Lipid Phase Research Articles

A 3D Quantification Technique for Liver Fat Fraction Distribution Analysis Using Dixon Magnetic Resonance Imaging.

This study presents a 3D quantification methodology for the distribution of liver fat fraction (LFF) through the utilization of Dixon MRI image analysis. The central aim is to offer a highly accurate and non-invasive means of evaluating liver fat content. The process involves the acquisition of In-phase and Water-phase images from a Dixon sequence. LFF maps are then meticulously computed voxel by voxel by dividing the Lipid Phase images by the In-phase images. Simultaneously, 3D liver contours are extracted from the In-phase images. These crucial components are seamlessly integrated to construct a comprehensive 3D-LFF distribution model. This technique is not limited to healthy livers but extends to those afflicted by hepatic steatosis. The results obtained demonstrate the remarkable effectiveness of this approach in both visualizing and quantifying liver fat content. It distinctly discerns patterns that differentiate between normal and steatotic livers. By harnessing Dixon MRI to extract the 3D structure of the liver, this method offers precise LFF assessments spanning the entirety of the organ, thereby holding great promise for the diagnosis of hepatic steatosis with remarkable effectiveness.

Phase behavior of phospholipid-based myelin figures influenced by pH

The study of the effects of external stimuli on lipidic mesophases may enable a better understanding of alterations in biomembranes and improve the design of multilayered lipid structures. Here we demonstrate the influence of pH on the formation of elongated multilamellar assemblies, known as myelin figures (MFs). Polarized light microscopy allowed us to follow the growth process and thermal stability of phosphatidylcholine-based MFs. Our results reveal that the dimensions of these cylindrical microstructures change depending on the initial pH of the aqueous phase required for the self-assembly of lipids into MFs. Furthermore, we have confirmed the significant strength of the association between pH and characteristic parameters of MFs using Spearman’s rank correlation tests. Also, we have shown that one- and two-photon fluorescence microscopy can reveal the morphological changes that occur in MFs resulting from the lipid phase transition. These findings indicate the feasibility of using non-destructive methods to gain insight into liquid crystalline properties of biologically relevant multilamellar lipid structures in a wide pH range.

Metabolic Profiling Analysis Uncovers the Role of Carbon Nanoparticles in Enhancing the Biological Activities of Amaranth in Optimal Salinity Conditions

Enhancing the productivity and bioactivity of high-functional foods holds great significance. Carbon nanoparticles (CNPs) have a recognized capacity for boosting both plant growth and the efficacy of primary and secondary metabolites. Furthermore, while salinity diminishes plant growth, it concurrently amplifies the production of phytomolecules. To ensure the robust and sustainable production of nutritious food, it becomes essential to elevate biomolecule yield without compromising plant growth. Here, we assessed the CNPs priming on plant performance and metabolites of the glycophyte amaranth (Amaranthus hypochondriacus) sprouts at the threshold salinity (25 mM NaCl; i.e., salinity that does not reduce growth but enhances the metabolites of that plant). We measured growth parameters, pigment levels, and primary (carbohydrates, amino acids, organic acids, fatty acids) and secondary metabolites (phenolics, flavonoids, tocopherols). CNP priming significantly improved biomass accumulation (fresh and dry weight) and primary and secondary metabolites of amaranth sprouts. Increased photosynthetic pigments can explain these increases in photosynthesis. Enhanced photosynthesis induced carbohydrate production, providing a C source for producing bioactive primary and secondary metabolites. The priming effect of CNPs further enhanced the accumulation of essential amino acids, organic acids, unsaturated fatty acids, tocopherols, and phenolics at threshold salinity. The increase in bioactive metabolites under threshold salinity can explain the CNP priming impact on boosting the antioxidant activities (FRAP, DPPH, anti-lipid peroxidation, superoxide-anion-scavenger, hydroxyl-radical-scavenger, Fe-chelating and chain-breaking activity in aqueous and lipid phases) and antimicrobial activities against Gram-positive and Gram-negative bacteria and fungi. Overall, this study suggested that threshold salinity and CNP priming could be useful for enhancing amaranth sprouts’ growth and nutritional quality.

