Study of Factors Affecting Molecular Behaviors in Phenothiazine-Mediated Biosensing by Electrochemical and Spectroscopic Methods

Reagentless glucose-detecting biosensors were constructed by incorporating a series of phenothiazine derivatives as mediators onto chitosan (CHIT) matrix via different covalent bonds, wherein glucose oxidase (GOx) was employed as the enzyme. Electrochemical studies show significant decrease in the electrocatalytic current during cyclic voltammetric and amperometric measurements, resulting from complexes formation between GOx and phenothiazine molecules. This behavior was further verified by spectroscopic studies. The decrease in the peak intensity at 258 nm is due to the gradual complexes formation over time, consistent to the decrease in the current signal in electrochemical investigations. Correlation with the molecular structures of phenothiazine derivatives reveals a strong relationship between the hydrophobicity of the mediators and the stability of the biosensor electrodes.