Assembly, Dynamics and Rheology of Colloidal Kinetoplast Clusters

About This Grant

Polymers are encountered in everyday life in products ranging from earbuds to clothing. Their ability to have specific properties (e.g. soft like the silicone in earbuds) arises from the chemical makeup of the molecules (how many carbons, hydrogens, oxygens etc.), their shape (e.g. polymers can have simple linear forms like spaghetti or be circular like a bracelet) and how mixtures of polymers fit together when mixed. There has been a growing trend to synthesize polymers with shapes beyond a simple linear form. Two-dimensional sheet-like polymers are an emerging new class of polymers. Research to date has focused on understanding synthesis of these novel polymers. A better understanding is needed of how to assemble them into complex structures. This project will study how 2-dimensional polymers can be made to assemble into various structures based upon the addition of a second molecular component. A range of added components (both linear polymers and small droplets) will be explored to develop rules for their assembly and to introduce new functionality. A key part of the research entails using specialized cameras and microscopes to take movies of single polymer molecules within these complicated mixtures. The project will train students to enter the workforce for advanced engineering topics combining single molecule manipulations and microfabrication. The project will provide research opportunities for high school teachers and undergraduates. Demonstration kits will be developed which can be used by school teachers to introduce concepts in molecular connectivity in materials. Discoveries from the project will impact the design of future high-performance polymer systems. Single molecule studies of DNA have provided new insights in the fields of soft matter and rheology. There is an emerging interest in polymers with more complex topologies and mixtures thereof which can translate to new material properties. The research team will study clusters formed from 2-dimensional catenated DNAs (called kinetoplasts or kDNA) when mixed with linear DNA or nanoemulsions. The team has recently established kinetoplasts from the Crithidia parasite as a model 2-dimensional polymer system. kDNA are soft, cup-shaped, cell-sized colloidal entities composed of thousands of circular DNA that are topologically interconnected like chainmail. The research program entails: 1) understanding kDNA clustering when mixed with linear DNA, 2) modulating kDNA clusters by using depletants with various properties and 3) studying the nonequilibrium dynamics of kDNA clusters in microfluidic devices. Single molecule fluorescence microscopy combined with bespoke microfluidic devices will be used to study these systems. This award will result in work at the front edge of fundamental studies of soft colloidal assembly/dynamics and rheology of 2D polymer assemblies. New insights will be gained into how 2D polymers can be assembled into superstructures through mixing with linear polymers or smaller colloidal nanoemulsions. The use of DNA of a model polymer will be expanded to two-dimensional colloidal “sheets” called kinetoplasts to understand how catenated DNA demix from linear DNA to form superstructures. The fundamental discoveries from this project will result in contributions to polymer physics texts and journal articles. Results from this work can lead to improved polymer processing, new materials and deeper mechanistic insights into 2D DNA rheology. The research will inform the design of DNA-based superstructures for possible use in biomedicine or “organo-DNA” materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.