An　ultrasensitive　and　selective　miRNA　biosensor　based　on　the　luminol-H2O2　electrochemiluminescence　(ECL)　system　using　hemin　as　a　catalyzer　for　in　situ　ECL　signal　enhancement　was　reported.　DNA　probe　was　tethered　onto　the　electrodeposited　Au　nanoparticles　on　a　glassy　carbon　electrode,　and　the　remaining　active　sites　were　then　blocked　with　glucose　oxidase　(GOD).　Subsequently,　followed　by　miRNA　hybridizing　with　the　DNA　probe,　hemin　molecules　acted　as　the　essential　enhancer　of　ECL　were　intercalated　into　the　DNA/miRNA　duplex　structure.　The　fully　constructed　biosensor　was　placed　in　a　phosphate　buffered　solution　containing　luminol　and　glucose,　where　glucose　was　enzymatically　decomposed　by　GOD　to　H2O2.　Formation　of　reactive　oxygen　species　(O-2(-center　dot))　from　H2O2,　which　was　a　key　step　for　luminol　ECL　production,　was　efficiently　catalyzed　by　the　intercalated　hemin.　Thus,　enhanced　ECL　signal　was　obtained.　Under　the　optimal　conditions,　this　miRNA　biosensor　could　sensitively　and　selectively　detect　target　miRNA　over　approximately　seven　orders　of　magnitude　between　0.050　and　1.0　x　10(5)　pM,　with　a　limit　of　detection　of　50　fM.　miRNAs　extracted　from　the　A459　cell　line　were　quantified　with　the　biosensor.　The　ECL　enhancement　strategy　presented　in　this　paper　could　open　a　new　route　for　the　development　of　extremely　sensitive　ECL　based　biosensors.　(C)　2017　Elsevier　B.V.　All　rights　reserved.