DNA-Polymer Hybrids for Responsive and Repeatable Gating in Nanostructures

Deoxyribonucleic acid (DNA) is a remarkable molecule, responsible for cellular information storage, exhibiting unique chemical structure and interactions. These properties have enabled its applications in drug delivery, research tools, and novel materials, with many more potential applications as yet unrecognised. This project aims to develop responsive DNA-polymer hybrid materials capable of sensing and responding to environmental stimuli. These materials will capitalise on the dynamic properties of DNA, whilst utilising the favourable material properties of polymeric materials.<br/><br/>In this work, a DNA-polymer hybrid material was designed to form an aqueous hydrogel upon stimuli addition to generate a gate within a DNA-origami nanostructure to form a biological circuit board. The hydrogel was constructed from an acrylamide backbone, with pendant DNA functionality incorporated. DNA oligonucleotides with polymerisable acrydite handles were doped into the polymerisation reaction, resulting in sporadic incorporation of the DNA motifs.<br/><br/>The DNA motifs used were designed to gate the hydrogel structure under orthogonal stimuli. The stimuli investigated included: temperature, through a self-complementary sequence able to form inter-strand duplexes as lower temperatures; pH, via a i-motif formation involving Hoogsteen base pairing between two cytosine bases in which one is protonated below pH 5 with dissociation upon deprotonation above pH 7; and, a metal ion bridge, using silver ions to bridge two cytosine bases followed by addition of a cysteamine ligand to dissociate the strands. The stimuli chosen all generate transient intermolecular interactions and as such can be cycled repeatably, allowing for multiple opening and closing cycles of the gates without the need for replacing DNA-polymer components or damaging DNA-origami structures. By integrating the dynamic properties of DNA with the favourable characteristics of polymeric materials, these nanoscale systems offer a solution for the limitations of traditional electronic devices.