Cryo-EM elucidates the uroplakin complex structure within liquid-crystalline lipids in the porcine urothelial membrane

The urothelium, a distinct epithelial tissue lining the urinary tract, serves as an essential component in preserving urinary tract integrity and thwarting infections. The asymmetric unit membrane (AUM), primarily composed of the uroplakin complex, constitutes a critical permeability barrier in fulfilling this role. However, the molecular architectures of both the AUM and the uroplakin complex have remained enigmatic due to the paucity of high-resolution structural data. In this study, we utilized cryo-electron microscopy to elucidate the three-dimensional structure of the uroplakin complex within the porcine AUM. While the global resolution achieved was 3.5 Å, we acknowledge that due to orientation bias, the resolution in the vertical direction was determined to be 6.3 Å. Our findings unveiled that the uroplakin complexes are situated within hexagonally arranged crystalline lipid membrane domains, rich in hexosylceramides. Moreover, our research rectifies a misconception in a previous model by confirming the existence of a domain initially believed to be absent, and pinpointing the accurate location of a crucial Escherichia coli binding site implicated in urinary tract infections. These discoveries offer valuable insights into the molecular underpinnings governing the permeability barrier function of the urothelium and the orchestrated lipid phase formation within the plasma membrane.

Analysis of Phase Heterogeneity in Lipid Membranes Using Single-Molecule Tracking in Live Cells.

In live cells, the plasma membrane is composed of lipid domains separated by hundreds of nanometers in dynamic equilibrium. Lipid phase separation regulates the trafficking and spatiotemporal organization of membrane molecules that promote signal transduction. However, visualizing domains with adequate spatiotemporal accuracy remains challenging because of their subdiffraction limit size and highly dynamic properties. Here, we present a single lipid-molecular motion analysis pipeline (lipid-MAP) for analyzing the phase heterogeneity of lipid membranes by detecting the instantaneous velocity change of a single lipid molecule using the excellent optical properties of nanoparticles, high spatial localization accuracy of single-molecule localization microscopy, and separation capability of the diffusion state of the hidden Markov model algorithm. Using lipid-MAP, individual lipid molecules were found to be in dynamic equilibrium between two statistically distinguishable phases, leading to the formation of small (∼170 nm), viscous (2.5× more viscous than surrounding areas), and transient domains in live cells. Moreover, our findings provide an understanding of how membrane compositional changes, i.e., cholesterol and phospholipids, affect domain formation. This imaging method can contribute to an improved understanding of spatiotemporal-controlled membrane dynamics at the molecular level.

The effect of intravenous lipid emulsion (ILE) on the pharmacokinetic/toxicokinetic dispositions of ivermectin and carprofen in rabbits.

Intravenous lipid emulsion (ILE) has been widely used as an effective antidote in both veterinary and human medicine for the treatment of acute intoxications caused by drugs and pesticides with high lipid solubility. This study was conducted to investigate the effect of ILE co-administration on the kinetic dispositions of ivermectin (IVM) and carprofen (CRP) following intravenous bolus administration at subtoxic doses in rabbits.Twenty-four male New Zealand rabbits weighing 2.78 ± 0.2kg were used in this study. Rabbits were divided into four groups (Group 1: IVM and Group 2: IVM + ILE or Group 3: CRP and Group 4: CRP + ILE), each group consisting of 6 animals. In the IVM study, Group 1 received IVM (0.6mg/kg) alone while Group 2 received IVM (0.6mg/kg) and ILE (2.5ml/kg). In the CRP study, Group 3 received CRP (12mg/kg) alone while Group 4 received CRP (12mg/kg) and ILE (2.5ml/kg). In both drug groups, ILE was administered 3 times as an i.v. bolus at the 10th min and repeated 4th and 8th h after the drug administration. Blood samples were collected from the auricular vein at various times after drug administration. The drug concentrations in plasma samples were determined by high-pressure liquid chromatography. Kinetic parameters were calculated using a non-compartmental model for both CRP and IVM.The C0 and area under the concentration-time curve from zero up to ∞ (AUC0-∞) values were significantly greater with ILE co-administration (2136ng/ml and 360.84ng.d/ml) compared to the IVM alone (1340.63ng/ml and 206ng.d/ml), respectively. Moreover, the volume of distribution (Vdss) and clearance (Cl) of IVM were reduced by approximately 42% and 46% with ILE co-administration compared to IVM alone resulting in a reduction of the distribution and slower elimination, respectively. Similar differences in C0, and Vdss values were also observed in CRP with ILE co-administration compared to CRP alone. ILE co-administration changed significantly the kinetic profile of both IVM and CRP in rabbits, supporting the lipid sink theory in which highly lipid-soluble compounds are absorbed into the lipid phase of plasma from peripheral organs such as the heart and brain affected by the acute toxicity of the compounds.

