Glucose　oxidase　was　encapsulated　in　carbon-nanotube/Nafion　film　modified　glass　carbon　electrode　and　was　used　as　electrochermiluminescence　(ECL)　biosensor　for　glucose.　The　glucose　oxidase　can　be　fixed　firmly　in　the　Nation　film　and　carbon　nanotubes　offer　excellent　electrocatalytic　activity　toward　luminol　and　hydrogen　peroxide　liberated　in　enzymatic　reaction　between　glucose　oxidase　and　glucose,　which　would　enable　sensitive　determination　of　glucose.　Under　the　optimum　condition,　the　linear　response　range　of　glucose　was　found　to　be　5.0　x　10(-6)　to　8.0　X　10(-4)　mol/L,　and　the　detection　limit　(defined　as　the　concentration　that　could　be　detected　at　the　signal-to-noise　ratio　of　3)　was　2.0　x　10(-6)　mol/L.　The　present　carbon-nanotube/Nafion　biocomposite　glucose　oxidase　ECL　biosensor　showed　excellent　properties　for　sensitive　determination　for　glucose　with　good　reproducibility　and　stability,　and　it　has　been　used　to　determine　the　glucose　concentrations　in　real　serum　samples　with　the　satisfactory　results.　(c)　2007　Elsevier　Ltd.　All　rights　reserved.