Oleic Acid Micelles Research Articles

Tailoring Biotribological Performance of Polytetrafluoroethylene Nanocomposites through Control of Diameters and Aspect Ratios of In Situ Filled Hydroxyapatite Nanowires

Excellent biocompatibility and biotribological performance are necessary for artificial acetabular cups in total hip replacement. Herein, polytetrafluoroethylene (PTFE) nanocomposites are fabricated via an in situ filling of hydroxyapatite nanowires. The resulting nanocomposites are characterized and evaluated by sliding friction against a high‐speed steel ring in the presence of simulated body fluid. Markedly enhanced hydrophobicity, heat resistance, and stiffness are observed for the fabricated nanocomposites in comparison with the matrix PTFE. The ethanol/water ratios for the in situ fabrication of the nanocomposites showed a predominant role in the diameters and aspect ratios of the hydroxyapatite nanowires filled in the nanocomposites. This might be related to the competition between the nucleation and growth of the hydroxyapatite crystals under applied synthetic conditions because the concentration of ethanol can influence the size and morphology of the oleic acid micelles. Furthermore, the diameters and aspect ratios of the nanofiller are found a decisive role in the tribological performance of the resulting PTFE nanocomposites, and those fabricated using a low ethanol/water ratio showed an enhanced diameter and aspect ratio and remarkable improvement in biotribological performance. The fabrication method is believed promising for the design and controllable synthesis of artificial acetabular cups or other artificial tissues.

Effect of alpha-lactalbumin and lactoferrin oleic acid complexes on chromatin structural organization

This work focuses on the study of multimeric alpha-lactalbumin oleic acid and lactoferrin oleic acid complexes. The purpose of the research is to study possible mechanisms involved in their pro-apoptotic activities, as seen in some tumor cell cultures. Complexes featuring oleic acid (OA) with human alpha-lactalbumin (hAl) or with bovine alpha-lactalbumin (bAl), and human lactoferrin (hLf) were investigated using small-angle neutron scattering (SANS). It was shown that while alpha-lactalbumin protein complexes were formed on the surface of polydisperse OA micelles, the lactoferrin complexes comprised a monodisperse system of nanoscale particles. Both hAl and hLf complexes appeared to interact with the chromatin of isolated nuclei affecting chromatin structural organization. The possible roles of these processes in the specific anti-tumor activity of these complexes are discussed.

Controlling Secretion in Artificial Cells with a Membrane AND Gate.

The assembly of channel proteins into vesicle membranes is a useful strategy to control activities of vesicle-based systems. Here, we developed a membrane AND gate that responds to both a fatty acid and a pore-forming channel protein to induce the release of encapsulated cargo. We explored how membrane composition affects the functional assembly of α-hemolysin into phospholipid vesicles as a function of oleic acid content and α-hemolysin concentration. We then showed that we could induce α-hemolysin assembly when we added oleic acid micelles to a specific composition of phospholipid vesicles. Finally, we demonstrated that our membrane AND gate could be coupled to a gene expression system. Our study provides a new method to control the temporal dynamics of vesicle permeability by controlling when the functional assembly of a channel protein into synthetic vesicles occurs. Furthermore, a membrane AND gate that utilizes membrane-associating biomolecules introduces a new way to implement Boolean logic that should complement genetic logic circuits and ultimately enhance the capabilities of artificial cellular systems.

HEWL interacts with dissipated oleic acid micelles, and decreases oleic acid cytotoxicity.

Senile plaques are well-known hallmarks of Alzheimer’s Diseases (AD). However, drugs targeting tangles of the protein tau and plaques of β-amyloid have no significant effect on disease progression, and the studies on the underlying mechanism of AD remain in high demand. Growing evidence supports the protective role of senile plaques in local inflammation driven by S100A9. We herein demonstrate that oleic acid (OA) micelles interact with hen egg white lysozyme (HEWL) and promote its amyloid formation. Consequently, SH-SY5Y cell line and mouse neural stem cells are rescued from OA toxicity by co-aggregation of OA and HEWL. Using atomic force microscopy in combination with fluorescence microscopy, we revealed that HEWL forms round-shaped aggregates in the presence of OA micelles instead of protofibrils of HEWL alone. These HEWL amyloids act as a sink for toxic OA micelles and their co-aggregate form large clumps, suggesting a protective function in amyloid and OA cytotoxicity.

