Antioxidant Biosensor based on Deinococcus radiodurans Biofilm immobilized on Screen-printed Carbon Electrode (SPCE) Surface

Antioxidant biosensor based on D. radiodurans biofilm has been investigated in this research. The biofilm producing SOD enzymes were immobilized on SPCE surface. Optimization of experimental measurements were carried out by the response surface method. The optimum value obtained was at the buffer pH 7, suspension pH 6, and optical density (OD) 0.5. The morphology of SPCE surfaces was characterized by SEM. The optimum result was used to determinate analytical performance, including linearity, sensitivity, limit of detection (LOD), limit of quantity (LOQ), precision, selectivity, stability, and repeatability. Linearity was achieved in the xanthine concentration range of 0.1–0.6 mM with the equation y = 40.79x + 57.173 and R² = 0.99. The apparent Michaelis-Menten constant KM was evaluated. It was found that the biosensor had a low KM of 40 μM. LOD and LOQ respectively 40.8 μM and 123.7 μM with sensitivity 40.79 μA mM-1. Precision showed that RSD was less than 5%. Stability was measured for 35 days and retained 90% of current for the period. Repeatability showed RSD ≤ 5%. The selectivity of this method still needs to increase. In conclusion, antioxidant biosensor based on D. radiodurans biofilm may be used to measure the capacity of antioxidant products practically.