Study of the influence of pH on the conformation of a modified aptamer to nucleolin protein

The search for agents for targeted delivery of anticancer drugs remains a crucial challenge for medicine. For this reason, DNA aptamers targeting cancer cell-specific proteins have medical use. At the same time, the additional fine-tuning of aptamer properties to lower affinity of aptamers for target cells that are not surrounding cancerous tissues makes the aptamers promising tools in clinical applications due to reduced immunogenicity and fewer side effects. One of the approaches is to use acidity disruption in cancer cells and tissues. In this work, aptamer AS1411 was modified to increase affinity for nucleolin by attaching a nucleotide sequence to its binding site to create a pH-sensitive linker. UV melting and fluorescence methods were employed to demonstrate that the conformation of the new aptamer depends on pH of the medium.