Probing high affinity sequences of DNA aptamer against VEGF 165

Abstract

Vascular endothelial growth factor (VEGF 165) is a potent angiogenic mitogen commonly overexpressed in cancerous cells. It contains two main binding domains, the receptor-binding domain (RBD) and the heparin-binding domain (HBD). This study attempted to identify the specific sequences of the VEa5 DNA aptamer that exhibit high binding affinity towards the VEGF 165 protein by truncating the original VEa5 aptamer into different segments. Using surface plasmon resonance (SPR) spectroscopy for binding affinity analysis, one of the truncated aptamers showed a >200-fold increase in the binding affinity for HBD. This truncated aptamer also exhibited high specificity to HBD with negligible binding affinity for VEGF 121, an isoform of VEGF lacking HBD. Exposing colorectal cancer cells to the truncated aptamer sequence further confirmed the binding affinity and specificity of the aptamer to the target VEGF 165 protein. Hence, our approach of aptamer truncation can potentially be useful in identifying high affinity aptamer sequences for the biological molecules and targeting them as antagonist for cancer cell detection. © 2012 Kaur, Yung.