Application of alginate protective layers for screen-printed carbon electrodes (SPCE)

Bioelectrodes are widely used in electrochemical sensing for environmental monitoring and glucose detection, offering high specificity through enzyme-based recognition systems (Tsai et al., 2021; Mross et al., 2015; George et al., 2022). However, enzymes are sensitive to thermal degradation and interference from complex sample matrices, which can reduce sensor reliability (Wang et al., 2016; Campuzano et al., 2019). Protective coatings such as Nafion, alginate, chitosan, and polyurethane are used to reduce biofouling and surface contamination (Trouillon et al., 2009; Zhang et al., 2019; Hlavatá et al., 2014; Yu et al., 2006), but may also limit mass transport. This work proposes transient coatings that detach during operation, improving protection during storage while preserving sensing efficiency. Alginate is highlighted for its biocompatibility and gel-forming properties.

In this study, commercial screen-printed carbon electrodes were modified with alginate using two deposition methods: drop-casting and electrodeposition. For drop-casting, alginate solution was applied directly onto the working electrode, followed by CaCO₃ addition. In electrodeposition, a current of 150 mA was applied for 60 seconds while the electrode was immersed in an alginate/CaCO₃ solution. The modified electrodes were characterized using Infrared Reflection-Absorption Spectroscopy (IRRAS) and cyclic voltammetry (CV). CV analysis with [Fe(CN)₆]³⁻/⁴⁻ showed a slight decrease in oxidation current for drop-cast electrodes and an even smaller change for electrodeposited films, while maintaining similar voltammetric profiles, indicating preserved electrochemical behavior. Blank measurements confirmed that alginate is electrochemically inactive. IRRAS confirmed successful coating in both methods, with stronger signals for drop-casting than electrodeposition. After PBS washing, IRRAS signals largely disappeared, showing that the alginate layer can be removed and the electrode surface regenerated. This was confirmed by the full recovery of redox peaks in CV. Overall, alginate is a biocompatible, removable protective coating, and optimization of electrodeposition parameters could further improve performance for biosensor storage and antifouling applications.