Biomaterial biotechnology using self-assembled lipid microstructures.

Lipids are a class of molecules which self-assemble into a variety of phase-dependent morphologies. We have employed self-assembled lipid microstructures in the development of a number of biomedical material applications. The blood substitute, liposome encapsulated hemoglobin, is being investigated for the in vivo delivery of hemoglobin without many of the inherent toxicities associated with the delivery of free hemoglobin. This investigation is currently focused on demonstrations of efficacy in stressed animal models and on the safety of administering this material in models of sepsis. The synthetic modification of phospholipids to include photopolymerizable moieties such as diacetylenes has resulted in the spontaneous self-assembly of a hollow microcylinder which we are investigating for the controlled release of growth factors in soft tissue regeneration. Self-assembled monolayers are also being explored for the ability to surface modify biomaterials for improved cell adhesion. Photolithographic techniques have been combined with monolayer deposition to fabricate coplanar patterns of cell adhesion and inhibiting moieties. This results in the ability to spatially control the adhesion of cells to biomaterial surfaces. These cell patterns can form the basis for understanding two- and three-dimensional cellular events on the biomaterial surface and for the fabrication of improved cell-based biocompatible surfaces. The spontaneous self-assembly of lipids to form structures of biotechnological interest presents a unique opportunity to exploit this class of molecules for biomaterial applications.