Aluminum-Doped Zinc Oxide Enzymatic Dopamine Biosensor Integrated With Potentiometric Readout Circuit Board

In this study, the standard industrial flexible printed circuit board (FPCB) was employed to fabricate the potentiometric enzymatic dopamine (DA) biosensor. The aluminum-doped zinc oxide (AZO) was used to make the sensing films of the DA sensor. This sensing film was prepared by a radio frequency (RF) sputtering system. The thickness and surface morphology of the AZO films were observed by the field emission scanning electron microscope (FE-SEM), and the elemental composition and oxidation state of the films were analyzed through X-ray electron spectroscopy (XPS). Tyrosinase (Tyr) was used as the enzyme of the sensor, which was immobilized on AZO film with (3-Aminopropyl)triethoxysilane (APTES) and glutaraldehyde. After the sensor was prepared, we integrated the sensor and the readout circuit board through the FPCB connecter and then measured the sensing characteristics of the DA sensor in the DA concentration range of
$1~\mu \text{M}$
–10 mM. The sensing characteristics mostly include average sensitivity and linearity, limit of detection (LOD), interference effect, response time, reproducibility, flexibility, and lifetime. Based on the experimental results, the DA sensor in this study has good sensing characteristics. Through the enzyme, the sensor has good selectivity for DA in the presence of other relatively high concentrations interfered with biomolecules.