In situ enzymatic generation of gold for ultrasensitive amperometric sandwich immunoassay of procalcitonin

Procalcitonin (PCT) is an important indicator for bacterial inflammatory diseases, and its sensitive, accurate and rapid detection has important clinical value. On the basis of sandwich immunoassay, glucose oxidase-catalyzed gold deposition and in-situ microliter-droplet anodic stripping voltammetry (ASV) of the enzyme-generated gold directly on the immunoelectrode, the ultrasensitive electrochemical detection of PCT is achieved. A new method of the chemical dissolution of gold by an appropriately diluted aqua regia and the simultaneous cathodic preconcentration of gold on the immunoelectrode is suggested, which gives the better performance for the ASV analysis of gold than the reported one. Under optimized conditions, the ASV peak current is linear with the common logarithm of PCT concentration from 0.05 fg mL−1 to 500 ng mL−1, with a limit of detection (LOD, S/N = 3) as low as 0.04 fg mL−1. Our method has also been used for detection of PCT in serum samples with satisfactory results.