A self-referencing microelectrode for real time measurements of silver flux

Silver has many diverse applications, including use as a biocide for biomedical devices and potable water systems. Increased use of silver has led to a demand for technologies which can measure dissolved species in situ. In addition to the development of tools such as electrodes for measuring dissolved silver concentration, techniques are needed which can quantify spatially and temporally dynamic transport of silver. For the first time, we demonstrate the use of a self-referencing Ag+-selective microelectrode for non-invasively quantifying Ag+ flux in biomedical and environmental applications. Characterization of sensor performance included detailed analysis of microelectrode sensitivity, selectivity, response time, limit of detection, and linear range. Liquid membrane microelectrode performance was similar to modern solid state electrodes, and in self-referencing modality differential signal acquisition was sufficient for use in a wide range of applications. Self-referencing microelectrodes were used to profile concentration boundary layer transport, providing a snapshot of microgradients in the unstirred boundary layer. In addition, time resolved, non-invasive measurements were used to quantify Ag+ release rate (efflux) from two common antimicrobial biomedical devices, and Ag+ uptake rate (influx) to a mature Pseudomonas aeruginosa biofilm during disinfection. Use of this technique will increase our understanding of silver transport in engineered antimicrobial devices and systems. In addition, the technique may be used to better our understanding of Ag+ release from nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.