Chemical Modifications of siRNA for Improved Stability and Reduced Immunogenicity
Synthetic siRNA molecules are vulnerable to degradation by cellular nucleases and can trigger unintended immune responses, which pose challenges for efficient and safe gene silencing. To overcome these issues, various chemical modifications have been developed to enhance siRNA stability, specificity, and biocompatibility.
Modifications commonly involve altering the sugar backbone, bases, or phosphate linkages of siRNA strands. Incorporating 2’-O-methyl or 2’-fluoro modifications on the ribose sugar increases resistance to ribonucleases, thereby extending siRNA half-life inside cells and biological fluids. Phosphorothioate linkages, where a non-bridging oxygen is replaced by sulfur in the phosphate backbone, also provide enhanced nuclease resistance and improve pharmacokinetic properties.
Another key consideration is minimizing immunogenicity. Unmodified siRNA can activate innate immune sensors such as Toll-like receptors (TLRs), leading to inflammatory responses and off-target effects. Chemical modifications at specific positions can reduce recognition by these receptors. For example, 2’-O-methylation on the passenger strand decreases activation of TLR7 and TLR8, mitigating cytokine release.
Additionally, chemical modifications influence strand selection and incorporation into the RNA-induced silencing complex (RISC), potentially enhancing knockdown efficacy. Proper design balances stability, immunogenicity, and potency to maximize therapeutic and experimental outcomes.
These advances in siRNA chemistry have made RNA interference a more reliable and safe approach for gene silencing in both in vitro research and in vivo therapeutic applications.
References: Altogen.com Altogenlabs.com