GOALI: Vesicle Dynamics: The Transition From Unilamellar to Multilamellar Structures

University Of California-Santa Barbara, Santa Barbara CA

Investigators

Abstract

0968105 - Leal Vesicle based home and personal care products constitute a multi-billion dollar business worldwide. Further, products that utilize vesicles for the encapsulation and transport of drugs or other chemical species offer an enormous potential that is only beginning to be exploited. Yet a fundamental understanding of what determines vesicle structure is lacking, and this is both extremely costly in terms of product stability, and limiting in the development of new and more effective encapsulation procedures. The research proposed here is a very significant first step toward addressing this deficiency for the very important class of cationic lipid bilayer vesicles. Such vesicles are observed to exist both in unilamellar and multilamellar ("onion") structures, with a transition from unilamellar to multilamellar structures sometimes occurring spontaneously over periods of hours or days. This project is aimed at understanding how and when the structure of vesicles may change (or be changed) from a single bilayer membrane to so-called "onion" structures involving multiple imbedded bilayers. Experiments will be done to correlate observations of vesicle structure, and how it may change with time, with measurements of the mechanical properties of the membrane. Membrane properties will be varied via different combinations of lipids/surfactants, and the total concentration of lipids will be changed to control the volume fraction of vesicles in the suspension. Vesicle structure will be studied primarily via Cryo-TEM imaging. Membrane properties will be determined via micropipette aspiration techniques using giant unilamellar vesicles. A theoretical basis will also be developed, using numerical simulation methods, for predicting the changes of vesicle structure, both from a molecular dynamics and continuum point of view. The combination of experiments and theory proposed here will therefore provide new insight into the relationship between the constituent make-up of bilayer membranes, their measurable mechanical properties, and the structure of corresponding vesicles. The proposed research is transformative as it is a first step in rationalizing the design of vesicles with control over structure with applications in both materials development, and potentially in drug delivery processes. Indeed, our industrial partner views this project as having the long term potential for changing their "research tactics in a revolutionary way". In addition, it quantifies the micropipette aspiration method for the measurement of membrane properties; and it improves the ability to theoretically describe vesicles via continuum-based models. Broader Impacts: The PhD student will benefit greatly from collaboration with Procter and Gamble via access to a broad range of materials, and facilities, beyond what is available at UCSB, as well as a level of insight about the industrial formulation and production of vesicles, that is simply not available in the open literature. The project also involves important outreach activities including: 1) the development (together with Todd Squires) of a UCSB freshman seminar (for non-science majors) on the science and engineering that goes into various food and personal care products, including those made from vesicles; and 2) funding to allow participation of the PI in the summer undergraduate and teacher intern programs sponsored by the MSERC program at UCSB. These programs are a fantastic opportunity for students involving 8-10 week individually mentored summer research projects, as well as weekly meetings with education staff to develop oral, visual and written communication skills.