(5dx) Mechanistic Design of Functional Materials from Polyelectrolytes

Lapitsky, Y. - Presenter, University of Toronto

Recent advances in chemical product design, medicine and nanotechnology have ushered in a new age of ?smart? materials that respond to external stimuli such as changes in pH, ionic strength, temperature, and mechanical or electromagnetic perturbations. Polyelectrolytes provide acutely sensitive building blocks for these materials and are used in countless applications in foods, cosmetic product formulations, controlled release, biomaterials, medical imaging, sensors, fuel cells, water treatment and personal hygiene products. Despite their omnipresence in today's commercial and technological landscape, however, many uses of polyelectrolytes are limited by the incomplete understanding of their physicochemical properties and the design variables (both process and formulation) that control them. To this end, the overarching goals of my research are to (1) advance the understanding of their molecular, colloidal and macroscopic properties, and (2) to apply this understanding towards furthering their applications in controlled release devices, biomaterials and other chemical products.

My Ph.D. thesis work with Professor Eric Kaler at the University of Delaware focused on understanding the interactions between oppositely charged surfactants and polyelectrolytes and their relationship to the formation, structure and stability of surfactant-polyelectrolyte gels. We exploited these gel phases to form stimulus-responsive beads, capsules, fibers and coatings, and demonstrated their utility in the encapsulation and release of hydrophobic compounds. Additionally, to study the molecular interactions that underlie the properties of surfactant-polyelectrolyte mixtures, we proposed and investigated a simple calorimetric method for quantifying the strength and cooperativity of their binding. This method uses isothermal titration calorimetry (ITC) and provides an alternative to the conventional potentiometric methods, which rely on sensitive, custom-built electrodes that limit their use to only a few surfactant types.

In my postdoctoral research with Professor Molly Shoichet at the University of Toronto I have applied my experience in colloid, polymer and chemical engineering science to the mechanistic and quantitative design of polyelectrolyte-based biomaterials. Here, we exploited electrostatic, hydrophobic and antigen-antibody interactions towards the development of (1) cell-adhesive and cytocompatible fatty acid-biopolyelectrolyte scaffolds with highly-tunable degradation rates, (2) drug-binding hydrogels that provide quantitatively-predictable control over the drug release rates, and (3) quantitative guidelines for tuning the binding strength of self-assembled immunonanoparticles to cancer cells for targeted drug delivery.