In vivo characterisation of a catalase-based biosensor for real-time electrochemical monitoring of brain hydrogen peroxide in freely-moving animalsElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ay03066a

A catalase-based microelectrochemical biosensor developed for real-time neurochemical monitoring of hydrogen peroxide (H 2 O 2 ) was characterised in freely-moving rats. The in situ sensitivity of the sensor was assessed by the direct delivery of H 2 O 2 to the local environment of the implanted sensor and by the chemical manipulation of the endogenous concentration of H 2 O 2 . Inhibitors of H 2 O 2 enzymatic degradation were utilised including sodium azide (SA) and mercaptosuccinate (MCS). SA and MCS primarily inhibit catalase and glutathione peroxidase (GPx) respectively and the application of each resulted in a significant increase in the H 2 O 2 signal. The selectivity of the sensor was verified by the absence of a change in the signal in response to the peripheral administration of ascorbic acid (AA) compared to controls. Evidence of a disparity between brain H 2 O 2 signalling in the freely-moving animal with respect to the anaesthetised subject was also observed. The enzymatic component of the paired H 2 O 2 sensor was found to be stable over a continuous monitoring period of 12 days, thereby demonstrating the suitability of this sensor for the long-term chronic detection of brain H 2 O 2 . A catalase-based microelectrochemical biosensor developed for real-time neurochemical monitoring of hydrogen peroxide (H 2 O 2 ) was characterised in freely-moving rats.