Understanding the free-energy landscape of phase separation in lipid bilayers using molecular dynamics

Liquid-liquid phase separation inside the cell often results in biological condensates that can critically affect cell homeostasis. Such phase separation events occur in multiple parts of cells, including the cell membranes, where the “lipid raft” hypothesis posits the formation of ordered domains floating in a sea of disordered lipids. The resulting lipid domains often have functional roles. However, the thermodynamics of lipid phase separation and their resulting mechanistic effects on cell function and dysfunction are poorly understood. Understanding such complex phenomena in cell membranes, with their diverse lipid compositions, is exceptionally difficult. For these reasons, simple model systems that can recapitulate similar behavior are widely used to study this phenomenon. Despite these simplifications, the timescale and length scales of domain formation pose a challenge for molecular dynamics (MD) simulations. Thus, most MD studies focus on spontaneous lipid phase separation—essentially measuring the sign (but not the amplitude) of the free-energy change upon separation—rather than directly interrogating the thermodynamics. Here, we propose a proof-of-concept pipeline that can directly measure this free energy by combining coarse-grained MD with enhanced sampling protocols using a novel collective variable. This approach will be a useful tool to help connect the thermodynamics of phase separation with the mechanistic insights already available from MD simulations.

Cationic Proteins Rich in Lysine Residue Trigger Formation of Non-bilayer Lipid Phases in Model and Biological Membranes: Biophysical Methods of Study.

Cationic membrane-active toxins are the most abundant group of proteins in the venom of snakes and insects. Cationic proteins such as cobra venom cytotoxin and bee venom melittin are known for their pharmacological reactions including anticancer and antimicrobial effects which arise from the toxin-induced alteration in the dynamics and structure of plasma membranes and membranes of organelles. It has been established that these cationic toxins trigger the formation of non-bilayer lipid phase transitions in artificial and native mitochondrial membranes. Remarkably, the toxin-induced formation of non-bilayer lipid phase increases at certain conditions mitochondrial ATP synthase activity. This observation opens an intriguing avenue for using cationic toxins in the development of novel drugs for the treatment of cellular energy deficiency caused by aging and diseases. This observation also warrants a thorough investigation of the molecular mechanism(s) of lipid phase polymorphisms triggered by cationic proteins. This article presents a review on the application of powerful biophysical methods such as resonance spectroscopy (31P-, 1H-, 2H-nuclear magnetic resonance, and electron paramagnetic resonance), luminescence, and differential scanning microcalorimetry in studies of non-bilayer lipid phase transitions triggered by cationic proteins in artificial and biological membranes. A phenomenon of the triggered by cationic proteins the non-bilayer lipid phase transitions occurring within 10-2-10-11s is discussed in the context of potential pharmacological applications of cationic proteins. Next to the ATP dimer is an inverted micelle made of cardiolipin that serves as a vehicle for the transport of H+ ions from the intra-crista space to the matrix. It is proposed that such inverted micelles are triggered by the high density of H+ ions and the cationic proteins rich in lysine residue which compete with the conserved lysine residues of the ATP synthase rotor for binding to cardiolipin in the inner mitochondrial membrane and perturb the bilayer lipid packing of cristae. Phospholipids with a blue polar head represent cardiolipin and those with a red polar head represent other phospholipids found in the crista membrane.

