Hydrogel-modified graphene electrode for electrochemical sensing

This thesis investigated hydrogel-coated graphene electrodes for stable and sensitive electrochemical detection, with the final focus on resazurin (RZ) as a redox probe for the detection of living bacterial cells in solutions. Different hydrogels were fabricated via inkjet printing on graphene electrodes, where drop-on-demand inkjet printing of various hydrogel co-monomers in different ratios and in combination with in-line photopolymerization enabled controlled modification of the also inkjet printed graphene electrode surface. To support data analysis, a custom-made, Python-based program with an interactive user interface was developed. The electrochemical performance of the graphene electrodes was first benchmarked against glassy carbon using a standard electro-active species, which was ferrocenemethanol (FcMeOH), followed by the evaluation of the hydrogel-coated graphene electrodes. The hydrogel composition was found to influence diffusion, adsorption and in general the sensing sensitivity. Subsequently, RZ was employed to study the electrode behavior for the detection of living bacterial cells. The impact of the various hydrogel coatings on signal stability was systematically examined. Additionally, the loading capacity of both bare and hydrogel-coated electrodes for RZ was assessed, highlighting their potential as reagent pre-loaded sensing platforms for bacteria detection. Finally, the accessibility and utilization of RZ pre-loaded hydrogels were validated through incubation with living bacterial cell cultures, confirming its applicability as electrochemical bacteria sensing platforms based on microbial activity detection.