I-motif-stapled and spacer-dependent multiple DNA nanostructures

Construction of stimuli-responsive biomaterials as one of the most fascinating research fields plays an important role in various applications including bioanalysis and drug delivery. Functional nucleic acids (e.g. G-quadruplex, i-motif and DNAzyme) have been widely adopted to fabricate stimuli-responsive biomaterials, attributed to its remarkable and editable functionality. Herein, we employed i-motifs to staple DNA building blocks and obtained multiple pH-switchable DNA structures. Through increasing the length of T-spacers between duplex segments and i-motif sequences, DNA building blocks assembled into primary superstructures from multimers, dimers to monomers, which were characterized elaborately by various techniques, electrophoresis, atomic force microscopy and circular dichroism spectroscopy. It was postulated that the spacer effect on the morphology of final DNA assemblies was derived from conformational constraint among adjacent DNA architectures. Our study not only establishes one new DNA-based method for preparing stimuli-responsive biomaterials, but also provides a significant clue that the DNA linkers (spacers) between different nucleic acid structures are capable of influencing the conformation and morphology of the final products.