The effector mechanism of siRNA spherical nucleic acids

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 117; no. 3; pp. 1312 - 1320
• Main Authors: Yamankurt, Gokay, Stawicki, Robert J., Posadas, Diana M., Nguyen, Joseph Q., Carthew, Richard W., Mirkin, Chad A.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 21.01.2020
• Subjects: Animals; Biological Sciences; Cell Line, Tumor; Cytotoxicity; Drosophila melanogaster; Gene silencing; Humans; Nanoparticles; Nanoparticles - chemistry; Nanoparticles - metabolism; Nanoparticles - toxicity; Nanostructure; Nucleic acids; Oligonucleotides; Organic chemistry; Physical Sciences; Ribonuclease III - metabolism; Ribonucleic acid; RNA; RNA Interference; RNA, Small Interfering - chemistry; RNA, Small Interfering - metabolism; RNA-mediated interference; siRNA; Strands; Toxicity; Transfection; spherical nucleic acids; gene regulation; siRNA processing
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1915907117

Spherical nucleic acids (SNAs) are nanostructures formed by chemically conjugating short linear strands of oligonucleotides to a nanoparticle template. When made with modified small interfering RNA (siRNA) duplexes, SNAs act as single-entity transfection and gene silencing agents and have been used as lead therapeutic constructs in several disease models. However, the manner in which modified siRNA duplex strands that comprise the SNA lead to gene silencing is not understood. Herein, a systematic analysis of siRNA biochemistry involving SNAs shows that Dicer cleaves the modified siRNA duplex from the surface of the nanoparticle, and the liberated siRNA subsequently functions in a way that is dependent on the canonical RNA interference mechanism. By leveraging this understanding, a class of SNAs was chemically designed which increases the siRNA content by an order of magnitude through covalent attachment of each strand of the duplex. As a consequence of increased nucleic acid content, this nanostructure architecture exhibits less cell cytotoxicity than conventional SNAs without a decrease in siRNA activity.