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Impact of a Surfactant on the Electroactivity of Proteins at an Aqueous–Organogel Microinterface Array

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journal contribution
posted on 05.02.2013, 00:00 authored by Shane O’Sullivan, Damien W. M. Arrigan
The impact of surfactant addition to the organic phase on the electroactivity of proteins at the aqueous–organogel interface was examined by voltammetry. The presence of bis­(2-ethylhexyl)­sulfosuccinate (AOT) in the organogel phase, as the sodium salt, caused marked changes in the peak currents for myoglobin detection. The protein desorption voltammetric peak exhibited a 6-fold increase in the current compared to the corresponding experiment without surfactant. Interfacial coverage showed a 17-fold increase in the adsorbed protein at the interface, from 50 pmol cm–2, in the absence of surfactant, to 850 pmol cm–2, in the presence of 10 mM surfactant. Additionally, the presence of the surfactant resulted in a second pair of adsorption/desorption peaks at lower potentials and in a change in the capacitance of the system. The formation of surfactant–protein and surfactant–protein–organic anion deposits is proposed on the basis of these features, leading to increased voltammetric signals for myoglobin, hemoglobin, and cytochrome c. The mechanism of protein–surfactant interaction was probed by using the surfactant as the anion in the organic phase electrolyte salt. Repetitive cyclic voltammetry of cytochrome c showed that in the presence of surfactant there was an enhancement of the signal, caused by a buildup of the protein–surfactant–electrolyte anion assembly at the interface. These findings provide the basis for surfactant-modified interfaces to enhance the electroanalytical performance for protein detection.