A　simple　and　sensitive　DNAzyme-based　colorimetric　sensor　for　detecting　Hg2+　based　on　T-Hg2+-T　base　pair　and　magnetic　beads　(MBs)　is　proposed.　In　the　presence　of　Hg2+,　capture　probes　(CPs)　immobilized　on　MBs　are　hybridized　with　the　signal　probes　(SPs)　consisting　of　G-quadruplex　sequences　with　the　help　of　T-Hg2+-T　base　pairs.　The　SPs　are　separated　by　MBs　and　used　to　bind　hemin　for　the　formation　of　catalytically　active　hemin/G-quadruplex　DNAzymes,　which　catalyzes　the　H2O2-mediated　oxidation　of　ABTS　to　produce　a　blue-green-colored　product.　A　linear　relationship　between　the　absorbance　and　Hg2+　concentration　is　observed　over　a　range　of　10-200　nM　with　a　limit　of　detection　5　nM.　Taking　advantage　of　MBs　separation/collection　process,　the　sensing　system　can　be　regenerated　by　using　EDTA　as　the　chelator.　(C)　2013　Elsevier　B.V.　All　rights　reserved.