Improved enzyme immobilization for enhanced bioelectrocatalytic activity of choline sensor and acetylcholine sensor

In this work, we report the development of a highly sensitive and stable choline/acetylcholine sensor based on the synergetic effect of multi-walled carbon nanotubes and ZnO nanoparticles. This unique multi-layer structure provided a favorable microenvironment to maintain the bioactivity of choline oxidase and acetylcholinesterase, which led to a rapid amperometric response to choline and acetylcholine. This nanomaterials-based choline/acetylcholine sensor was highly sensitive and showed good stability over a relatively long-term storage (90 days). The sensor prepared by loading 1.0-unit choline oxidase and acetylcholinesterase showed a linear response range of 1.0 mu M to 0.8 mM and 1.0 mu M to 1.0 mM, a sensitivity of 178 mu A mM(-1) cm(-2) and 180 mu A mM(-1) cm(-2), and a detection limit of 0.3 mu M, respectively. The sensor prepared was used to detect choline in human blood plasma samples, and the obtained results were consistent with those of the HPLC-MS/MS assay. (C) 2013 Elsevier B.V. All rights reserved.