Cellulose nanocrystals decorated with gold nanoparticles immobilizing GOx enzyme for non-invasive biosensing of human salivary glucose

A cellulose nanocrystal (CNCs) material was converted into its dialdehyde before being decorated with gold nanoparticles (AuNPs) through an aminothiophenol linker. Then GOx enzyme was immobilized onto the CNCs-AuNPs using thioctic acid (TA) as a double linker. The prepared materials were characterized using morphological (SPM & SEM), spectroscopic (UV-visible & FTIR) and electrochemical (CV & EIS) techniques. The developed GOx-TA-AuNPs-CNC material loaded onto a GCE offered a convenient platform for developing a non-invasive enzymatic glucose biosensor for monitoring glucose in human saliva. The designed biosensor demonstrated good analytical performance for glucose sensing using CV with LR = 0.1-1.6 mM, R² = 0.9925, and LOD = 40 μM under physiological pH conditions. The developed biosensor possessed high selectivity towards glucose in the presence of common glucose interferents such as AA, UA and DA. The salivary glucose was measured and correlated with the value of serum glucose of a sample from the same person.