Investigation of the interaction between split aptamer and vascular endothelial growth factor 165 using single molecule force spectroscopy

Understanding the binding of split aptamer/its target could become a breakthrough in the application of split aptamer. Herein, vascular endothelial growth factor (VEGF), a major biomarker of human diseases, was used as a model, and its interaction with split aptamer was explored with single molecule force spectroscopy (SMFS). SMFS demonstrated that the interaction force of split aptamer/VEGF(165) was 169.44 +/- 6.59 pN at the loading rate of 35.2 nN/s, and the binding probability of split aptamer/VEGF(165) was dependent on the concentration of VEGF(165). On the basis of dynamic force spectroscopy results, one activation barrier in the dissociation process of split aptamer/VEGF(165) complexes was revealed, which was similar to that of the intact aptamer/VEGF(165). Besides, the dissociation rate constant (k(off)) of split aptamer/VEGF(165) was close to that of intact aptamer/VEGF(165), and the interaction force of split aptamer/VEGF(165) was higher than the force of intact aptamer/VEGF(165). It indicated that split aptamer also possessed high affinity with VEGF(165). The work can provide a new method for exploring the interaction of split aptamer/its targets at single-molecule level.