Large catalase based bioelectrode for biosensor application.

A large catalase (CAT) (Mr~90kDa), immobilized on multiwalled carbon nanotubes-Nafion(®) (MWCNT-NF) matrix and encapsulated with polyethylenimine (PEI) on glassy carbon electrode (GCE), showed a pair of nearly reversible cyclic voltammetric peaks for Fe((III))/Fe((II)) couple with formal potential of about -0.45V (vs. Ag/AgCl electrode at pH 7.5). PEI significantly reduced the charge transfer resistance and stabilized the bioelectrode through electrostatic interaction. The electron transfer rate constant and surface coverage of the immobilized CAT were 1.05±0.2s⁻¹ and 2.1×10⁻¹⁰ mol cm⁻², respectively. Studies on electrocatalytic activity and kinetics of GCE/MWCNT-NF/CAT/PEI for hydrogen peroxide (H₂O₂) showed the apparent Michaelis-Menten constant of 3mM, linear response in the range of 10μM to 5mM, response time of ~2s for steady state current, and detection limit of ~1μM. A high operational and storage stability was also demonstrated for the bioelectrode. Hence, the direct electrochemistry of the large catalase and its potential biosensor application have been established through this investigation.