On-line regeneration of electrochemical biosensor for in vivo repetitive measurements of striatum Cu2+ under global cerebral ischemia/reperfusion events

The detection of Cu2+ ion, one of the metal ions substantial in cerebral physiology, is critical in studying brain activities and understanding brain functions. However, repetitive measurements of Cu2+ in the progress of physiological and pathological events is still challenging, because lack of the platform for repetitive on-line detection-regeneration cycle. Herein we report the design of a regenerated electrochemical biosensor combined with the in vivo microdialysis system. In this biosensor, hyperbranched polyethyleneimine (hPEI) acts as a regenerated recognition unit for Cu2+. Just by a simple rinse of ethylenediaminetetraacetic acid (EDTA) disodium salt, the Cu2+ and Cu+ ions on the biosensor interface were chelated with EDTA disodium salt, thus achieving the regeneration of the biosensor. In addition, 6-(ferrocenyl)hexanethiol (FcHT) serves as the inner reference moiety to elevate the sensing accuracy over regeneration cycles. As a result, this ratiometric electrochemical biosensor not only revealed high sensitivity and selectivity, but also exhibited excellent stability during multiple regeneration processing. This biosensor was capable of determining Cu2+ with a linear range between 0.05 and 12 μM and low detection limit (LOD) of 13 nM. Then, the platform has been successfully applied in repetitive Cu2+ analysis in rat brain under global cerebral ischemia/reperfusion events. The combination of results from 7 rats indicates global cerebral ischemia caused an obvious increase of the Cu2+ level, while reperfusion brought this level back to normal.