Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder causing memory loss, language problems and behavioural disturbances. AD is associated with the accumulation of fibrillar amyloid-β (Aβ) and the formation of neurofibrillary tau tangles. Fibrillar Aβ itself represents a danger-associated molecular pattern, which is recognized by specific microglial receptors. One of the key players is formation of the NOD-, LRR-and pyrin domain-containing 3 (NLRP3) inflammasome, whose activation has been demonstrated in AD patient brains and transgenic animal models of AD. Here, we investigated whether Aβ oligomers or protofibrils that represent lower molecular aggregates prior to Aβ deposition are able to activate the NLRP3 inflammasome and subsequent interleukin-1 beta (IL-1β) release by microglia. In our study, we used Aβ preparations of different sizes: small oligomers and protofibrils of which the structure was confirmed by atomic force microscopy. Primary microglial cells from C57BL/6 mice were treated with the respective Aβ preparations and NLRP3 inflammasome activation, represented by caspase-1 cleavage, IL-1β production, and apoptosis-associated speck-like protein containing a CARD speck formation was analysed. Both protofibrils and low molecular weight Aβ aggregates induced a significant increase in IL-1β release. Inflammasome activation was confirmed by apoptosis-associated speck-like protein containing a CARD speck formation and detection of active caspase-1. The NLRP3 inflammasome inhibitor MCC950 completely inhibited the Aβ-induced immune response. Our results show that the NLRP3 inflammasome is activated not only by fibrillar Aβ aggregates as reported before, but also by lower molecular weight Aβ oligomers and protofibrils, highlighting the possibility that microglial activation by these Aβ species may initiate innate immune responses in the central nervous system prior to the onset of Aβ deposition. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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Structure of the self-assembled monolayers (SAMs) used to anchor phospholipid bilayers to surfaces affects the functional properties of the tethered bilayer membranes (tBLMs). SAMs of the same surface composition differing in the lateral distribution of the anchor molecule give rise to tBLMs of profoundly different defectiveness with residual conductance spanning 3 orders of magnitude. SAMs composed of anchors containing saturated alkyl chains, upon exposure to water (72 h), reconstruct to tightly packed clusters as deduced from reflection absorption infrared spectroscopy data and directly visualized by atomic force microscopy. The rearrangement into clusters results in an inability to establish highly insulating tBLMs on the same anchor layer. Unexpectedly, we also found that nanometer scale smooth gold film surfaces, populated predominantly with (111) facets, exhibit poor performance from the standpoint of the defectiveness of the anchored phospholipid bilayers, while corrugated (110) dominant surfaces produced SAMs with superior tethering quality. Although the detailed mechanism of cluster formation remains to be clarified, it appears that smooth surfaces favor lateral translocation of the molecular anchors, resulting in changes in functional properties of the SAMs. This work unequivocally establishes that conditions that favor cluster formation of the anchoring molecules in tBLM formation must be identified and avoided for the functional use of tBLMs in biomedical and diagnostic applications.

Controlling the interfacial behavior and properties of lipid liquid crystalline nanoparticles (LCNPs) at surfaces is essential for their application for preparing functional surface coatings as well as understanding some aspects of their properties as drug delivery vehicles. Here we have studied a LCNP system formed by mixing soy phosphatidylcholine (SPC), forming liquid crystalline lamellar structures in excess water, and glycerol dioleate (GDO), forming reversed structures, dispersed into nanoparticle with the surfactant polysorbate 80 (P80) as stabilizer. LCNP particle properties were controlled by using different ratios of the lipid building blocks as well as different concentrations of the surfactant P80. The LCNP size, internal structure, morphology, and charge were characterized by dynamic light scattering (DLS), synchrotron small-ange X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), and zeta potential measurements, respectively. With increasing SPC to GDO ratio in the interval from 35:65 to 60:40, the bulk lipid phase structure goes from reversed cubic micellar phase with Fd3m space group to reversed hexagonal phase. Adding P80 results in a successive shift toward more disorganized lamellar type of structures. This is also seen from cryo-TEM images for the LCNPs, where higher P80 ratios results in more extended lamellar layers surrounding the inner, more dense, lipid-rich particle core with nonlamellar structure. When put in contact with a solid silica surface, the LCNPs adsorb to form multilayer structures with a surface excess and thickness values that increase strongly with the content of P80 and decreases with increasing SPC:GDO ratio. This is reflected in both the adsorption rate and steady-state values, indicating that the driving force for adsorption is largely governed by attractive interactions between poly(ethylene oxide) (PEO) units of the P80 stabilizer and the silica surface. On cationic surface, i.e., silica modified with 3-aminopropltriethoxysilane (APTES), the slightly negatively charged LCNPs give rise to a very significant adsorption, which is relatively independent of LCNP composition. Finally, the dynamic thickness measurements indicate that direct adsorption of intact particles occurred on the cationic surface, while a slow buildup of the layer thickness with time is seen for the weakly interacting systems.

Lipid compositions with the ability to self-assemble into biocompatible nano-and mesostructured functional materials have many potential uses in modern medicine. By using twocomponent lipid systems, it is possible to tune the structure formation and related functional properties, e.g., the encapsulation and extended release of small molecules and peptides, by simply varying the ratio of the lipid building blocks. This is shown in detail for the binary phosphatidylcholine and diglyceride lipid systems, which are currently being used in multiple programs for the development of novel pharmaceuticals and marketed products.The ability of certain lipids to self-assemble into functional reversed-phase nonlamellar liquid crystal (LC) gels in contact with aqueous media, make such systems highly interesting for use as ambient responsive delivery systems using such functional features as bioadhesion, biodegradation, encapsulation, and controlled release.1 By exploiting the liquid-to-LC gel transition triggered on exposure of lipid solutions to aqueous media, it is possible to combine excellent in vivo encapsulation and extended release properties of some reversed LC gel phases, with the easy manufacturing and administration properties of relatively low-viscosity nonaqueous lipid solutions comprising small amounts of nonaqueous solvent. 1,2The most frequently used nonlamellar LC-forming lipid in drug delivery-related studies has been glycerol monooleate (GMO).3,4 At physiological conditions in excess water, GMO forms a bilayer-based bicontinuous cubic phase (V 2 ) with the Pn3m space group representing a three-dimensional network of hydrophilic and hydrophobic domains. Although a promising candidate for several applications, GMO-based LCs have been shown to exhibit a pronounced tendency to disrupt membrane structures, e.g., extensive hemolytic activity.5 Furthermore, the one-component GMO system has further limitations with respect to the drug delivery application in the difficulty of compensating for any phase changes caused by solubilizing drug compounds. 6 The use of a two or multicomponent system can typically alleviate this issue and can allow for compensation of unwanted phase changes by simply adjusting the ratio of the lipid building blocks. One example of such a system is the two-component unsaturated (e.g., dioleoyl) phosphatidylcholine (PC) and glycerol dioleate (GDO) system, where PC has a preference for the planar lamellar LC phase (L ¡ ) and GDO for the reversed liquid micellar phase (L 2 ). Between these extremes at full hydration reversed 2D hexagonal (H 2 ), reversed micellar cubic (I 2 ) with the Fd3m space group as well as two-and three-phase regions are formed. 711A recent study on the in vitro release of disodium fluorescein from soy PC (SPC)/GDO nonlamellar LCs has shown that the minimum of release (lowest release rates) can be found for compositions in the two-phase region between the H 2 and I 2 phases.1 Importantly, the observed release of both for small molecules 1 and peptides 2 from these phases ...