Interfacial Aβ fibril formation is modulated by the disorder-order state of the lipids: The concept of the physical environment as amyloid inductor in biomembranes

The behavior of amphiphilic molecules such as lipids, peptides and their mixtures at the air/water interface allow us to evaluate and visualize the arrangement formed in a confined and controlled surface area. We have studied the surface properties of the zwitterionic DPPC lipid and Aβ(1–40) amyloid peptide in mixed films at different temperatures (from 15 to 40 °C). In this range of temperature the surface properties of pure Aβ(1–40) peptide remained unchanged, whereas DPPC undergoes its characteristic liquid-expanded → liquid-condensed bidimensional phase transition that depends on the temperature and lateral pressure. This particular property of DPPC makes it possible to dynamically study the influence of the lipid phase state on amyloid structure formation at the interface in a continuous, isothermal and abrupt change on the environmental condition. As the mixed film is compressed the fibril-like structure of Aβ(1–40) is triggered specifically in the liquid-expanded region, independently of temperature, and it is selectively excluded from the well-visible liquid condensed domains of DPPC. The Aβ amyloid fibers were visualized by using BAM and AFM and they were Thio T positive. In mixed DPPC/Aβ(1–40) films the condensed domains (in between 11 mN/m to 20 mN/m) become irregular probably due to the fibril-like structures is imposing additional lateral stress sequestering lipid molecules in the surrounding liquid-expanded phase to self-organize into amyloids.

Impact of the lipid phase composition and state on the in vitro digestibility and chlorophyllin bioaccessibility of W1/O/W2 emulsions into whole milk

Water-in-oil-in-water (W1/O/W2) emulsions offer the potential to deliver hydrophilic bioactive compounds into foods, yet their application remains limited due to their instability. Thus, the impact of lipid phase composition and state on the colloidal stability, in vitro lipid digestibility and chlorophyllin (CHL) bioaccessibility of W1/O/W2 emulsions before and after incorporation into whole milk was studied. Medium-chain triglyceride oil (MCT) was used as a liquid lipid phase and MCT with glyceryl stearate (GS) or pure hydrogenated palm oil (HPO) as gelled lipid phases. The lipid phase composition was crucial to forming W1/O/W2 emulsions. MCT or MCT+GS allowed the successful formation of W1/O/W2 emulsions, being more stable upon gastric conditions those formulated with MCT+GS than pure MCT. In contrast, the use of HPO led to phase separation, which was maintained after the gastric conditions. Regarding their lipid digestibility, W1/O/W2 emulsions formulated with MCT or MCT+GS were fully digested, whereas only 40% of the lipid was digested using HPO. In accordance, the CHL bioaccessibility was higher using MCT or MCT+GS than HPO. When co-digested with whole milk, the colloidal stability and lipid digestibility of the W1/O/W2 emulsions with MCT or MCT+GS were not altered, whereas the W1/O/W2 emulsion-HPO showed enhanced colloidal stability and lipid digestibility (57.71 ± 3.06%), due to the surface-active properties of milk protein. The present study provides useful information to develop stable functional foods enriched with hydrophilic bioactive compounds by using W1/O/W2 emulsions.

Wound-response jasmonate dynamics in the primary vasculature.

The links between wound-response electrical signalling and the activation of jasmonate synthesis are unknown. We investigated damage-response remodelling of jasmonate precursor pools in the Arabidopsis thaliana leaf vasculature. Galactolipids and jasmonate precursors in primary veins from undamaged and wounded plants were analysed usingMS-based metabolomics and NMR. In parallel, DAD1-LIKE LIPASEs (DALLs), which control the levels of jasmonate precursors in veins, were identified. A novel galactolipid containing the jasmonate precursor 12-oxo-phytodienoic acid (OPDA) was identified in veins: sn-2-O-(cis-12-oxo-phytodienoyl)-sn-3-O-(β-galactopyranosyl) glyceride (sn-2-OPDA-MGMG). Lower levels of sn-1-OPDA-MGMG were also detected. Vascular OPDA-MGMGs, sn-2-18:3-MGMG and free OPDA pools were reduced rapidly in response to damage-activated electrical signals. Reduced function dall2 mutants failed to build resting vascular sn-2-OPDA-MGMG and OPDA pools and, upon wounding, dall2 produced less jasmonoyl-isoleucine (JA-Ile) than the wild-type. DALL3 acted to suppress excess JA-Ile production after wounding, whereas dall2 dall3 double mutants strongly reduce jasmonate signalling in leaves distal to wounds. LOX6 and DALL2 function to produce OPDA and the non-bilayer-forming lipid sn-2-OPDA-MGMG in the primary vasculature. Membrane depolarizations trigger rapid depletion of these molecules. We suggest that electrical signal-dependent lipid phase changes help to initiate vascular jasmonate synthesis in wounded leaves.

