Aptamers as Molecular Smugglers

Abstract

Transporting therapeutics to their final destination within the body is still a challenge. For this purpose aptamers are particularly advantageous because of their ability to discriminate between different tissues or cell types. If a specific cell type or diseased tissue presents a characteristic marker like a protein, lipid, or sugar on its cell surface, aptamers can be selected that target exclusively this type of cells. The concentrated localization of an aptamer at defined tissues can also reduce the necessary dose of the therapeutic. Additionally, aptamers not only target cells specifically but are also able to carry a cargo inside the cell via receptor-mediated endocytosis for instance. After the internalization process the aptamer together with its cargo is located in vesicles inside the cell, in so-called endosomes. Receptors are normally recycled back to the cell surface or degraded and the aptamer with its cargo has to escape these vesicles to become operative. We here give a brief overview about the destiny of the internalized receptor with its cargo inside the cell, how the cargo can escape, and what type of cargos can be utilized.