Recent years have seen the development of a number of reagentless, electrochemical sensors based on the target-induced folding or other target-induced conformational changes in electrode-bound oligonucleotides, with examples reported to date including sensors for the detection of specific nucleic acids, proteins, small molecules and inorganic ions. These of sensors, termed Electrochemical DNA-based (E-DNA) sensors, are comprised of an electrode modified with surface immobilized, redox-reporter-tagged DNA probes. This technique has emerged as a promising new biosensor platform due to its sensitive and selective measurement of specific molecular targets without the need for additional reagents, wash steps or complex and costly equipment. My thesis work has focused on expanding and improving this increasingly important sensing platform. We have expanded the number of signaling redox reporter for multiplexing and ratiometric auto-calibration sensing. As well as we developed a simple strategy to rationally edit the useful dynamic range of our electrochemical DNA sensors. To make our platform more generic for sensing, we designed a novel protein-based electrochemical sensing architecture achieves good specificity and sensitivity, providing a new approach for the quantitative, single-step measurement of protein-macromolecule interactions. At the end, we have used surface forces apparatus (SFA) to study the behavior of surface grafted single-stranded and double-stranded DNAs.