Ultrasensitive Detection of Hydrogen Peroxide Using Methylene Blue Grafted on Molecular Wires as Nanozyme with Catalase-like Activity.

In this study, we present the development of an electrochemical sensor designed for ultrasensitive detection of endogenous H 2 O 2 . This sensor relies on signal amplification achieved through nanozyme activity exhibited by methylene blue (MB) grafted onto a peptide support. The sensor exhibited excellent selectivity and sensitivity, with a limit of detection of 18 nM and a linear detection range of 20-200 nM. Thus, we have validated the concept of the MB-peptide system, serving as both an electroactive label and a catalyst for H 2 O 2 decomposition under electrochemical conditions. The implemented signal amplification system enables the rapid detection of H 2 O 2 , with an overall assay time of 1-2 min, a significant improvement compared to amperometric detection using surface-immobilized enzymes.