Exploring the electrochemical behaviour of digestive enzymes at a liquid|liquid micro-interface array

Trypsin and pepsin are proteolytic enzymes secreted by the digestive system to digest proteins. Here, we examine the electrochemical behaviour and detection of trypsin and pepsin at a liquid/liquid (L|L) micro-interface array. For both proteins, aqueous phase of 10 mM hydrochloric acid was the only electrolyte solution in which they were electroactive. Neither protein was detected below 30 μM by cyclic voltammetry (CV) but stripping voltammetry following adsorption (AdSV) enabled the detection of sub-micromolar concentrations of both proteins. Although pepsin was electroactive at the micro-interface array in aqueous phase of 10 mM HCl, its behaviour was ill-defined and unsuitable for characterization by CV. It was found that pepsin easily blocked the micro-interfaces, as seen by greatly hampered ion transfer voltammetry of tetrapropylammonium ion (TPrA⁺) whereas trypsin only slightly impeded TPrA⁺ transfer. This highlights the dissimilarity between pepsin and trypsin. These results illustrate the rich viability of electrochemistry at L|L micro-interface arrays as a tool to explore the behaviour and detection of biological macromolecules.