Protein Adsorption and Its Effects on Electroanalytical Performance of Nanocellulose/Carbon Nanotube Composite Electrodes

Protein fouling is a critical issue in the developmentof electrochemicalsensors for medical applications, as it can significantly impact theirsensitivity, stability, and reliability. Modifying planar electrodeswith conductive nanomaterials that possess a high surface area, suchas carbon nanotubes (CNTs), has been shown to significantly improvefouling resistance and sensitivity. However, the inherent hydrophobicityof CNTs and their poor dispersibility in solvents pose challengesin optimizing such electrode architectures for maximum sensitivity.Fortunately, nanocellulosic materials offer an efficient and sustainableapproach to achieving effective functional and hybrid nanoscale architecturesby enabling stable aqueous dispersions of carbon nanomaterials. Additionally,the inherent hygroscopicity and fouling-resistant nature of nanocellulosicmaterials can provide superior functionalities in such composites.In this study, we evaluate the fouling behavior of two nanocellulose(NC)/multiwalled carbon nanotube (MWCNT) composite electrode systems:one using sulfated cellulose nanofibers and another using sulfatedcellulose nanocrystals. We compare these composites to commercialMWCNT electrodes without nanocellulose and analyze their behaviorin physiologically relevant fouling environments of varying complexityusing common outer- and inner-sphere redox probes. Additionally, weuse quartz crystal microgravimetry with dissipation monitoring (QCM-D)to investigate the behavior of amorphous carbon surfaces and nanocellulosicmaterials in fouling environments. Our results demonstrate that theNC/MWCNT composite electrodes provide significant advantages for measurementreliability, sensitivity, and selectivity over only MWCNT-based electrodes,even in complex physiological monitoring environments such as humanplasma.