Fabrication of tyrosinase biosensor based on multiwalled carbon nanotubes-chitosan composite and its application to rapid determination of coliforms

A tyrosinase (Tyr) biosensor was fabricated by immobilizing Tyr on the surface of multiwalled carbon nanotubes (MWNTs)-chitosan (Chit) composite modified glassy carbon electrode (GCE). The MWNTs-Chit composite film provided a biocompatible platform for the Tyr to retain the bioactivity and the MWNTs possessed excellent inherent conductivity to enhance the electron transfer rate. The Tyr/MWNTs-Chit/GCE biosensor showed high sensitivity (412 mA/M), broad linear response (1.0 x 10(-8)-2.8 x 1.0(-5) M), low detection limit (5.0 nM) and good stability (remained 93% after 10 days) for determination of phenol. The biosensor was further applied to rapid detection of the coliforms, represented by Escherichia coli (E. coli) in this work. The current responses were proportional to the quantity of coliforms in the range of 10(4)-10(6) cfu/mL. After 5.0 h of incubation, E. coli could be detected as low as 10 cfu/mL.