Cathodic detection of H₂O₂ based on nanopyramidal gold surface with enhanced electron transfer of myoglobin

Direct and reversible electron transfer of myoglobin (Mb), for the first time, is achieved at nanopyramidal gold surface, which was fabricated by one-step electrodeposition, with redox formal potential of 0.21 ± 0.01 V (vs. Ag/AgCl) and an apparent heterogeneous electron-transfer rate constant (k_s) of 1.6 ± 0.2 s^-1. Electrochemical investigation indicates that Mb is stably confined on the nanopyramidal gold surface and maintains electrocatalytic activity toward hydrogen peroxide (H₂O₂). The facilitated electron transfer combined with the intrinsic catalytical activity of Mb substantially construct the third-generation biosensor for H₂O₂. The positive redox potential of Mb at the nanostructured gold electrode gives a strong basis for determination of H₂O₂ with high selectivity. Besides this advantage, the present biosensor also exhibits quick response time, broad linear range, and good sensitivity. The dynamic detection linear range is from 1 μM to 1.4 mM with a detection limit of 0.5 μM at 3σ. The striking analytical performance of the present biosensor, as well as the biocompatibility of gold nanostructures provided a potential for continuous, on-line detection of H₂O₂ in the biological system.