Dynamic concatenation leads to anomalous transport of ring DNA in concentrated solutions

Circular DNA polymers have been widely studied due to their biological relevance as well as the unique anomalous transport properties and viscoelasticity that concentrated solutions of ring DNA and their blends with linear DNA exhibit. We previously showed that in situ linearization and fragmentation of ring DNA via restriction enzymes leads to discrete thickening and thinning of DNA complex fluids and their composites with dextran. Here we use topoisomerase II to dynamically concatenate ring DNA, forming Olympic ring structures reminiscent of kinetoplasts. We visualize the fluorescent-labeled DNA rings comprising the concatemers and use particle tracking and differential dynamic microscopy to characterize the dynamics and time-varying size and shape of the actively linking and unlinking molecules. Beyond the insight our work provides to biological processes mediated by active restructuring of DNA, the complex fluids we engineer and study may have applications in the design of biocompatible active materials for cellular repair, toxin filtration and drug delivery.