Electrochemical modification and analytical exploration of resazurin as a redox-active probe for electrochemical biosensors

• Electrochemical modification of resazurin into resorufin/dihydro resorufin (RR/DRR) as redox electrode catalyst. • Surface-confined redox process exhibits good potentiodynamic stability, and pH-dependency has significance in bio-electro catalysis. • Highly selective reduction of H 2 O 2 at low working potential. • Demonstrated glucose biosensor for direct detection of high concentrations of glucose. An electrochemical potential-assisted functionalization strategy is used to immobilize resazurin (AZ) on multiwalled carbon nanotube surfaces in a physiological buffer leading to the formation of a resorufin/dihydro resorufin (RR/DRR) redox couple. The electrochemical characterizations that reveal the modified surface are surface-confined behavior with an electron transfer rate constant of 4.4 s −1 . Thus modified RR/DRR redox couple was found to modulate the interfacial characteristics to the benefits of bio-electrocatalysis since the redox molecule has sensitivity to pH, negative redox potential, and selectivity to analytes. The hydrogen peroxide (H 2 O 2 ) reduction and sensing performance of the AZ-modified electrode surface were evaluated. The experimental results revealed the direct detection of high concentrations of H 2 O 2 at the electrified interface before the oxygen reduction potential. Furthermore, the designed sensor exhibited high selectivity for H 2 O 2 even in the presence of interfering molecules in the solution. In addition, for the demonstration, the glucose oxidase enzymes were immobilized on carbon nanotubes modified with an RR/DRR redox couple, and the electron tunneling behavior was investigated. The developed sensor could be used for the reagent-less electrochemical biosensing of glucose up to 30 mM. Thus, the AZ-based redox electrode catalysts can be applied in diverse biosensor applications.