Figure 7. Examination of the stability of phosphorothiolated DNA.

(A) Chemical structure of ID₁ on the top layer hydrogel. The backbone of ID₁ has the phosphorothioate bond resistant to nuclease degradation. The 3′ ends was modified with the inverted T. (B) Gel electrophoresis image demonstrating the resistance of ID₁ against nuclease degradation during the 7-day degradation test. After ID₁ was degraded in the cell culture medium for different days, CD₁ was added into ID₁ solutions before gel electrophoresis. (C) Gel image of the ID₁-CD₁ duplex before and after the incubation in the cell culture medium in a two-round test. The duplex was incubated in the cell culture medium for 24 h. This procedure was repeated after the duplex solution was added with fresh CD₁.