Glycerol prevents dehydration in lipid cubic phases

Encapsulation of Aspartic Protease in Nonlamellar Lipid Liquid Crystalline Phases

Encapsulation of proteins within lipid inverse bicontinuous cubic phases (Q₂) has been widely studied for many applications, such as protein crystallization or drug delivery of proteins for food and pharmaceutical purposes. However, the use of the lipid sponge (L₃) phase for encapsulation of proteins has not yet been well explored. Here, we have employed a lipid system that forms highly swollen sponge phases to entrap aspartic protease (34 kDa), an enzyme used for food processing, e.g., to control the cheese-ripening process. Small-angle x-ray scattering showed that although the L₃ phase was maintained at low enzyme concentrations (≤15 mg/mL), higher concentration induces a transition to more curved structures, i.e., transition from L₃ to inverse bicontinuous cubic (Q₂) phase. The Raman spectroscopy data showed minor conformational changes assigned to the lipid molecules that confirm the lipid-protein interactions. However, the peaks assigned to the protein showed that the structure was not significantly affected. This was consistent with the higher activity presented by the encapsulated aspartic protease compared to the free enzyme stored at the same temperature. Finally, the encapsulation efficiency of aspartic protease in lipid sponge-like nanoparticles was 81% as examined by size-exclusion chromatography. Based on these results, we discuss the large potential of lipid sponge phases as carriers for proteins.

Improvement of lipidic bicontinuous cubic phases by the addition of a zwitterion with strong hydration ability and kosmotropicity

The water activity of lipidic bicontinuous cubic phases is successfully reduced by adding an imidazolium-based zwitterion with strong hydration ability and kosmotropicity.

Complex three-dimensional self-assembly in proxies for atmospheric aerosols

Aerosols are significant to the Earth’s climate, with nearly all atmospheric aerosols containing organic compounds that often contain both hydrophilic and hydrophobic parts. However, the nature of how these compounds are arranged within an aerosol droplet remains unknown. Here we demonstrate that fatty acids in proxies for atmospheric aerosols self-assemble into highly ordered three-dimensional nanostructures that may have implications for environmentally important processes. Acoustically trapped droplets of oleic acid/sodium oleate mixtures in sodium chloride solution are analysed by simultaneous synchrotron small-angle X-ray scattering and Raman spectroscopy in a controlled gas-phase environment. We demonstrate that the droplets contained crystal-like lyotropic phases including hexagonal and cubic close-packed arrangements of spherical and cylindrical micelles, and stacks of bilayers, whose structures responded to atmospherically relevant humidity changes and chemical reactions. Further experiments show that self-assembly reduces the rate of the reaction of the fatty acid with ozone, and that lyotropic-phase formation also occurs in more complex mixtures more closely resembling compositions of atmospheric aerosols. We suggest that lyotropic-phase formation likely occurs in the atmosphere, with potential implications for radiative forcing, residence times and other aerosol characteristics.

Nearly all atmospheric aerosols contain surface-active organic compounds; however, the nature of how they arrange remains poorly understood. Here, the authors show that fatty acids in atmospheric aerosol proxies self-assemble into highly ordered, viscous 3D nanostructures that undergo changes upon exposure to humidity and ozone.

Soft nanostructured films for directing the assembly of functional materials

Lipids are a class of biological small molecules with hydrophilic and hydrophobic constituents forming the structural membranes in cells. Over the past century an extensive understanding of lipid biology and biophysics has been developed illuminating lipids as an intricate, highly tunable, and hierarchical soft-matter system. In addition to serving as cell membrane models, lipids have been investigated as microphase separated structures in aqueous solutions. In terms of applications lipids have been realized as powerful structural motifs for the encapsulation and cellular delivery of genetic material. More recently, lipids have also revealed promise as thin film materials, exhibiting long-range periodic nano-scale order and tunable orientation. In this review we summarize the pertinent understanding of lipid nanostructure development in bulk aqueous systems followed by the current and potential perturbations to these results induced by introduction of a substrate. These effects are punctuated by a summary of our published results in the field of lipid thin films with added nucleic acids and key results introducing hard materials into lipid nanostructured substrates.

Control of Nanomaterial Self-Assembly in Ultrasonically Levitated Droplets

We demonstrate that acoustic trapping can be used to levitate and manipulate droplets of soft matter, in particular, lyotropic mesophases formed from self-assembly of different surfactants and lipids, which can be analyzed in a contact-less manner by X-ray scattering in a controlled gas-phase environment. On the macroscopic length scale, the dimensions and the orientation of the particle are shaped by the ultrasonic field, while on the microscopic length scale the nanostructure can be controlled by varying the humidity of the atmosphere around the droplet. We demonstrate levitation and in situ phase transitions of micellar, hexagonal, bicontinuous cubic, and lamellar phases. The technique opens up a wide range of new experimental approaches of fundamental importance for environmental, biological, and chemical research.

Aligned platinum nanowire networks from surface-oriented lipid cubic phase templates

Mesoporous metal structures featuring a bicontinuous cubic morphology have a wide range of potential applications and novel opto-electronic properties, often orientation-dependent. We describe the production of nanostructured metal films 1-2 microns thick featuring 3D-periodic 'single diamond' morphology that show high out-of-plane alignment, with the (111) plane oriented parallel to the substrate. These are produced by electrodeposition of platinum through a lipid cubic phase (Q(II)) template. Further investigation into the mechanism for the orientation revealed the surprising result that the Q(II) template, which is tens of microns thick, is polydomain with no overall orientation. When thicker platinum films are grown, they also show increased orientational disorder. These results suggest that polydomain Q(II) samples display a region of uniaxial orientation at the lipid/substrate interface up to approximately 2.8 ± 0.3 μm away from the solid surface. Our approach gives previously unavailable information on the arrangement of cubic phases at solid interfaces, which is important for many applications of Q(II) phases. Most significantly, we have produced a previously unreported class of oriented nanomaterial, with potential applications including metamaterials and lithographic masks.