A tyrosinase biosensor based on ZnO nanorod clusters/nanocrystalline diamond electrodes for biosensing of phenolic compounds.

An amperometric biosensor was constructed by using ZnO nanorod clusters as platforms for immobilizing tyrosinase on the nanocrystalline diamond (NCD) electrodes. The results showed that ZnO nanorod clusters provided an advantageous microenvironment due to their favorable isoelectric point (IEP) for tyrosinase loading; immobilized tyrosinase generally retained its activity. The tyrosinase/ZnO/NCD electrode showed a linear response range of 1-210 and sensitivity of 179.9 microA mmol(-1) cm(-2) for p-cresol. The corresponding values were 1-190 and 90.2 for phenol, and 1-250 and 121.3 for 4-chlorophenol. The low detection limits were estimated to be 0.2 microM for p-cresol, 0.5 microM for phenol, and 0.4 microM for 4-chlorophenol (S/N = 3). The prepared enzyme electrode could keep 85% of its original activity after intermittent use for 4 weeks when stored in a dry state at 277 K. Therefore, the ZnO nanorod cluster thin films have potential applications as platforms to immobilize other enzymes and bioactive molecules in biosensors.