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.