(462h) Hybrid Synthesis of Bottlebrush DNA Polymers for Single-Molecule Rheology

Biopolymers with “bottlebrush” shapes are ubiquitous in biofluids ranging from synovial fluids to tear films. Bottlebrush polymers comprise linear polymer backbones with densely grafted side chains. This bottlebrush shape is associated with interesting fluid properties in confined geometries, such as high load bearing and pronounced lubrication. Despite correlations between bottlebrush shape and fluid performance, it remains unclear how the molecular dimensions of bottlebrush polymers influence material performance. Part of this uncertainty results from challenges in the direct, real-time visualization of synthetic and glycoprotein-based bottlebrush polymers. Conversely, direct visualization of DNA-based polymers is possible using single-molecule fluorescence microscopy.

Model bottlebrush DNA polymers with controlled molecular size and shape are prepared using a hybrid synthetic approach that combines bio-orthogonal “grafting to” and enzyme-based “grafting from” reactions. Reactions are monitored by gel electrophoresis to estimate graft density and length. The success of this hybrid synthetic approach is confirmed by atomic force microscopy (AFM) imaging and quantification of individual bottlebrush polymer molecules immobilized on surfaces. Using this new material platform, single-molecule dynamics of bottlebrush polymers are directly visualized at a fluid–solid interface. The insights provided by single-molecule measurements of bottlebrush DNA are anticipated to inform the design of novel therapeutics and advance understanding of molecular-scale transport phenomena.