Abstract: In accordance with the present invention, there are provided systems for detecting hybridization of nucleic acids using electrochemical methods having improved sensitivity. Such systems include an electrode having a variably charged oligonucleotide probe and a redox probe. In some embodiments, the systems may further include a binding nexus having an immobilized reporter oligonucleotide probe, which hybridizes to a target nucleic acid sequence. The reporter oligonucleotide probe may be naturally charged, uncharged, or either partially negatively or positively charged. Further provided are methods for detecting the presence of a nucleic acid sequence of interest in a sample.