A Fatty Acid Induces the Functional Assembly of a Channel Protein into Phospholipid Vesicles

The release of encapsulated cargo is an important step towards the design of intelligent drug delivery systems or vesicle-based bioreactors. Controlling the integration of pore forming channels into phospholipid vesicle membranes provides a route to initiate content release that could be coupled to gene-expression systems. Here, we present the design of phospholipid vesicles that release cargo upon the temporally controlled assembly of pore-forming channels. Our approach was to design a synthetic vesicle in which membrane composition could be remotely changed to enable the assembly of a pore-forming channel protein, α-hemolysin (αHL), and trigger content release. We first observed that a membrane lacking a sufficient concentration of cholesterol is not compatible with channel assembly and we hypothesized that increasing membrane fluidity, through the addition of oleic acid (OA) micelles could promote channel assembly. Using a dye release assay, we first confirmed that increasing OA content in phospholipid membranes leads to pore assembly. Next, we demonstrated that remote addition of OA micelles to inactive membranes results in fatty acid membrane uptake and channel assembly. We then showed that our system provides a route to control the integration of αHL into vesicle membranes when the channel protein is produced through a cell-free expression system. We remotely added OA micelles to vesicles present in a cell-free expression system where the amount of protein expressed is difficult to control. OA addition led to functional pore assembly and dye release. We ultimately demonstrate a new way to utilize remote changes in membrane composition to control αHL assembly and content release. Our study contributes to the design of vesicle-based technologies and also reveals new insight into the relationship between membrane composition and cholesterol-dependent cytolysin channel assembly.

Transepithelial transfer of phenanthrene, but not of benzo[a]pyrene, is inhibited by fatty acids in the proximal intestine of rainbow trout (Oncorhynchus mykiss)

The inclusion of vegetable oils in aquafeeds introduces contaminating polycyclic aromatic hydrocarbons (PAHs) in salmonids. Since lipophilic PAHs solubilize in micelles composed of lipids, bile salts and fatty acids, dietary lipid composition can alter intestinal transepithelial PAH transfer. We studied the uptake of two PAHs, viz. benzo[a]pyrene (BaP) and phenanthrene (PHE), in rainbow trout (Oncorhynchus mykiss) intestine. We also investigated the effects of two fatty acids, viz. fish oil-derived eicosapentaenoic acid (EPA, 20:5n-3) and vegetable oil-derived oleic acid (18:1n-9) on intestinal uptake. Radiolabeled PAHs were solubilized in micelles composed of tritiated EPA and oleic acid, respectively, and administrated to intestinal segments mounted in Ussing chambers.In the absence of micelles, PHE accumulation was two times higher than BaP in the mucosal and serosal layers of proximal and distal intestine. Administration of PHE in micelles composed of oleic acid resulted in a 50% lower accumulation of PHE in the mucosal layers of the proximal intestine compared to EPA-composed micelles. Accumulation of EPA and oleic acid in the proximal intestinal mucosa correlated negatively with the transepithelial transfer of these fatty acids across the proximal intestinal epithelium. Transepithelial PHE transfer across the proximal intestine was reduced by 30% in co-exposure with EPA-composed micelles compared to 80% with oleic acid micelles. BaP was not transferred across the intestine.We conclude that the lipid composition of an aquafeed is an important determinant of PAH bioavailability. Therefore, lipid composition should be an important consideration in choosing vegetable oils as alternatives for fish oil in aquafeeds.

Influence of olive oil on the bioavailability of carotenoids

Bioavailability is defined as “the fraction of an ingested nutrient that is available for utilization in normal physiological functions or for storage”. Available studies on carotenoids bioavailability are based on the measurement of their levels in serum or plasma. Dietary components were reported to affect the rate of carotenoids absorption. On digestion, carotenoids are incorporated into the lipid phase and then are emulsified into small lipid droplets. The nature and amount of lipids in the diet greatly affect the emulsification, secretion of bile salts, and formation of mixed micelles all of which are currently important subjects to understand the carotenoids bioavailability. Specific lipids, vegetable oils and their fatty acid moiety have been shown to affect the mixed micelles formation that positively influences the absorption of carotenoids. Gavages and dietary studies revealed that oleic acid micelles and olive oil (oleic acid, C18:1) enhance the intestinal accessibility of carotenoids more than linoleic acid micelles or vegetables oils rich in polyunsaturated fatty acids (PUFA). The chemistry of fats or oils which may act differently at various stages of absorption and metabolism of carotenoids is discussed. This review shows that dietary unsaturated fat appears to be a suitable carrier for carotenoids when oxidative stress is a critical issue in nutrition‐related degenerative disorders.

