Effect of Various Carbon Electrodes on MIP-Based Sensing Proteins Using Poly(Scopoletin): A Case Study of Ferritin

Sensitivity in the sub-nanomolar concentration region is required to determine important protein biomarkers, e.g., ferritin. As a prerequisite for high sensitivity, in this paper, the affinity of the functional monomer to the macromolecular target ferritin in solution was compared with the value for the respective molecularly imprinted polymer (MIP)-based electrodes, and the influence of various surface modifications of the electrode was investigated. The analytical performance of ferritin sensing was investigated using three different carbon electrodes (screen-printed carbon electrodes, single-walled-carbon-nanotube-modified screen-printed carbon electrodes, and glassy carbon electrodes) covered with a scopoletin-based MIP layer. Regardless of the electrode type, the template molecule ferritin was mixed with the functional monomer scopoletin, and electropolymerization was conducted using multistep amperometry. All stages of MIP preparation were followed by evaluating the diffusional permeability of the redox marker ferricyanide/ferrocyanide through the polymer layer by differential pulse voltammetry. The best results were obtained with glassy carbon electrodes. The MIP sensor responded up to 0.5 µM linearly with a K_d of 0.30 µM. Similar results were also obtained in solution upon the interaction of scopoletin and ferritin using fluorescence spectroscopy, resulting in the quenching of the scopoletin signal, with a calculated K_d of 0.81 µM. Moreover, the binding of 1 µM ferritin led to 49.6% suppression, whereas human serum albumin caused 8.6% suppression.