A versatile approach to high-density microcrystals in lipidic cubic phase for room-temperature serial crystallography.

Serial crystallography has emerged as an important tool for structural studies of integral membrane proteins. The ability to collect data from micrometre-sized weakly diffracting crystals at room temperature with minimal radiation damage has opened many new opportunities in time-resolved studies and drug discovery. However, the production of integral membrane protein microcrystals in lipidic cubic phase at the desired crystal density and quantity is challenging. This paper introduces VIALS (versatile approach to high-density microcrystals in lipidic cubic phase for serial crystallography), a simple, fast and efficient method for preparing hundreds of microlitres of high-density microcrystals suitable for serial X-ray diffraction experiments at both synchrotron and free-electron laser sources. The method is also of great benefit for rational structure-based drug design as it facilitates in situ crystal soaking and rapid determination of many co-crystal structures. Using the VIALS approach, room-temperature structures are reported of (i) the archaerhodopsin-3 protein in its dark-adapted state and 110 ns photocycle intermediate, determined to 2.2 and 1.7 Å, respectively, and (ii) the human A2A adenosine receptor in complex with two different ligands determined to a resolution of 3.5 Å.

An Overview of Lutein in the Lipid Membrane.

Lutein, zeaxanthin, and meso-zeaxanthin (a steroisomer of zeaxanthin) are macular pigments. They modify the physical properties of the lipid bilayers in a manner similar to cholesterol. It is not clear if these pigments are directly present in the lipid phase of the membranes, or if they form complexes with specific membrane proteins that retain them in high amounts in the correct place in the retina. The high content of macular pigments in the Henle fiber layer indicates that a portion of the lutein and zeaxanthin should not only be bound to the specific proteins but also directly dissolved in the lipid membranes. This high concentration in the prereceptoral region of the retina is effective for blue-light filtration. Understanding the basic mechanisms of these actions is necessary to better understand the carotenoid-membrane interaction and how carotenoids affect membrane physical properties-such as fluidity, polarity, and order-in relation to membrane structure and membrane dynamics. This review focuses on the properties of lutein.

Enhanced stability and skin permeation of ibuprofen-loaded solid lipid nanoparticles based binary solid lipid matrix: Effect of surfactant and lipid compositions

HypothesisThe type of emulsifier selected has an impact on the physicochemical properties of solid lipid nanoparticles (SLNs). This study was designed to compare the effects of emulsifiers on the physicochemical properties and in vitro skin performance of SLNs prepared from a binary mixture of Softisan® 378 (S378) and cetyl palmitate (CP) to those of SLNs prepared from only CP and S378. ExperimentsSLNs were prepared from CP, S378, or a binary mixture of CP and S378 (1:1 w/w) as the lipid phase and stabilized with Tego®Care 450 (TG450) or poloxamer 188 (P188) containing 1.0% w/w ibuprofen loading. The physicochemical properties including the particle size, polydispersity index (PDI), zeta potential (ZP), encapsulation efficiency (E.E.), crystallinity (%CI), and polymorphism were determined after production and after storage for 180 days under different conditions. In addition, in vitro drug release and permeation through human skin was studied after production and storage at room temperature for 180 days. FindingThe particle sizes of ibuprofen-loaded SLNs (IBSLNs) stabilized with P188 (IBSLN-P188) were smaller than those of SLNs stabilized with TG450 (IBSLN-TG450) (p < 0.05). After 180 days, the particle sizes of the IBSLNs were slightly increased compared to those at the initial time but were <250 nm. The IBSLN-TG450 sample showed a higher %CI than IBSLN-P188 prepared with similar propotions of CP and S378, and ibuprofen crystals were observed in the IBSLN1-TG450 sample after storage at 4 °C for 180 days. Based on the result of the in vitro release study and the in vitro skin permeation test, the addition of S378 into the CP-matrix modified ibuprofen release and skin permeation both permeated ibuprofen through the epidermis and retained ibuprofen in the epidermis. In addition, the storage time affected the release and skin permeation of ibuprofen from the SLNs, which depended on the composition of the IBSLNs.

