Supramolecular oligo-thymine/melamine nanobridge-driven macroscopic engineering: reprogrammable hydrogels for multi-stimuli responsive architectures

The arbitrary, modular, and reprogrammable engineering of macroscopic objects by DNA interactions remains a challenge, despite the well-established use of DNA to drive constructs at nano/micro-scale. Moreover, achieving adaptive responsiveness in assembled architectures under dynamic environmental triggers has yet to be realized. In this study, we introduce the association of oligo-thymine strands (polyT) and melamine (MA), as a low-molecular-weight cofactor, into a supramolecular DNA duplex, termed polyT-MA nanobridge. This unique nanostructure exhibits responsiveness to five external stimuli, including temperature, DNA strand, small molecule, acidic pH, and alkaline pH. The polyT-MA nanobridge is developed as the dynamic crosslinking elements for constructing multi-stimuli responsive DNA hydrogels, which exhibit physiochemical properties changes (e.g., rigidity, thermal stability) and hydrogel-to-liquid phase transitions in response to the five external triggers. Notably, the assembly of macroscopic hydrogel blocks at millimeter scale (cubes in 5 × 5 × 5 mm dimensions) into diverse architectures, e.g., linear type, cross, P-shape, T-shape, or heteromorphy, is achieved by using the non-canonical supramolecular polyT-MA nanobridges. Sequential, dynamic, and selective disassembly of polyT-MA bridged hydrogel constructs is triggered by multiple external stimuli and the rearrangement of these separated individual cubes into other architectures in LEGO styles is presented. This study provides insights into the development of advanced materials and devices with reconfigurable architectures and functionalities for intelligent nanoengineering applications.