Aptamer-Coupled Polymer-Grafted Fe₃O₄ Nanoparticles for Highly Efficient Isolation of Exosomes

Exosomes, the bioactive particles secreted by various cells, are essential in mediating cellular communication. However, their small size and the interference from non-exosome proteins present significant hurdles for their rapid and non-destructive capture and release. To overcome these obstacles, a promising strategy to efficiently and selectively isolate exosomes from mesenchymal stem cells (MSCs) is developed by using CD63 aptamer-conjugated magnetic nanoparticles (Fe₃O₄-Aptamer). The Fe₃O₄ nanoparticles are first modified by RAFT polymerization of N-(methacryloyloxy) succinimide and oligoethylene glycol methacrylate, and subsequently, CD63 aptamers are grafted onto the surface of nanoparticles to produce Fe₃O₄-Aptamer. These aptamer units act as a "lock and key" recognition with the CD63 proteins on exosomes, enabling specific binding to exosomes. The Fe₃O₄-Aptamer can efficiently capture exosomes in a conditioned medium, and be easily collected by an external magnetic field, facilitating the facile collection and multiple-cycle reuse of Fe₃O₄-Aptamer. By introducing the complementary sequence of the CD63 aptamer, the captured exosomes can be rapidly released from Fe₃O₄-Aptamer because of the stronger binding affinity between the complementary sequence and the aptamers. When utilized for exosome isolation, the exosome-capture and release efficiency of Fe₃O₄-Aptamer can achieve up to ca. 82.9% and 96.1%, respectively. Thus, Fe₃O₄-Aptamer offers a promising and facile strategy for the highly efficient isolation of exosomes.