A three-enzyme microelectrode sensor for detecting purine release from central nervous system

As the purines, in particular adenosine, are important signaling agents in the nervous system we have devised a new biosensor for directly measuring their production in real time during physiological activity. Our amperometric adenosine biosensor is made by entrapping 3 enzymes (xanthine oxidase, purine nucleoside phosphorylase and adenosine deaminase) in a composite lactobionamide and amphiphillic polypyrrole matrix around a Pt microelectrode. The resulting sensors are small (25-100 microm diameter), fast responding (10-90% rise time, 2+/-0.23 s), sensitive (100-222 mA M(-1) cm(-2)) and stable (100% activity after 5 days). The sensor was used in vivo to demonstrate the spatial localization of release of adenosine from Xenopus embryo spinal cord during fictive swimming.