Synthesis, serum stability and cell uptake of cyclic and hairpin decoy Oligonucleotides for TCF/LEF and GLI transcription factors

A series of hairpin oligonucleotides bearing a 5?-alkyne and 3?-azide were cyclised using the CuAAC reaction to form cyclic decoys for targeting the DNA binding site of the TCF/LEF and GLI transcription factors. Incubation of a fluorescent hairpin oligomer and its cyclic analogue in fetal calf serum showed that the cyclic construct has significantly greater stability to enzymatic degradation. Cell uptake studies using HEK-293 cells with the fluorescent cyclic decoy in the presence of lipofectamine 2000 transfection agent indicated that this analogue is taken up by the cells and localizes to the cell nucleus. Localized fluorescence was observed in the nuclei of HEK-293 cells after only 1.5 h incubation which increased over a period of 4 h and persisted for 24 h