Surface Functionalization of Screen-Printed Carbon Electrodes for Electrochemical Biosensing in Equine Saliva

Abstract

Osteoarthritis (OA) is a progressive, long-term inflammatory condition that damages joint function and causes significant pain in both humans and animals. Many imaging techniques struggle to detect OA in its early stages, making early diagnosis challenging. A promising alternative is biomarker monitoring using electrochemical biosensors in saliva. The aim of this thesis is to investigate surface modification on screen-printed carbon electrodes as a model system for biosensor functionalization. The work focuses on establishing and evaluating a controlled surface chemistry using linker and passivation layers that mimic the immobilization strategy intended for future antibody-based sensing systems. Screen-printed carbon electrodes were functionalized using a PEG-based linker and click-chemistry-based surface modification. The surface immobilization was investigated using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), field-effect transistor (FET), and chronoamperometry (CA) measurements. Surface modification could be observed using CV, while EIS showed weaker but supporting trends. Transistor measurements showed slight trends, but additional measurements are needed to determine whether the observed changes were caused by surface modification. CA measurements showed no clear evidence of binding. Overall, these findings demonstrate that the investigated surface chemistry can be immobilized on screen-printed carbon electrodes and detected using electrochemical methods, providing a foundation for future biosensor design, where the next step is to introduce Fab’ fragments for biomarker binding. However, further optimization of both the surface modification and measurement setup is required.