Glucose biosensor based on a flexible Au/ZnO film to enhance the glucose oxidase catalytic response

Abstract

• The indirect isoelectric effect boosts the glucose oxidase immobilization. • The flexible electrode is mechanically stable. • Biosensor performance toward glucose detection is improved by ZnO thin film. • The bioelectrode shows high sensibility and low LOD and LOQ. • The area covered by ZnO shows higher current density toward glucose oxidation. The present work shows the influence of the isoelectric indirect effect of the semiconductor ZnO in the enzymatic immobilization in a glucose biosensor. For this purpose, thin films based on Au and Au/ZnO were synthesized on a microstructured flexible substrate of polyamide filter membrane (P.F) and characterized by FESEM and XRD. Both flexible surfaces were used to immobilize glucose oxidase (GOx) enzyme mixed with ferrocene methanol (Fc) and multiwalled carbon nanotubes (GOx-Fc/MWCNT). Subsequently, these surfaces were used as working electrodes to be evaluated as glucose biosensors. The effect of the ZnO film was compared. The performance of the flexible substrate based on Au/GOx-Fc/MWCNT and Au/ZnO/GOx-Fc/MWCNT as glucose sensor showed similar linearity between 0 – 12 mM glucose; however a higher sensitivity (30.00 µA mM -1 cm -2 ) and lower limit of detection and quantification values were obtained (0.25 mM and 0.83 mM, respectively) when ZnO thin film was used. The results suggest that the ZnO thin film in junction with GOx enzyme enhance the immobilization process of the biocatalyst, resulting in an improvement of the glucose biosensor parameters.