In　this　study,　an　electrochemical　DNA　biosensor　was　developed　for　detection　of　the　breakpoint　cluster　region　gene　and　the　cellular　abl　(BCR/ABL)　fusion　gene　in　chronic　myelogenous　leukemia　by　using　18-mer　locked,　nucleic　acid-modified,　single-stranded　DNA　as　the　capture　probe.　The　capture　probe　was　covalently　attached　on　the　sulfonic-terminated　aminobenzenesulfonic　acid　monolayer-modified　glassy　carbon　electrode　through　the　free　amines　of　DNA　bases　based　on　the　acyl　chloride　cross-linking　reaction.　The　covalently　immobilized　capture　probe　could　selectively　hybridize　with　its　target　DNA　to　form　double-stranded　DNA　(dsDNA)　on　the　LNA/4-ABSA/GCE　surface.　Differential　pulse　voltammetry　was　used　to　monitor　the　hybridization　reaction　on　the　capture　probe　electrode.　The　decrease　of　the　peak　current　of　methylene　blue,　an　electroactive　indicator,　was　observed　upon　hybridization　of　the　probe　with　the　target　DNA.　The　results　indicated　that,　in　pH　7.0　Tris-HCl　buffer　solution,　the　peak　current　was　linear　with　the　concentration　of　complementary　strand　in　the　range　of　1.0　×　10-12-1.1　×　10-11　M　with　a　detection　limit　of　9.4　×　10-13　M.　This　new　method　demonstrates　its　excellent　specificity　for　single-base　mismatch　and　complementary　dsDNA　after　hybridization,　and　this　probe　has　been　used　for　assay　of　PCR　real　sample　with　satisfactory　results.　©　2008　American　Chemical　Society.