Biofuel cell-based self-powered biogenerators for online continuous monitoring of neurochemicals in rat brain.

This study demonstrates a new electrochemical method for continuous neurochemical sensing with a biofuel cell-based self-powered biogenerator as the detector for the analysis of microdialysate continuously sampled from rat brain, with glucose as an example analyte. To assemble a glucose/O(2) biofuel cell that can be used as a self-powered biogenerator for glucose sensing, glucose dehydrogenase (GDH) was used as the bioanodic catalyst for the oxidation of glucose with methylene green (MG) adsorbed onto single-walled carbon nanotubes (SWNTs) as the electrocatalyst for the oxidation of dihydronicotinamide adenine dinucleotide (NADH). Laccase crosslinked onto SWNTs was used as the biocathodic catalyst for the O(2) reduction. To enable the bioanode and biocathode to work efficiently in their individually favorable solutions and to eliminate the interference between the glucose bioanode and O(2) biocathode, the biofuel cell-based biogenerator was built in a co-laminar microfluidic chip so that the bioanodic and biocathodic streams could be independently optimized to provide conditions favorable for each of the bioelectrodes. By using a home-made portable voltmeter to output the voltage generated on an external resistor, the biogenerator was used for glucose sensing based on a galvanic cell mechanism. In vitro experiments demonstrate that, under the optimized conditions, the voltage generated on an external resistor shows a linear relationship with the logarithmic glucose concentration within a concentration range of 0.2 mM to 1.0 mM. Moreover, the biogenerator exhibits a high stability and a good selectivity for glucose sensing. The validity of the biofuel cell-based self-powered biogenerator for continuous neurochemical sensing was illustrated by online continuous monitoring of striatum glucose in rat brain through the combination of in vivo microdialysis. This study offers a new and technically simple platform for continuously monitoring physiologically important species in cerebral systems.