Toward high yield synthesis of peptide–oligonucleotide chimera through a disulfide bridge: A simplified method for oligonucleotide activation

During the last decade, cell penetrating peptides (CPP) have been extensively used to mediate the cellular delivery of non-permeant biomolecules, including oligonucleotides (ONs). A covalent linkage between the CPP and the transported ON is required to mediate efficient cell internalization, and a disulfide bridge between the CPP and the ON has been shown to induce the most potent biological response. In this paper, we describe the activation. In a one step process of the sulfhydryl function from a synthon commercially available for ON synthesis. In addition, since the highly cationic nature of currently used CPP caused serious precipitation problems during the coupling step, we further improved the method by adsorbing the crude activated ON on an anion exchange matrix prior to specific peptide coupling.