Control of the stability and structure of liposomes by means of nanoparticles

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.The interaction of bilayer vesicles with hard nanoparticles is of great relevance to the field of nanotechnology, e.g., its impact on health and safety matters, and also as vesicles are important as delivery vehicles. In this work we describe hybrid systems composed of zwitterionic phospholipid vesicles (DPPC), which are below the phase transition temperature, and added silica nanoparticles (SiNPs) of much smaller size. The initial DPPC unilamellar vesicles, obtained by extrusion, are rather unstable and age but the rate of ageing can be controlled over a large time range by the amount of added SiNPs. For low addition they become destabilized whereas larger amounts of SiNPs enhance the stability largely as confirmed by dynamic light scattering (DLS). ζ-Potential and DSC measurements confirm the binding of the SiNPs onto the phospholipid vesicles, which stabilizes the vesicles against flocculation by rendering the ζ-potential more negative. This effect appears above a specific SiNP concentration, and is the result of the adsorption of the negatively charged nanoparticles onto the outer surface of the liposome leading to decorated vesicles as proven by cryogenic transmission electron microscopy (cryo-TEM). Small amounts of surface-adsorbed SiNPs initially lead to a bridging of vesicles thereby enhancing flocculation, while higher amounts render the vesicles much more negatively charged and thereby long-time stable. This stability has an optimum at neutral pH and for low ionic strength. Thus we show that the addition of the SiNPs is a versatile way to control the stability of gel-state phospholipid vesicles and also to modulate their surface structure in a systematic fashion. This is not only of importance for understanding the fundamental interaction between SiNPs and bilayer vesicles, but also with respect to using silica particles as formulation aids for phospholipid dispersions.DFG, GRK 1524, Self-Assembled Soft-Matter Nanostructures at Interface

Investigating the Permeability Evolution of Artificial Rock During Ductile and Brittle Deformation Under Pressurized Flow

The drilling of geothermal energy, CO2 sequestration, and wastewater injection all involve the pressurized flow of fluids through porous rock, which can cause deformation and fracture of the material. Despite the widespread use of these industrial methods, there is a lack of experimental data on the connection between the pore pressure rise, the deformation and permeability changes in real rock. In order to address this gap in the literature, this study developed an artificial rock material that can be deformed and fractured at low pressures. By controlling the porosity, permeability, and strength of the material during the sintering process, it is possible to mimic various types of rock. The artificial rock was designed to accommodate radial flow and deformation, allowing for the tracking of deformation by monitoring the flux and driving pressure and thus calculating the permeability changes under various pressure conditions. The study was able to examine the impact of both ductile and brittle deformation on the permeability during pressurized flow, which were captured by two models that were adjusted to this scenario. This study provides a link between pressurized flow, rock formation permeability and ductile to brittle deformation, that can constrain risk assessment to geothermal energy and CO

Fibrillar superstructure from extended nanotapes formed by a collagen-stimulating peptide

The nanostructure of a peptide amphiphile in commercial use in anti-wrinkle creams is investigated. The peptide contains a matrikine, collagen-stimulating, pentapeptide sequence. Selfassembly into giant nanotapes is observed and the internal structure was found to comprise bilayers parallel to the flat tape surfaces

Drug-loaded nanoparticles and supramolecular nanotubes formed from a volatile microemulsion with bile salt derivatives

The main objective of this study was to form nanoparticles of a model hydrophobic drug, celecoxib, from a volatile microemulsion stabilized by a bile salt derivative. Nanoparticles were obtained by conversion of the microemulsion nanodroplets with the dissolved drug into solid nanometric particles. The use of bile salt derivatives as the surfactants for the formation of a microemulsion enabled significantly higher loading of the drug in both the microemulsion and nanoparticles, compared with the native bile salt. In addition, superior stability of the particles was achieved with the bile salt derivatives, and drug crystallization was inhibited. Interestingly, differences in particle stability and crystallization inhibition were observed between two bile salt derivatives differing only by one hydroxyl group on the bile salt backbone, indicating the delicate balance of interactions in the system. For one of the derivatives, upon dispersion of the nanoparticles in water, they spontaneously arranged into well-defined elongated nanometric tubules as detected and attested by cryo-TEM. It was found that the drug present in nanoparticles induces formation of the nanotubes. This journal is © the Owner Societies

Integration of Gold Nanoparticles into Bilayer Structures via Adaptive Surface Chemistry

We describe the spontaneous incorporation of amphiphilic gold nanoparticles (Au NPs) into the walls of surfactant vesicles. Au NPs were functionalized with mixed monolayers of hydrophilic (deprotonated mercaptoundecanoic acid, MUA) and hydrophobic (octadecanethiol, ODT) ligands, which are known to redistribute dynamically on the NP surface in response to changes in the local environment. When Au NPs are mixed with preformed surfactant vesicles, the hydrophobic ODT ligands on the NP surface interact favorably with the hydrophobic core of the bilayer structure and guide the incorporation of NPs into the vesicle walls. Unlike previous strategies based on small hydrophobic NPs, the present approach allows for the incorporation of water-soluble particles even when the size of the particles greatly exceeds the bilayer thickness. The strategy described here based on inorganic NPs functionalized with two labile ligands should in principle be applicable to other nanoparticle materials and bilayer structures