Redox-active biomineralised zeolitic imidazolate frameworks enable peroxidase bioelectrocatalysis with shielding against substrate inhibition and thermal inactivation

Abstract

Oxidoreductase enzymes have remarkable advantages in terms of activity and selectivity but their fragility and buried active sites hinder their practical use for bioelectrochemical applications. Solutions are required to address the limited stability of enzyme-electrode interfaces while permitting efficient electron transfer, especially under harsh inhibiting and deactivating conditions. Inspired by natural biomineralisation, we developed a protected redox-active biomineralised peroxidase/zeolitic imidazolate framework electrode in which the fragile enzyme is electrically-accessible and shielded from substrate inhibition and thermal deactivation. In contrast to previous biomimetic metal organic frameworks developed for biocatalysis, the biomineralised frameworks reported here comprised enzyme together with a benzothiazoline redox mediator to enable electron shuttling across and/or from the crystalline matrix. Both redox entities proved necessary to overcome the insulating zeolitic framework barrier. This strategy provided benefits such as 3-fold enhanced bioelectrocatalytic currents and remarkable protection at high inhibitor (peroxide) concentrations of ca. 0.5–5 mmol L⁻¹ up to 50 °C. The protective framework offered improved 1-week storage stability and permitted biosensor linear range expansion from 0.1 to 0.5 mmol L⁻¹. Limitations were observed in terms of sensor sensitivity and high temperature deactivation. Redox-active biomineralised MOFs hold promise for extending bioelectrocatalytic outputs under harsh conditions for future biosensors, biofuel cells and bioreactors.