Small-Angle X-ray Scattering Study of the Amphiphilic Bulk Nanostructure of Tetraalkylammonium Deep Eutectic Solvents.

Deep eutectic solvents (DESs) are low-melting mixtures, often prepared from a salt and a molecular hydrogen bond donor. Like ionic liquids, DESs that contain at least one sufficiently amphiphilic component can form bicontinuous nanostructures consisting of polar and nonpolar domains, although this has not been widely explored for many DES combinations. Here, the bulk nanostructures of DESs comprising tetraalkylammonium bromide salts (tetrabutylammonium bromide, tetraoctylammonium bromide, and methyltrioctylammonium bromide) with alkanols and alkanoic acids of systematically varied chain lengths (C2, C6, C8, and C10) as hydrogen bond donors have been studied. Small-angle X-ray scattering techniques were used to identify the relationship between the alkyl chain length and functionality of the hydrogen bond donor on the nature of the amphiphilic nanostructures formed. These findings demonstrated that the amphiphilic nanostructures of the DESs were not affected by the functional group on the hydrogen bond donor, with these nanostructures influenced primarily by both the absolute and relative alkyl chain lengths of the salt and hydrogen bond donor.

Regulating the structural polymorphism and protein corona composition of phytantriol-based lipid nanoparticles using choline ionic liquids.

Lipid-based lyotropic liquid crystalline nanoparticles (LCNPs) face stability challenges in biological fluids during clinical translation. Ionic Liquids (ILs) have emerged as effective solvent additives for tuning the structure of LCNP's and enhancing their stability. We investigated the effect of a library of 21 choline-based biocompatible ILs with 9 amino acid anions as well as 10 other organic/inorganic anions during the preparation of phytantriol (PHY)-based LCNPs, followed by incubation in human serum and serum proteins. Small angle X-ray scattering (SAXS) results show that the phase behaviour of the LCNPs depends on the IL concentration and anion structure. Incubation with human serum led to a phase transition from the inverse bicontinuous cubic (Q2) to the inverse hexagonal (H2) mesophase, influenced by the specific IL present. Liquid chromatography-mass spectrometry (LC-MS) and proteomics analysis of selected samples, including PHY control and those with choline glutamate, choline hexanoate, and choline geranate, identified abundant proteins in the protein corona, including albumin, apolipoproteins, and serotransferrin. The composition of the protein corona varied among samples, shedding light on the intricate interplay between ILs, internal structure and surface chemistry of LCNPs, and biological fluids.

Real-Time pH-Dependent Self-Assembly of Ionisable Lipids from COVID-19 Vaccines and In Situ Nucleic Acid Complexation.

Ionisable amino-lipid is a key component in lipid nanoparticles (LNPs), which plays a crucial role in the encapsulation of RNA molecules, allowing efficient cellular uptake and then releasing RNA from acidic endosomes. Herein, we present direct evidence for the remarkable structural transitions, with decreasing membrane curvature, including from inverse micellar, to inverse hexagonal, to two distinct inverse bicontinuous cubic, and finally to a lamellar phase for the two mainstream COVID-19 vaccine ionisable ALC-0315 and SM-102 lipids, occurring upon gradual acidification as encountered in endosomes. The millisecond kinetic growth of the inverse cubic and hexagonal structures and the evolution of the ordered structural formation upon ionisable lipid-RNA/DNA complexation are quantitatively revealed by in situ synchrotron radiation time-resolved small angle X-ray scattering coupled with rapid flow mixing. We found that the final self-assembled structural identity, and the formation kinetics, were controlled by the ionisable lipid molecular structure, acidic bulk environment, lipid compositions, and nucleic acid molecular structure/size. The implicated link between the inverse membrane curvature of LNP and LNP endosomal escape helps future optimisation of ionisable lipids and LNP engineering for RNA and gene delivery.

Small angle X-ray scattering investigation of ionic liquid effect on the aggregation behavior of globular proteins.

Globular proteins are well-folded model proteins, where ions can substantially influence their structure and aggregation. Ionic liquids (ILs) are salts in the liquid state with versatile ion combinations. Understanding the IL effect on protein behavior remains a major challenge. Here, we employed small angle X-ray scattering to investigate the effect of aqueous ILs on the structure and aggregation of globular proteins, namely, hen egg white lysozyme (Lys), human lysozyme (HLys), myoglobin (Mb), ß-lactoglobulin (ßLg), trypsin (Tryp) and superfolder green fluorescent protein (sfGFP). The ILs contain ammonium-based cations paired with the mesylate, acetate or nitrate anion. Results showed that only Lys was monomeric, whereas the other proteins formed small or large aggregates in buffer. Solutions with over 17 mol% IL resulted in significant changes in the protein structure and aggregation. The Lys structure was expanded at 1 mol% but compact at 17 mol% with structural changes in loop regions. HLys formed small aggregates, with the IL effect similar to Lys. Mb and ßLg mostly had distinct monomer and dimer distributions depending on IL type and IL concentration. Complex aggregation was noted for Tryp and sfGFP. While the anion had the largest ion effect, changing the cation also induced the structural expansion and protein aggregation.