A　new　impedimetric　sensing　strategy　based　on　enzyme-triggered　formation　of　enzyme-tyramine　concatamers　on　the　nanogold-functionalized　poly(amidoamine)　(PAMAM)　dendrimer　was　designed　for　sensitive　detection　of　mercury(II)　(Hg2+)　ion,　coupling　with　enzymatic　biocatalytic　precipitation　towards　4-choloro-1-naphthol　(4-CN)　on　thymine　(T)-rich　single-stranded　DNA(r)-rmodified　electrode.　Initially,　nanogold-decorated　PAMAM　dendrimer　(AuNP-PAMAM)　was　synthesized　by　the　in-situ　reduction　method,　and　then　functionalized　with　horseradish　peroxidase　(HRP)　and　another　T-rich　oligomer　(DNA(2)).　Upon　target　Hg2+　introduction,　probe　DNA2　on　the　AuNP-PAMAM　bound　to　the　DNA(1)　on　the　electrode　owing　to　the　T-Hg2+-T　coordination　chemistry　between　the　two　DNA　strands.　Accompanying　the　AuNPPAMAM,　the　carried　HRP　could　trigger　the　formation　of　HRP-tyramine　concatamer　via　the　classical　tyramine　signal　amplification　strategy　in　the　presence　of　HRP-tyramine　conjugates　and　hydrogen　peroxide.　The　concatenated　HRP　molecules　in　the　concatamer　catalyzed　the　4-CN　oxidation　to　produce　an　insoluble　precipitation　on　the　electrode,　thereby　resulting　in　the　local　alteration　in　the　conductivity.　Under　optimal　conditions,　two　signal-generation　tags　including　HRP-AuNP-DNA2　and　HRP-AuNP-PAMAM-DNA(2)　with　or　without　tyramine　signal　amplification　strategy　(i.e.,　four　schemes)　were　used　for　impedimetric　detection　of　target　Hg2+　on　the　basis　of　the　same　assay　format.　A　low　detection　limit　(LOD)　of　0.4　pM　and　a　wide　dynamic　working　range　of　0.001-100　nM　Hg2+　by　using　HRP-AuNP-PAMAM-DNA(2)　with　tyramine　signal　amplification　strategy　were　obtained　in　comparison　with　those　of　other　strategies.　The　assay　had　a　good　repeatability　and　showed　an　intermediate　precision　of　down　to　9.6%.　In　addition,　the　methodology　also　exhibited　high　specificity　and　selectivity　towards　target　Hg2+　against　other　metal　ions,　and　was　applicable　for　monitoring　Hg2+　in　the　spiked　drinking　water　samples.　(C)　2015　Elsevier　B.V.　All　rights　reserved.