Use of Screen‐printed Electrodes Modified by Prussian Blue and Analogues in Sensing of Cysteine

The utilisation of screen‐printing technology allows for a mass scalable approach for the production of electrochemical screen‐printed electrodes (SPEs) and the presence of a redox mediator can add new possibilities to the electrochemical properties of the SPEs. Among the materials used as redox mediators, cyanidoferrates polymers can be used for electro‐oxidation of cysteine. In this work, two monomers, namely, Fe(CN)₆]⁴⁻ and Fe(CN)₅NH₃]³⁻ were used to produce Prussian blue (PB) and Prussian blue‐Ammine (PB‐Ammine), respectively. In addition, two modification methods were compared, firstly via a drop‐casting and secondly by the incorporation of these materials into a printable ink. The SPE modified by PB‐Ammine (drop‐casting) exhibits the highest electroactive area, however the highest heterogeneous rate constant was found with the SPE modified by PB‐Ammine that was incorporated into the ink. The highest value of the constant of electro‐oxidation of cysteine and lowest limit of detection was also observed in the SPE modified by PB incorporated into the ink. These studies suggest that the electrocatalytic properties of SPE modified by PB and PB‐Ammine are dependent upon the availability of Fe³⁺ catalytic sites and the increased kinetics of the chemical reaction between the catalytic sites and the analyte.