Stability and Sensitivity Enhanced Electrochemical In Vivo Superoxide Microbiosensor Based on Covalently Co-immobilized Lipid and Cytochrome c

Enhanced stability and sensitivity of a superoxide anion radical (O-2(center dot-)) microbiosensor were achieved through the sequential immobilization of lipid and cytochrome c (Cyt c) covalently bonded onto a conducting polymer layer that showed a clear quasi-reversible direct electron transfer (DET) process. The formal potential and the apparent standard rate constant were determined to be -0.24 V and 0.62 +/- 0.05 s(-1), respectively. The detection of O-2(center dot-) was attained through the catalytic activity of the haem group of Cyt c stabilized by coimmobilized lipid molecules (1,2-dipalmitoylsn-glycero-3-phosphoethanolamine-n-dodecanylamine (DGPD)). The linear dynamic range and the detection limit of the O-2(center dot-) analysis were determined to be 0.2-6.0 nM and 30.0 +/- 0.9 pM, respectively. The in vivo microbiosensor implanted into rat brain successfully determined the extracellular level of O-2(center dot-) produced by acute and repeated injections of cocaine. The present O-2(center dot-) microbiosensor could be an effective tool for monitoring the change in extracellular O-2(center dot-) levels in response to stimulant drug exposure.