Biomimetic design and performance of polymerizable lipids

Abstract

Bilayer lipid membranes (BLMs) have received significant attention over the past several decades because of their applications in biological and material sciences. BLMs consist of two amphiphilic lipid layers arranged with their hydrophilic head region exposed to the surrounding aqueous environment and hydrophobic domains in the core. In biology, lipid membranes confine and support the cell structure while selectively controlling the diffusion of ions and proteins between the intra- and extracellular matrix (ECM). Naturally derived lipid monomers spontaneously self-assemble to develop smart gateways that recognize and incorporate desired protein transporters or ion channels. BLMs are useful research models of lamellar lipid assemblies and associated protein receptors in cell membranes. The transport properties of lipid membranes can be tuned through careful consideration of the solution medium, transporter functionality, and pH, as well as other environmental conditions. BLMs are of particular interest in the design of biofunctional coatings, controlled release technologies, and biosensors; however, high-performance applications require lipid membranes to remain stable under harsh denaturing conditions. Accordingly, synthetic strategies are often proposed to increase the chemical and mechanical stability of lipid assemblies. The polymerization of self-assembled lipid structures is a strategy that results in robust biocompatible architectures, and diverse reactive functional groups are available for the synthesis of monomeric lipids. The selection of the polymerizable functionality and its precise location within the lipid assembly influences the ultimate supramolecular microstructure and polymerization efficiency. The biomimetic potential of polymerized lipids depends on the stability and robustness of the self-assembled membranes, and it is essential that the polymerizable functionality not disturb the amphiphilic nature of the lipid to maintain biocompatibility. Innovative applications are the motivational force for the development of durable polylipid compositions. Surface modification with biocompatible polylipids provides the opportunity for specific binding of biological molecules for applications as sensors or controlled release delivery vehicles. The ability to create stable lipid assemblies requires a comprehensive understanding of the mechanism of lipid polymerization in confined supramolecular geometries. The future is exciting as researchers begin to fully understand the morphology of polylipids in an effort to successfully produce naturally derived sustainable materials. In this Account, we highlight recent efforts to covalently stabilize lipid membranes and discuss emerging applications of mechanically robust self-assembled lipid architectures.