Caged Aptamers for Improved Cancer Imaging
Hypoxia-Activated PEGylated Conditional Aptamer/Antibody for Cancer Imaging with Improved Specificity.
J. Am. Chem. Soc. 2019;
21 January 2020 (online)
Aptamers and antibodies are widely used as probes in tumor imaging. Recognition of the tumor by aptamers is based on overexpression of their targets in cancer cells, not target exclusivity. Here, the authors present a strategy to increase the specificity of aptamers by designing a conditional aptamer. Upon exposure to the tumor microenvironment the aptamer is liberated and able to bind its target, thus leading to higher recognition selectivity.
The authors conjugated an azobenzene-linked PEG5000 chain as a steric blocking group to the aptamer XQ-2d. The azobenzene functions as a redox-sensitive caging unit. When exposed to hypoxia in the tumor microenvironment the azobenzene is cleaved, liberating the active aptamer close to the tumor. The authors demonstrate that this strategy can also be applied to antibodies.