Electrochemical behaviour of myoglobin at an array of microscopic liquid–liquid interfaces

Abstract

Electrochemistry at liquid-liquid interfaces, or at interfaces between two immiscible electrolyte solutions (ITIES), provides a basis for the non-redox detection of biological molecules, based on iontransfer or adsorption processes. The electroactivity of myoglobin at an array of micron-sized liquidorganogel interfaces was investigated. The µITIES array was patterned with a silicon membrane consisting of an array of eight pores with radii of ~12.8 µm and a pore to pore separation of ~400 µm.Using cyclic voltammetry at the ITIES, the protein was shown to adsorb at the interface and facilitate the transfer of the organic phase electrolyte anions to the aqueous side of the interface. The electrochemical current response was linear with concentration in the range of 1 -6 µM, with corresponding surface coverage of 10 -50 pmol cm -2 . The reverse peak currents was found to be proportional to the voltammetric scan rate, indicating a desorption process. The detection of the protein was only possibly when the pH of the aqueous phase solution was below the pI of the protein. The steady-state simple ion transfer behaviour of tetraethylammonium cation was decreased on the forward sweep, providing a qualitative indication of the presence of adsorbed protein at the interface.Increasing the ionic strength of the aqueous phase resulted in enhanced peak currents, possibly due to aggregation of protein precipitates in the aqueous solution. UV/Vis absorbance spectroscopy was used 1 ISE Member.2 | P a g e to investigate the effects of various aqueous electrolyte solutions on the structure of the protein, and it was shown that at low pH the protein is at least partially denatured. These results provide the basis for label-free detection of myoglobin at the ITIES.

Voltammetry of proteins at liquid–liquid interfaces

“…A recent study 64 of the behaviour of myoglobin at a µITIES array indicated a similar detection capability as seen for HEWL and insulin, namely the achievement of 1 µM detection. Additionally, it was found that a single CV cycle resulted in the adsorption and desorption of an interfacial layer of the protein consistent with a coverage of 10-50 pmol cm -2 , assuming that the protein was fully protonated when in aqueous acidic (pH 2)…”

Ion‐Transfer Electrochemistry of Rat Amylin at the Water–Organogel Microinterface Array and Its Selective Detection in a Protein Mixture

“…The peak-shaped response on the reverse sweep is quite different to that in Figure 1 A and is consistent with thin-film or desorption behavior. [12,20] Figure 1 C shows that the ion-transfer current waves produced from a mixture of TEA + and amylin are still clearly identifiable as individual processes, indicating that there is no interference in the TEA + transfer process by the polypeptide in solution (and vice versa). However, there are no pre or post peaks on the forward scan voltammogram, which are usually present when products or reactants adsorb at an electrified interface.…”

Dynamic electrochemistry with ionophore based ion-selective membranes

“…10,[15][16][17][18][19][20][21][22] Both ohmic drop and capacitive currents are dramatically diminished utilizing these ultra-small liquidliquid interfaces. For instance, nanopipets, micro and nanofabrication are used to develop massive sensor arrays.…”