RNA interference has been widely used for gene therapy of various infectious diseases and malignant tumors. However, its poor stability in serum has limited further clinic application. Here, we found that stability of siRNA in serum enhanced obviously when 3′-terminus of sense strand （siRNA-pS） was conjugated with peptide, while same conjugation at 3′-terminus of antisense strand brought no such effects. And it was also found that only the peptide residue in siRNA-pS could be cut off by RNase A. All these results indicated that nucleases in serum prefer to invade siRNA duplex through the 3′-end of sense strand.
Synthetic oligonucleotides including antisense oligonucleotides and siRNA have shown promising therapeutic potential.However,to realize the therapeutic potential of synthetic oligonucleotides,many obstacles have to be overcome,such as their poor biological stability,non-specific activity and inadequate cell membrane permeability.In this paper,the achievements by Lihe Zhang＇s group in the study of isonucleotide modified oligonucleotides and oligonucleotides conjugated with cell penetrating peptides are summarized.
Stability, specificity, and pharmacokinetic properties are some of the challenges facing RNAi therapeutics. In this review, the progresses in chemically modified siRNAs and siRNA conjugates are summarized. The proper modification of siRNA with nucleoside analogues, construction of siRNA conjugates, and reliable prediction of the property based on those strategies for a given siRNA sequence would certainly be an essential part of the solution to these challenges.
