"Oligonucleotides, in the form of DNA and RNA are primarily known as the information and messenger molecules of the cell. Roles beyond this informational molecule have seen oligonucleotides used as structural materials, therapeutics, and molecular recognition components. Combining many of these different roles, the field of DNA nanotechnology has emerged, to generate an unprecedented number of different devices, for applications in sensing, diagnostics, gene silencing and drug delivery. Especially in the case of gene silencing and drug delivery, the biocompatibility, and recognition abilities of DNA place these nanostructures as advantageous carriers for the transport and selective release of these agents. However, by its nature, DNA is chemically inert and to gain more function, chemical modifications are generally needed. This thesis presents new oligonucleotide conjugates used in combination with DNA nanotechnology for the selective delivery/release of both small molecule drugs and antisense oligonucleotides. At first, the evolution of a DNA device that was engineered to selectively amplify the release of small molecule therapeutics, in response to a molecular recognition event is described. A detailed investigation into the design, conjugation chemistry, and kinetics of release are presented. Furthermore, integrating structural DNA nanotechnology and the drug release platform together allows for the generation of well-defined nanostructures which can act as standalone devices without multiple components. Secondly, a new antisense oligonucleotide conjugated with hydrophobic disulfide modifications is generated for their ability to self-assemble into spherical nucleic acids and produce stimuli responsive gene silencing under reducing conditions. The stability of these structures in cellular media and uptake into cells of these structures is thoroughly investigated. Finally, different strategies to improve the drug release device from Chapter 2 for transitioning it into real biological drug delivery applications is developed. Factors such as off-target degradation/activation, delivery to the site of action, rate of metabolism and overall drug specificity are addressed"--