"Theory and Molecular Simulation Studies of Macromolecular Soft Materials"
We develop and use theory and simulation techniques to understand molecular-level phenomena in macromolecular soft materials (polymers, DNA, proteins). The first part of my talk will focus on theory and simulation studies of polymer functionalized nanoparticles in polymer nanocomposites. Significant interest has grown around the ability to control spatial arrangement of nanoparticles in a polymer nanocomposite to engineer materials with target properties, e.g. metamaterials where the arrangement of nanoparticles dictates the resulting optical properties. One can tailor the inter-particle interactions and precisely control the assembly of the particles in the polymer matrix by functionalizing nanoparticle surfaces with ligands such as polymers, oligomers, DNA, and systematically tuning the composition, chemistry, molecular weight and grafting density of the ligands. We have developed an integrated self-consistent approach involving Polymer Reference Interaction Site Model (PRISM) theory and Monte Carlo simulations to study polymer grafted nanoparticles in polymer matrix. We have used this integrated theory-simulation approach to specifically understand the effect of heterogeneity, such as monomer chemistry, monomer sequence, and polydispersity, in the polymer functionalization on the conformations of the grafted polymers, the potential of mean force between functionalized nanoparticles, and the assembly of functionalized nanoparticles.
The second part will focus on use of molecular simulations to guide design of polymeric vectors for gene therapy. Gene therapy involves the delivery or transfection of therapeutic DNA into the genome of target cells. Viruses are effective at transfection but elicit dangerous immunogenic responses. Non-viral gene delivery agents while not as effective as viral vectors have a significant advantage of being non-immunogenic. Polycations have emerged as promising non-viral delivery agents due to their propensity to bind the polyanionic DNA backbone, neutralizing the negative charge of DNA backbone, and facilitating gene delivery. Recent experiments by our collaborator Emrick and his coworkers has shown that the architecture of poly-lysines affects, in a non-trivial manner , the efficiency of these polycations as transfection agents. Our work using molecular dynamics simulations using atomistic and coarse-grained models connects poly-L-lysine architecture to the strength of binding to DNA and explains many of the experimentally observed trends in transfection.
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