Lipid membranes: Biological inspiration for micro and nano encapsulation technologies, especially drug delivery

Our approach to biologically inspired materials and materials systems recognizes biology (at all scale levels) as a series of products that fulfill particular functions. It then links material composition and structure to function through properties and therefore attempts to bring mechanism to processes and functions of biology. As an example of this approach we have focused on the lipid bilayer membranes of blood cells, like erythrocytes and neutrophils, as a bioinspired material system for drug delivery leading to the creation of waxy, nano capsules called liposomes that can be triggered to release their drug by hyperthermia. Thus, while Nature's encapsulation technology provides the inspiration, the mechanism of drug release is non-natural. The necessary design parameters for the required functions of drug encapsulation, i.e. drug retention, circulation half life, and eventual thermally-triggered drug release, were obtained through extensive experimentation and modeling of artificial lipid vesicles by us and others, with much of the mechanical and thermomechanical properties, molecular exchange, and in vitro performance investigated by a direct micropipet manipulation technique. With respect to cancer chemotherapy, the unmet need for primary solid tumors is to deliver more drug to the tumor tissue thereby reducing the tumor size (debulking) while at the same time reducing toxic side effects. it is with these criteria in mind that we developed the temperature-triggered liposome for the treatment of solid tumors. This paper then, describes this liposome development and its performance in vivo, where, in some cases, the temperature-triggered release of drug directly in the blood stream and tumor resulted in complete tumor regression. What this example also shows is that through material property measurement and modeling, new insights into Nature's functions and designs can be discovered in a reverse engineering process from which new products can then be forward engineered to solve engineering and product problems in health, technology, and the environment.