Modification of a bioabsorbable carbon electrode on silk-fibroin carriers: setting the composition and adjustment of the working potential†

Abstract

In this work, different surface treatment and modification procedures (KCl, Na₂CO₃, H₂O₂, O₂ plasma, multi-walled carbon nanotubes (MWCNTs)) are applied to a screen-printed carbon-based electrode on bioabsorbable silk-fibroin, aiming to reduce the applied working potential in operation. The screen-printed carbon electrode houses the enzyme glucose oxidase for glucose monitoring, and is encapsulated by the biocompatible material Ecoflex. The working electrode is characterized amperometrically at different working potentials (0.6 to 1.2 V vs. the Ag/AgCl reference electrode) at physiological glucose concentrations ranging from 0.5 to 10 mM. The surface morphology of the electrode is analyzed utilizing scanning electron microscopy and contact angle measurements. Addition of 2 wt% MWCNTs to the carbon screen-printing paste allowed the reduction of the applied working potential from 1.2 to 0.8 V, resulting in a mean glucose sensitivity of 2.5 ± 0.6 μA cm⁻² mM⁻¹. Moreover, the bioabsorbability (i.e., the degradation behavior) of the different surface-treated carbon electrodes on silk-fibroin is studied over several months using the enzyme protease XIV from Streptomyces griseus.