(718g) Active DNA Olympic Hydrogels Driven By Topoisomerase Activity

Four decades ago, Pierre-Gilles de Gennes envisioned the possibility of synthesizing polymeric gels from topologically interlinked ring polymers (“Olympic gels”), rather than chemical or physical bonds. Despite long-standing interest in topological bonds across the fields of chemistry, nanotechnology, and polymer physics, the synthesis of Olympic gels has remained an enduring challenge for polymer chemists. In contrast, biological systems are equipped with a diverse repertoire of proteins that regulate DNA topology with precision that is beyond the reach of conventional polymer chemistry. Here, we harness the unique properties of topoisomerases to synthesize Olympic hydrogels formed by topologically interlinked DNA rings. Using dynamic light scattering microrheology (DLSμR) to probe the viscoelasticity of DNA topological networks, we show that topoisomerase II enables the facile preparation of active, ATP-driven Olympic hydrogels. The active Olympic hydrogels can be switched between liquid and solid states on demand, based solely on the catalytic activity of topoisomerase. Specifically, topoisomerase II can resolve topological links through phantom chain-like strand-passage reactions. Our DLSμR measurements enable us to interrogate the viscoelasticity of Olympic hydrogels over 7 decades in time, which reveals the hierarchical molecular relaxations that govern their dynamics. These molecular relaxations include the rapid bending fluctuations of the DNA double-helix, the intermediate time scale gel elasticity due to topological links, and the slow fluid relaxation of the hydrogel arising from topoisomerase-mediated strand passage reactions. Our results provide a versatile system for engineering switchable topological materials that may be broadly leveraged to model the impact of topological constraints and active dynamics in the physics of chromosomes and other polymeric materials.