A single-use cartridge for performing an immunoassay, comprising: a sample entry port for receiving a biological sample suspected of containing a target analyte, a conduit containing an electrode, a region containing a wash fluid, and a waste chamber, wherein an immunoassay is formed on said electrode, the immunoassay comprising immobilized first antibody bound to said target analyte, second antibody to said target analyte, wherein the second antibody is attached to a first single stranded oligonucleotide; and one or more signal elements each attached to a second single stranded oligonucleotide having complimentary base pairs to the first single stranded oligonucleotide; wherein said first single stranded oligonucleotide has at least two repeated sequences which bind to at least two of the second sequences of the second single stranded oligonucleotide, preferably the first single stranded oligonucleotide has at least three repeated sequences which bind to at least three of the second sequences of the second single stranded oligonucleotide, more preferably the first single stranded nucleotide has at least five repeated sequences which bind to at least five of the second sequences of the second single stranded oligonucleotide; wherein the wash fluid is capable of washing said biological sample from said electrode in said conduit into said waste chamber; wherein the second antibody is disposed in a solubilizing agent disposed within the conduit; and wherein a 3'-end or 5'-end of the first single stranded oligonucleotide and the second single stranded oligonucleotide is protected from endogenous exonuclease activity in the sample by incorporating a protective chemical group. a sample entry port for receiving a biological sample suspected of containing a target analyte, a conduit containing an electrode, a region containing a wash fluid, and a waste chamber, wherein an immunoassay is formed on said electrode, the immunoassay comprising immobilized first antibody bound to said target analyte, second antibody to said target analyte, wherein the second antibody is attached to a first single stranded oligonucleotide; and one or more signal elements each attached to a second single stranded oligonucleotide having complimentary base pairs to the first single stranded oligonucleotide; immobilized first antibody bound to said target analyte, second antibody to said target analyte, wherein the second antibody is attached to a first single stranded oligonucleotide; and one or more signal elements each attached to a second single stranded oligonucleotide having complimentary base pairs to the first single stranded oligonucleotide; wherein said first single stranded oligonucleotide has at least two repeated sequences which bind to at least two of the second sequences of the second single stranded oligonucleotide, preferably the first single stranded oligonucleotide has at least three repeated sequences which bind to at least three of the second sequences of the second single stranded oligonucleotide, more preferably the first single stranded nucleotide has at least five repeated sequences which bind to at least five of the second sequences of the second single stranded oligonucleotide; wherein the wash fluid is capable of washing said biological sample from said electrode in said conduit into said waste chamber; wherein the second antibody is disposed in a solubilizing agent disposed within the conduit; and wherein a 3'-end or 5'-end of the first single stranded oligonucleotide and the second single stranded oligonucleotide is protected from endogenous exonuclease activity in the sample by incorporating a protective chemical group.