Employing electrochemically derived pH gradients for Lab-on-PCB protein preconcentration implementations

Abstract

Abstract Protein preconcentration is an essential sample preparation step when analysing samples where the targeted proteins are in low concentrations, such as bodily fluids as well as water or wastewater. Nonetheless, very few practical implementations of miniaturized protein pre-concentration devices have been demonstrated in practice and even fewer in integration with other microanalytical steps. In this paper we propose for the first time a miniaturized isoelectric focusing-based protein-preconcentration device based on electrochemically derived pH gradients, rather than existing chemical reagent approaches. That way we are reducing the need for additional chemical reagents to zero, whilst enabling the device incorporation in a seamlessly integrated full protein analysis microsystem via Lab-on-PCB technology. We apply our previously presented Lab-on-PCB approach to quantitatively control the pH of a solution at the vicinity of planar electrodes using the electrochemical generation of acid through redox-active self-assembled monolayers. The presented device was comprised of a printed circuit board with an array of gold electrodes which was functionalised with 4-Aminothiophenol; this formed a self-assembled monolayer which was electropolymerised to improve its electrochemical reversibility. Protein preconcentration was performed in two configurations, one of which was open and required the use of a holder to suspend a well of fluid above the electrodes, and another which used microfluidic channels to enclose small volumes of fluid. Reported here is the data for protein preconcentration in both these forms with a quantitative concentration factor shown for the open form and qualitative proof shown for the microfluidic.