Non-bilayer Lipid Phases Modulate the Structure and Functions of Mitochondrial Membranes: Pharmacological Relevance

Non-bilayer Lipid Phases Modulate the Structure and Functions of Mitochondrial Membranes: Pharmacological Relevance

Viscosity-Sensitive Membrane Dyes as Tools To Estimate the Crystalline Structure of Lipid Bilayers.

Lipid membranes are crucial for cellular integrity and regulation, and tight control of their structural and mechanical properties is vital to ensure that they function properly. Fluorescent probes sensitive to the membrane's microenvironment are useful for investigating lipid membrane properties; however, there is currently a lack of quantitative correlation between the exact parameters of lipid organization and a readout from these dyes. Here, we investigate this relationship for "molecular rotors", or microviscosity sensors, by simultaneously measuring their fluorescence lifetime to determine the membrane viscosity, while using X-ray diffraction to determine the membrane's structural properties. Our results reveal a phase-dependent correlation between the membrane's structural parameters and mechanical properties measured by a BODIPY-based molecular rotor, giving excellent predictive power for the structural descriptors of the lipid bilayer. We also demonstrate that differences in membrane thickness between different lipid phases are not a prerequisite for the formation of lipid microdomains and that this requirement can be disrupted by the presence of line-active molecules. Our results underpin the use of membrane-sensitive dyes as reporters of the structure of lipid membranes.

Ethosome Containing Ceramide as a Skin Carrier of Active Ingredients.

Numerous formulations have been utilized in the cosmetic and pharmaceutical industries to effectively deliver bioactive ingredients. We selected a well-known liposomal formulation of bilayer lipid vesicles composed of ceramide NP. Ethosomes contain hydrophilic vanillic acid or lipophilic α-bisabolol, and their physicochemical properties were evaluated. Vanillic acid is encapsulated in the aqueous core while α-bisabolol is engaged with the lipid phase. The formulation was prepared by the high-pressure homogenization method at 800 bar for 5 min. The particle size, polydispersity index and zeta potential of the ethosome dispersion were analyzed by dynamic light scattering. In order to measure the skin absorption efficiency from artificial skin, an in vitro assay was performed using the Franz diffusion cell method for 24 hours. In addition, ultracentrifuges for encapsulation efficiency, dialysis membranes for active ingredient release, and low-temperature transmission electron microscopy (TEM) to evaluate the morphology of vesicles were utilized. The particle size of the ethosome containing ceramide NP and vanillic acid was in the range of 80 ~ 130 nm, whereas the particle size of the ethosome containing ceramide NP and α-bisabolol was 150 ~ 170 nm. In the vanillic acid-containing ethosome, increasing the amount of ceramide NP decreased the particle size, whereas the size of the α-bisabolol ethosome did not change. The stability of the prepared ethosome did not change significantly for 4 weeks at 25°C, 4°C, and 45°C. The skin absorption efficiency of ceramide NP and vanillic acid-containing ethosome was increased by about 15% compared to the control group, whereas the ethosome containing α-bisabolol and ceramide NP showed slightly higher skin absorption efficiency than the control group. In addition, encapsulation efficiency evaluation, active ingredient release measurement and cryo-TEM were taken. Based on the results of these studies, we suggest that ethosome formulations containing ceramide NP can be widely used in the cosmetic industry together with other cosmetic formulations.

Imaging Giant Vesicle Membrane Domains with a Luminescent Europium Tetracycline Complex.

