Multi-layered enzyme coating on highly conductive magnetic biochar nanoparticles for bisphenol A sensing in water

This work introduced stable immobilization of tyrosinase (TYR) enzymes onto the highly conductive magnetic biochar nanoparticles with carboxyl functionality to construct sensitive and reusable electrochemical biosensor for bisphenol A (BPA) detection. The newly synthesized biochar nanoparticles (BCNPs) from biomass had outstanding electrochemical activity, after functionalization with carboxylic functional groups and magnetic nanoparticles (Mag-BCNPs-COOH), it was used for multi-layered TYR immobilization with covalent attachment, precipitation and cross-linking method (ML-TYR/Mag-BCNPs-COOH). The BPA sensing system was simply constructed by directly attaching the biocatalyst of ML-TYR/Mag-BCNPs-COOH onto a glassy carbon electrode with magnet force. Owning to great properties of the ML-TYR/Mag-BCNPs-COOH, such as high stability, biocatalytic activity and conductivity, the BPA sensing signal was significantly enhanced. And the lowest detection limit of 2.78 nM with linear ranges from 0.01 to 1.01 μM was achieved. The modified electrode could be reused at least eight cycles without reducing the sensing signal, and could be used for the real environmental water detection.