Carbon-nanotube-supported POXA1b laccase and its hydrophobin chimera for oxygen reduction and picomolar phenol biosensing

The immobilization of POXA1b laccase and its hydrophobin-fused chimera was performed at pristine Multiwalled Carbon Nanotube (MWCNT) and MWCNT-modified electrodes by electrografting of a 2-diazoniumanthraquinone salt. The influence of the hydrophobin domain and the MWCNT functionalization with anthraquinone groups towards immobilization of laccase was compared by direct electrochemistry under O2 and electrochemical biosensing of phenols. The hydrophobin domain affords the stable dispersion of MWCNT in water/ethanol, while being detrimental to the direct electron transfer between POXA1b and the electrode. On the contrary, the stronger hydrophobic interactions between anthraquinone and laccase affords direct electrochemistry of POXA1b and enabled the design of a highly sensitive phenol biosensor, reaching a limit-of-detection (LOD) of 2 pM and sensitivity of 23,600 mA L mmol−1 cm−2 for catechol, and a LOD of 15 nM and sensitivity of 0.053 mA L mmol−1 cm−2 for dopamine. -POXA1b and its hydrophobin-fused chimera were immobilized on modified MWCNTs-The surfactant ability of POXA1b-Vmh2 was demonstrated towards MWCNT water/ethanol dispersion-Direct oxygen reduction is observed for POXA1b immobilized on anthraquinone-modified MWCNT electrode-Catechol biosensing exhibits a LOD of 2 pM and sensitivity of 23,600 mA L mmol−1 cm−2-Dopamine biosensing exhibits a LOD of 15 nM and sensitivity of 0.053 mA L mmol−1 cm−2