Weak Acid–Base Interaction Induced Assembly for the Synthesis of Diverse Hollow Nanospheres

We have established a novel and generalizable hydrothermal synthesis for diverse hollow nanospheres, which cover polymer, carbon, graphitic carbon, and metal-doped carbon hollow nanospheres. The synthesis principle is based on the weak acid–base interaction (−COO–/NH4+/–COO–) induced assembly. That is, the ammonium cations from the reactant ammonia act as a trigger for the assembly of COO– group-containing polymer around surfactant oleic acid micelles through the weak interaction between carboxylate anion and ammonium ion. Consequently, hollow polymer nanospheres (HPSs) with diameters ranging from 100 to 200 nm and hollow core sizes ranging from 30 to 80 nm can be synthesized. It was determined that approximately 61% of the added amount of NH3 participates is retained in the HPS product. Taking these HPSs as the precursor, hollow carbon nanospheres (HCSs) with tunable surface areas can be obtained by varying the preparation conditions. More importantly, owing to the presence of the COO– functional groups, a wide range of metal cations (e.g., Fe3+ and Ag+) can be successfully introduced into these HPSs, so that they can then be converted to hollow graphitized nanospheres and Ag-doped catalytically active HCSs.

Trans Fatty Acids in Membranes: The Free Radical Path

The double bond geometry of most of the naturally occurring unsaturated fatty acid residues is cis. Due to the relevance of fatty acids as structural components of cell membranes and as biologically active molecules, the change of the cis geometry means a change of the associated functions and activities. The finding that the cis to trans isomerization is effective in phospholipids by the intervention of radical species led to the discovery that there can indeed occur an endogenous formation of trans fatty acids, whose significance in biological systems started to be addressed with in vitro and in vivo studies. Studies of liposome models simulating the formation of isomerizing species and evaluating their ability to interact with the hydrophobic part of the membrane bilayer has contributed to the gain in knowledge of the fundamental features of the lipid isomerization in membranes. Further work is in progress for the identification of the real culprits of the in vivo lipid isomerization, and recent results are shown on oleic acid micelles, where *NO2 radicals are not able to induce double bond isomerization in comparison with amphiphilic thiol, such as 2-mercaptoethanol. H2S and sulfur-containing amino acid residues are two of the possible species involved in this process at a biological level. An update of the scenario of the geometrical isomerization in membranes by free radicals is provided, together with applications and perspectives in life sciences.

Spindly cobalt ferrite nanocrystals: preparation, characterization and magneticproperties

In this paper we describe the preparation of homogeneously needle-shaped cobalt ferrite(CoFe2O4)nanocrystals on a large scale through the smooth decomposition of urea and the resulting co-precipitationof Co2+ and Fe3+ in oleic acid micelles. Furthermore, we found that other ferritenanocrystals with a needle-like shape, such as zinc ferrite(ZnFe2O4) and nickelferrite (NiFe2O4), can be prepared by the same process. Needle-shapedCoFe2O4 nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellentstability and the formed colloid does not produce any precipitations after twomonths, which is of prime importance if these materials are applied in magneticfluids. X-ray diffraction (XRD) measurements were used to characterize the phaseand component of the co-precipitation products, and demonstrate that they arespinel ferrite with a cubic symmetry. Transmission electron microscopy (TEM)observation showed that all the nanocrystals present a needle-like shape with a 22 nmshort axis and an aspect ratio of around 6. Varying the concentration of oleic aciddid not bring about any obvious influence on the size distribution and shapes ofCoFe2O4. The magnetic properties of the needle-shapedCoFe2O4 nanocrystals were evaluated by using a vibrating sample magnetometer (VSM), electronparamagnetic resonance (EPR), and a Mössbauer spectrometer, and the results all demonstrated thatCoFe2O4 nanocrystals were superparamagnetic at room temperature.

Fatty acid chlorohydrins and bromohydrins are cytotoxic to human endothelial cells

Reaction of unsaturated lipids with the hypohalous acids (hypochlorous acid and hypobromous acid) results in the addition of the halide (X) across double bonds to form halohydrins (-CH2CH(OH)CH(X)CH2-). These modified lipids could be potentially destabilising to cell membranes due to their increased polarity. We have investigated the effect of pre-formed halohydrins on human umbilical vein endothelial cells (HUVEC) by incubating cultured cells with oleic acid micelles containing chlorohydrins or bromohydrins. Cell detachment and necrotic death were observed with increasing doses of halohydrins, whereas the cells were unaffected by equivalent doses of oleic acid. Bromohydrins caused more lysis than did chlorohydrins at equivalent doses. Complete lysis was seen with 200 muM fatty acidchlorohydrin micelles and with 50 muM fatty acidbromohydrin micelles. Chlorohydrin uptake was much less than the oleic acid control whereas bromohydrins were incorporated into the endothelial cells similarly to oleic acid. This difference or the bulkier nature of the bromohydrins could account for their increased toxicity. This study has demonstrated the potential toxicity of the halohydrins, and implications for their formation in inflammation are discussed.