Multitasking by Multivalent Circular DNA Aptamers

Abstract

Nucleic acid aptamers are finding increasing applications in biology, especially as therapeutic candidates and diagnostic components. An important characteristic in meeting the needs of these applications is improved stability in physiological fluids, which is most often accomplished with chemical modification or unnatural nucleotides. In an alternative approach we have specified the design of a multivalent circular DNA aptamer topology that encompasses a number of properties relevant to nucleic acid therapeutic candidates, especially the ability to multitask by combining different activities together within a modular structure. Improved stability in blood products, greater conformational stability, antidoting by complementary circular antiaptamers, heterovalency, transcription factor decoy activity and minimal unintended effects upon the cellular innate immune response are desirable properties that are described here. Multitasking by circular DNA aptamers could similarly find applications in diagnostics and biomaterials, where the combination of interchangeable modules might generate new functions, such as anticoagulation coupled with reversible cell capture as, described here. These results provide a platform for further exploration of multivalent circular aptamer properties, especially in novel combinations of nucleic acid therapeutic modes.

Bi-specific Aptamers Mediating Tumor Cell Lysis

“…versus exposed termini (5). In addition to high affinity simultaneous binding, bsA serum stabilities provided clear evidence of the suitability for functional evaluation.…”

“…Reversely, bi-and multivalent aptamers can activate co-stimulatory receptors, e.g. to enhance T cell reactivity (5,6). Finally, aptamers can be applied in ligand-based targeted therapies to specifically deliver cytotoxic payloads (7,8) or siRNA (9) to tumor cells.…”

“…Development of monovalent therapeutic antibodies is elaborate and time-intensive (MetMAb (12)). Although antibodies exceed aptamers with proof as therapeutic molecules, high stability, and good pharmacokinetics, the potential advantages of aptamers are a rapid optimization, cost-effective and uniform synthesis, and a high probability of an absence of immunogenicity (5,13). Approval of Macugen (pegaptanib sodium (14)) as the first therapeutic aptamer in 2007 as well as promising approaches in preclinical development and clinical trials (15,16) only a few years after inception of the technology indicate aptamers as a promising new class of targeted therapeutics.…”

Aptamers: Problems, Solutions and Prospects

“…Several different aptamers can also be ligated to a closed structure with multiple specificities [29, 30]. The generation of such ring structures is an optimal approach for the regular injection of high amounts of aptamers, since the degradation products of some modified oligonucleotides have the potential of being toxic [31].…”

Devices and approaches for generating specific high-affinity nucleic acid aptamers

“…Finally, it is possible to link together multiple aptamers to generate multivalent aptamers that can bind multiple identical targets or bind multiple sites on a single target to enhance target recognition, or even to create aptamers that recognize novel combinations of target molecules. [7][8][9][10][11][12] The potential impact for aptamers and their resultant technologies is just beginning to be understood. Almost 10 years ago, the first aptamer was approved by the Food and Drug Administration to treat neovascular age-related macular degeneration.…”