(Left) Original and (right) background subtracted voltammograms recorded at CDH variant (A-B) E501C, (C-D) T680C, (E-F) E653C and (G-H) D792C modified GC/MWCNT electrodes, in argon-saturated 50 mM acetate buffer (pH 5.5), containing 30 mM CaCl2, 1 mM ferrocenecarboxylic acid and different concentrations of D-glucose from 0 to 300 mM. The potential was swept at 2 mV/s.