428600 Engineering Biomimetic Self-Assembled Materials

Sunday, November 8, 2015
Exhibit Hall 1 (Salt Palace Convention Center)
Lorraine F. Leon, Institute for Molecular Engineering, University of Chicago, Chicago, IL

My research interests involve the design, characterization, and application of novel self-assembling materials.  In particular, I am interested in biomimetic systems in which carefully tuned molecular interactions create functional and responsive materials for applications ranging from nanoscale electronics to drug delivery.  Electrostatic interactions play a fundamental role in both creating spatially patterned interfaces and also creating separate polymer rich phases (complex coacervation) for both equilibrium and non-equilibrium processes, and yet are still largely misunderstood. Using rational design of peptides and polymers I intend to explore the role that these interactions play in compartmentalized delivery systems and as a dynamic templates to create hierarchical hybrid materials composed of organic and inorganic constructs.  My goal is to thoroughly understand the thermodynamic and kinetic processes driving the self-assembly of these materials and take them from the bench to their functional application. 

My postdoctoral work with Professor Matthew Tirrell (The Institute for Molecular Engineering, University of Chicago &Argonne National Laboratory) involves the design, characterization, and application of polyelectrolyte based materials.  We have explored the fundamentals of polyelectrolyte complexation using oppositely charged polypeptides and found methods of tuning the phase behavior of the resultant complex from liquid to solid by manipulating polymer chirality.  Additionally, we can stabilize these complexes at the nanoscale by forming micelles with either liquid or solid cores depending on their secondary structure, which provides unique self-assembly and degradation properties.  After carefully characterizing model systems, we designed polyelectrolyte complex micelles that contain therapeutically relevant charged molecules such as nucleic acids and peptides, specifically for the treatment of atherosclerotic lesions and cancer.  The modular nature of these assemblies enables the addition of a targeting ligand to increase the efficacy of delivering nucleic acids, creating polyelectrolyte complex micelles with a targeting ligand outside the corona of the micelle.  Our rationally designed micelles have successfully delivered miRNA inhibitors in vitro and are currently being tested in vivo. 

My graduate work with Professor Raymond Tu (Chemical Engineering Department, The City College of New York) involved the interfacial templating of inorganic materials using self-assembled peptides.   In nature, biological molecules form interfaces that assemble patterns of chemical functionality with exceptional precision. The role of dynamics during the assembly of biological molecules appears to be important for mineralization processes. Our work applied model sheet-forming peptides at interfaces to explore the dynamics of assembly in order to template mineral growth.  Thermodynamic analysis of structure formation with increasing surface pressure allowed us to understand the nature of self-assembly with iterative changes in the peptide sequence.  Additionally, we investigated the dynamics of the self-assembled state, where the organic phase switches between short- and long-range order as a function of surface pressure. This model system allowed us to explore the influence of electrostatic interactions on self-assembly and additionally the influence of short- and long-range order on the nucleation and growth of inorganic material.   This is in contrast to a system that starts with a well-ordered preformed template that defines the epitaxial growth of the mineral phase.  Versions of our model peptides are modified to include histidine in order to nucleate Au nanocrystals in both the short and long range ordered organic matrix showing that the phase behavior of the peptide influences the crystallinity and shape of the resultant nanocrystals.

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