest. However, the state of the art of Neu5Ac assay is suffering from complex-multistep methods, costly biochemicals, sophisticated expensive instruments or long analysis time. This work presents a proof of concept for developing a single-step, robust and economic electrochemical method based on a chemoreceptor viz. ferroceneboronic acid (FcBA) for rapid assay of Neu5Ac in the linear dynamic range 0.1-5.5 mM with a limit of detection up to 30 & mu;M avoiding interference from other saccharides. Density functional theory calculations provided a valuable insight into the most thermodynamically stable geometry of the FcBA-Neu5Ac complex and its higher stability relative to the corresponding FcBA complexes of diol viz. glucose and & alpha;-hydroxy acid viz. lactic acid.