Aptamers with Self-Loading Drug Payload and pH-Controlled Drug Release for Targeted Chemotherapy.

Doxorubicin (DOX) is a common anti-tumor drug that binds to DNA or RNA via non-covalent intercalation between G-C sequences. As a therapeutic agent, DOX has been used to form aptamer-drug conjugates for targeted cancer therapy in vitro and in vivo. To improve the therapeutic potential of aptamer-DOX conjugates, we synthesized trifurcated Newkome-type monomer (TNM) structures with three DOX molecules bound through pH-sensitive hydrazone bonds to formulate TNM-DOX. The aptamer-TNM-DOX conjugate (Apt-TNM-DOX) was produced through a simple self-loading process. Chemical validation revealed that Apt-TNM-DOX stably carried high drug payloads of 15 DOX molecules per aptamer sequence. Functional characterization showed that DOX payload release from Apt-TNM-DOX was pH-dependent and occurred at pH 5.0, which reflects the microenvironment of tumor cell lysosomes. Further, Apt-TNM-DOX specifically targeted lymphoma cells without affecting off-target control cells. Aptamer-mediated cell binding resulted in the uptake of Apt-TNM-DOX into targeted cells and the release of DOX payload within cell lysosomes to inhibit growth of targeted lymphoma cells. The Apt-TNM-DOX provides a simple, non-toxic approach to develop aptamer-based targeted therapeutics and may reduce the non-specific side effects associated with traditional chemotherapy.