Speaker:    Dr. Michael Cromer, School of Mathematics and Statistics, Rochester Institute of Technology

Abstract:    Wormlike micelles (WLMs) have emerged as promising drug delivery systems (DDS) due to their unique structural properties. Their ability to efficiently encapsulate drugs and achieve controlled release offers significant advantages over traditional methods. One key advantage of micelles as DDS is their responsiveness to stimuli. These "living" polymers undergo equilibrium breakage and growth through combinations. When subjected to stimuli, for example flow or changes in pH, the system is driven out of equilibrium, and the energy barrier for scission/recombination is modified. Experiments have revealed that, at high shear rates or changes in pH, micelles can undergo a structure transition from long, flexible chains to short, rod-like polymers. We develop a rheological model to approximate the nonlinear rheology of wormlike micelles using two constitutive models to represent the structural transition. Under flow, we hypothesize that stretching energy introduces a linear potential that decreases the rate of recombination and reduces the mean micelle length. Under pH changes, the electrostatic free energy accounts for repulsion due to presence of similarly charged ions. The increased repulsive force reduces the overall energy needed to break a chain. For successful cancer drug delivery, WLMs must remain elongated under flow until reaching the acidic tumor microenvironment, where they undergo a structural transition to shorter, rod-like micelles, signifying drug release.