Microdomains in lipid bilayer membranes are routinely imaged using organic fluorophores that preferentially partition into one of the lipid phases, resulting in fluorescence contrast. Here, we show that membrane microdomains in giant unilamellar vesicles (GUVs) can be visualized with europium luminescence using a complex of europium III (Eu3+) and tetracycline (EuTc). EuTc is unlike typical organic lipid probes in that it is a coordination complex with a unique excitation/emission wavelength combination (396/617 nm), a very large Stokes shift (221 nm), and a very narrow emission bandwidth (8 nm). The probe preferentially interacts with liquid disordered domains in GUVs, which results in intensity contrast across the surface of phase-separated GUVs. Interestingly, EuTc also alters GM1 ganglioside partitioning. GM1 typically partitions into liquid ordered domains, but after labeling phase-separated GUVs with EuTc, cholera toxin B-subunit (CTxB), which binds GM1, labels liquid disordered domains. We also demonstrate that EuTc, but not free Eu3+ or Tc, significantly reduces lipid diffusion coefficients. Finally, we show that EuTc can be used to label cellular membranes similar to a traditional membrane probe. EuTc may find utility as a membrane imaging probe where its large Stokes shift and sharp emission band would enable multicolor imaging.

Synthesis and characterization of liposomes encapsulating silver nanoprisms obtained by millifluidic-based production for drug delivery

Silver nanoprisms (SNPs) have attracted significant attention due to their surface plasmon resonance behaviour, which is strongly dependent on their size and shape. The enhanced light absorption and scattering capacity of SNPs, make them a promising candidate system for non-invasive imaging and drug delivery in nanoparticle-assisted diagnostics and therapy. However, systemic administration of silver nanoparticles (AgNPs) at high concentrations may result in toxic side-effects, arising from non-targeted bio-distribution. These drawbacks could be mitigated by employing liposomes as carriers for AgNPs. However, there is a lack of systematic studies on production and subsequent physico-chemical characterisation of liposomal systems encapsulating SNPs. The present study therefore investigated the synthesis of liposomes encapsulating SNPs (Lipo/SNPs) using a continuous-flow millimetre-scale reactor, whereby liposome formation was governed by a solvent exchange mechanism. An aqueous phase and an ethanolic lipid phase were conveyed through two separate inlet channels, and subsequently travelled through a serpentine-shaped channel where mixing between the two phases took place. The synthesis process was optimised by varying both liposome formulation and the operating fluidic parameters, including the ratio between inlet flow rates (or flow rate ratio) and the total flow rate. The obtained Lipo/SNPs were characterised for their size and electrostatic charge, using a dynamic light scattering apparatus. Liposome morphology and encapsulation efficiency of SNPs within liposomes were determined by transmission electron microscopy (TEM) imaging. The synthesised negatively charged Lipo/SNP samples were found to have an average size of ∼150 nm (size dispersity < 0.3). The AgNPs encapsulation efficiency was equal to 77.48%, with mostly single SNPs encapsulated in liposomes. By using a multiangle TEM imaging approach, quasi-3D images were obtained, further confirming the encapsulation of nanoparticles within liposomes. Overall, the formulation and production technique developed in the present study has potential to contribute towards mitigating challenges associated with AgNP-mediated drug delivery and diagnostics.

Amyloid Precursor Protein Changes Arrangement in a Membrane and Its Structure Depending on the Cholesterol Content.

One of the hallmarks of Alzheimer's disease (AD) is the accumulation of amyloid beta (Aβ) peptides in the brain. The processing of amyloid precursor protein (APP) into Aβ is dependent on the location of APP in the membrane, membrane lipid composition and, possibly, presence of lipid rafts. In this study, we used atomic force microscopy (AFM) to investigate the interaction between transmembrane fragment APP672-726 (corresponding to Aβ1-55) and its amyloidogenic mutant L723P with membranes combining liquid-ordered and liquid-disordered lipid phases. Our results demonstrated that most of the APP672-726 is located either in the liquid-disordered phase or at the boundary between ordered and disordered phases, and hardly ever in rafts. We did not notice any major changes in the domain structure induced by APP672-726. In membranes without cholesterol APP672-726, and especially its amyloidogenic mutant L723P formed annular structures and clusters rising above the membrane. Presence of cholesterol led to the appearance of concave membrane regions up to 2 nm in depth that were deeper for wild type APP672-726. Thus, membrane cholesterol regulates changes in membrane structure and permeability induced by APP that might be connected with further formation of membrane pores.