Fig. 2. Effect of REEs on bioelectrocatalytic performance of NAD⁺-dependent GDH. (a) Amperometric current responses of the GDH-based biosensor toward titrations of 10 and 20 μM glutamate at 0.0 V vs. Ag/AgCl in aCSF containing 2 mM NAD⁺ in the absence or presence of 16 μM Yb³⁺, La³⁺ or Eu³⁺. (b) Relative sensitivity of the GDH-based glutamate biosensor.