At present, there is no chemical system for efficient synthesis of stereospecific phosphorothioate siRNAs (PS-siRNAs), this research designed the modified siRNA to target PLK1 for cancer therapy, enzymatically synthesized Rp phosphorothioate siRNAs (Rp-PS-siRNAs) with ATPaS, CTPaS, UTPaS by T7 RNA polymerase, and studied the differences between the nat-siRNAs and PS-siRNAs in serum stability and gene silencing activities. The data showed that the phosphorothioate modification introduced by the enzymatic catalysis could significantly improve the serum stability of siRNA while conserving the siRNA interference efficiency. Therefore, the Rp-PS-siRNA via enzymatic synthesis is of potential properties for developing siRNAs as biomedical research tools with a longer half-life in gene silencing.
