Determination of Total Monoamines in Rat Brain via Nanotubes Based Human Monoamine Oxidase B Biosensor

A specific and sensitive electrochemical biosensor with human monoamine oxidase B (hMAO B) as biological receptor and a MnO2 modified nanomaterial based transducer system has been developed and optimised. Best results for the biosensor were achieved when using enzyme immobilisation with a dialysis membrane (regenerated cellulose, molecular weight cut-off 14000) and a 20% (m/m) MnO2 modified multi-walled carbon nanotubes (MWCNTs, ratio of fluid to solid compounds of 1:0.7 (m/m)) paste electrode smoothed with a glassy carbon paste (GCP, ratio 1:3.6 (m/m)) containing the same mediator concentration. The biosensor was operated in a flow injection analysis (FIA) system with SOrensen phosphate buffer (33mM, pH7.5) and amperometric detection at a fixed potential of +400mVvs. Ag/AgCl. The developed sensor underwent validation using phenylethylamine (PEA) as standard substrate showing linearity between 5.0 and 400 mu M PEA and limits of detection and quantification of 1.5 and 5.0 mu M PEA, respectively. The sensor was successfully tested for the determination of total monoamines in rat brain calculated as PEA equivalents showing a result of 1.2 mu g/g brain tissue (n=3, relative standard deviation 4.4%).