A　highly　performing　ECL　glucose　biosensor　was　developed　by　immobilizing　glucose　oxidase　(GOD)　onto　a　membrane　modified　glassy　carbon　electrode,　which　was　prepared　by　using　poly(diallyl-dimethylammonium　chloride)　(PDDA)　doped　with　chitosan.　In　order　to　obtain　the　optimal　performance　of　the　ECL　biosensor,　the　composition　of　modified　membranes　and　a　series　of　measurement　conditions　were　investigated.　Under　the　optimal　conditions,　this　ECL　biosensor　was　able　to　detect　glucose　in　the　range　of　0.5-4.0　x　10(4)　nM　with　a　detection　limit　of　0.1　nM　(defined　as　the　concentration　that　could　be　detected　at　the　signal-to-noise　ratio　of　3).　The　relative　standard　deviation　was　0.99%　for　5　x　10(-8)　mol/L　glucose　in　repetitive　measurements　in　the　primary　12　potential　cycles.　This　ECL　biosensor　offered　the　effectively　improved　stability　of　the　electron　transfer　mediator　and　exhibited　excellent　properties　for　the　ultrasensitive　and　selective　determination　of　glucose　with　good　reproducibility　and　stability.　The　present　biosensor　has　also　been　used　to　determine　the　glucose　concentrations　in　real　serum　samples.　The　recovery　value　for　the　assay　of　glucose　ranged　from　96.2　to　107%　in　the　serum　samples.　The　present　biosensor　displayed　both　specificity　for　glucose　and　retention　of　signal　response　even　in　a　complex　environment.　Therefore,　it　provided　an　approach　to　the　sensitive　determination　of　glucose.　(C)　2009　Elsevier　Ltd.　All　rights　reserved.