Triazole- and Tetrazole-Bridged Nucleic Acids: Synthesis, Duplex Stability, Nuclease Resistance, and in Vitro and in Vivo Antisense Potency.

Antisense oligonucleotides are attractive therapeutic agents for several types of disease. One of the most promising modifications of antisense oligonucleotides is the introduction of bridged nucleic acids. As we report here, we designed novel bridged nucleic acids, triazole-bridged nucleic acid (TrNA), and tetrazole-bridged nucleic acid (TeNA), whose sugar conformations are restricted to N-type by heteroaromatic ring-bridged structures.

Effect of an N-substituent in sulfonamide-bridged nucleic acid (SuNA) on hybridization ability and duplex structure.

A sulfonamide-bridged nucleic acid without an N-substituent (SuNA[NH]) was successfully synthesized. A comparison of the SuNA[NMe]- and SuNA[NH]-modified oligonucleotides revealed that the duplex-forming abilities of the SuNA[NMe]-modified oligonucleotides with complementary DNA and RNA were higher than those of the SuNA[NH]-modified oligonucleotides. The crystal structures of DNA duplexes containing a SuNA[NR] revealed that the helical structures of the two duplexes and hydration patterns around the bridge moiety were different.

Ca2+ enrichment in culture medium potentiates effect of oligonucleotides.

Antisense and RNAi-related oligonucleotides have gained attention as laboratory tools and therapeutic agents based on their ability to manipulate biological events in vitro and in vivo. We show that Ca(2+) enrichment of medium (CEM) potentiates the in vitro activity of multiple types of oligonucleotides, independent of their net charge and modifications, in various cells. In addition, CEM reflects in vivo silencing activity more consistently than conventional transfection methods.