In this manuscript, an electrochemical DNA hybridization biosensor which exploits long range charge transfer through double stranded DNA (ds-DNA) to copper-phthalocyanine tetrasulfonic acid - tetra sodium salt (CuPcS4) is described. Four negative charges of CuPcS4 make it a good choice to overcome two main problems of the biosensors: direct electron transfer with the electrode surface instead of charge transfer through DNA and positioning of the redox reporter before the mismatch position. The DNA recognition layer consisted of a self assembled monolayer of amino modified single stranded DNA (ss-DNA) on the surface of glassy carbon electrode (GCE). A significant increase of the peak current for CuPcS4 upon the hybridization process is observed. This biosensor can differentiate complementary target from non-complementary and also different types of single-base mismatch targets even thermodynamically stable G-A and G-T targets through diminution of voltammetric signal of CuPcS4. In addition, the position of the mismatch does not affect on the capability of the biosensor. (C) 2010 Elsevier B.V. All rights reserved.