Aptamer-Based Targeted Delivery of Functional Nucleic Acids

Functional nucleic acid (NA)-based drugs have a broad range of applications since they allow the alteration and control of gene/protein expression patterns in cells. In principle, functional NAs need to be transported precisely and efficiently to target cells to guarantee both functionality and safety. Owing to their negative charges, it is difficult for natural NAs to cross the cell membrane composed of lipid bilayer and enter targeted cells. Worse still, the delivery of undirected functional NAs to nontargeted healthy cells and/or tissues would induce unpredictable adverse effects. Therefore, the precisely targeted delivery of functional NAs to specific cells/organs, particularly in extrahepatic sites, is required. Since aptamers can bind to various proteins on the cell surface with high specificity and selectivity, they can serve as the molecular recognition units to accurately bind target cells and subsequently enable the efficient delivery of cargo. In this perspective, we summarize the original, proof-of-concept aptamer-based strategies for the targeted delivery of functional NAs. A few specific examples are then discussed, followed by our perspectives on some of the challenges and opportunities that lie ahead.