Fig. 6.

Enhanced sensitivity for MB-DNA reduction upon electrocatalytic signal amplification. Electrodes were incubated with 20 μL of MB-DNA of varying concentrations, ranging from 25 μM down to 250 pM, resulting in the electrodes being exposed to 500 pmol down to 5 fmol of MB-DNA during monolayer formation. The surfaces were thoroughly washed and backfilled with mercaptohexanol prior to measurement. Scans were performed in phosphate buffer (5 mM phosphate, 5 mM NaCl, 40 mM MgCl₂, 5 mM spermidine, and pH 7) with and without hemoglobin (25 μM). The reduction of MB-DNA was quantified from the reductive peak area in the CV (black), without hemoglobin, and the accumulated charge after 10 s in the chronocoulometry (red), with hemoglobin.