Cationic–anionic vesicle templating from fluorocarbon/fluorocarbon and hydrocarbon/fluorocarbon surfactants

The Fabrication of Oleophobic Coating and Its Application in Particulates Filtration

The stir-frying process in Chinese cooking has produced serious emissions of oily particles, which are an important source of urban air pollution. In particular, the complex composition of fine particulate may pose a threat to human respiratory and immune systems. However, current filtration methods for oily particulate fumes have low filtration efficiency, high resistance, and high equipment costs. In polypropylene (PP) electret filters, efficiency rapidly decreases and pressure drop (wind resistance) sharply increases after the adsorption of oily particles, due to the oleophilic properties of the PP fibre. We addressed this issue of filter performance degradation by fabricating a sodium perfluorooctanoate (SPFO) oleophobic coating on polyvinylidene fluoride (PVDF) fibre membranes for oily particle filtration. The SPFO coating showed a promising oleophobic effect even at low concentrations, which suggests it has oleophobic properties for different oil types and can be modified for different substrates. This fabricated oleophobic coating is thermostable and the oleophobic effect is unaffected by temperatures from 0 to 100 °C. By modifying the SPFO coating on the PVDF membrane, a high filtration efficiency (89.43%) and low wind resistance (69 Pa) was achieved without oil adhesion, so the proposed coating can be applied in the filtration and purification of oily fine particles and offers a potential strategy for preventing atmospheric oil pollution.

Formation of polyhedral vesicle gels from catanionic mixtures of hydrogenated and perfluorinated surfactants: effect of fluoro-carbon alkyl chain lengths

The effects of alkyl chain length of anionic fluorinated fatty acid surfactants, CnF2n+1COOH (n = 7-11), mixed with one cationic hydrocarbon surfactant, tetradecyltrimethylammonium hydroxide (TTAOH), on the formation of polyhedral vesicle gels were investigated in aqueous solutions. On the basis of phase behavior mapping, C8F17COOH, C9F19COOH, C10F21COOH and C11F23COOH except C7F15COOH all formed polyhedral vesicle gels when they were mixed with TTAOH under certain mixed ratios, which was demonstrated by freeze-fracture transmission electron microscopy (FF-TEM) measurements. Meanwhile, the following observation was not observed: the longer the fluorinated alkyl chain, the more effective the formation of gels by fluorinated fatty acids. The formation of the faceted vesicle gels was determined both by the rigidity of the fluorinated alkyl chain and the co-crystallization of fluorocarbon chains and hydrocarbon chains, as revealed by the results of differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and 19F NMR measurements. Furthermore, the polyhedral vesicle gels showed high viscoelasticity, which increased clearly with increasing fluorinated alkyl chain length, indicating that the viscoelastic property of the polyhedral vesicle gel was a result of the crystalline state of the polyhedral vesicle bilayers at room temperature. As far as we know, such polyhedral vesicle gels formed from perfluorinated and hydrocarbon surfactant mixtures have been rarely reported. Our study can be a great advancement in fundamental research of surfactant vesicle gels.

Solid lipid nanoparticles of clotrimazole silver complex: An efficient nano antibacterial against Staphylococcus aureus and MRSA

New and effective strategies to transform current antimicrobials are required to address the increasing issue of microbial resistance and declining introduction of new antibiotic drugs. In this context, metal complexes of known drugs and nano delivery systems for antibiotics are proving to be promising strategies. The aim of the study was therefore to synthesize a silver complex of clotrimazole and formulate it into a nano delivery system for enhanced and sustained antibacterial activity against susceptible and resistant Staphylococcus aureus. A silver complex of clotrimazole was synthesized, characterized and further encapsulated into solid lipid nanoparticles to evaluate its antibacterial activity against S. aureus and methicillin-resistant S. aureus (MRSA). An in vitro cytotoxicity study was performed on HepG2 cell lines to assess the overall biosafety of the synthesized clotrimazole silver complex to mammalian cells, and was found to be non-toxic to mammalian cells (cell viability >80%). The minimum inhibitory concentrations (MIC) of clotrimazole and clotrimazole-silver were 31.25 and 9.76 μg/mL against S. aureus, and 31.25 and 15.62 against MRSA, respectively. Clotrimazole SLNs exhibited MIC values of 104 and 208 μg/mL against both MSSA and MRSA at the end of 18 and 36 h, respectively, but thereafter completely lost its antibacterial activity. Clotrimazole-silver SLNs had an MIC value of 52 μg/mL up to 54 h, after which the MIC value was 104 μg/mL against both strains at the end of 72 h. Thus, clotrimazole-silver SLNs was found to be an efficient nanoantibiotic.

Novel catanionic surfactant vesicle vaccines protect against Francisella tularensis LVS and confer significant partial protection against F. tularensis Schu S4 strain

Francisella tularensis is a Gram-negative immune-evasive coccobacillus that causes tularemia in humans and animals. A safe and efficacious vaccine that is protective against multiple F. tularensis strains has yet to be developed. In this study, we tested a novel vaccine approach using artificial pathogens, synthetic nanoparticles made from catanionic surfactant vesicles that are functionalized by the incorporation of either F. tularensis type B live vaccine strain (F. tularensis LVS [LVS-V]) or F. tularensis type A Schu S4 strain (F. tularensis Schu S4 [Schu S4-V]) components. The immunization of C57BL/6 mice with "bare" vesicles, which did not express F. tularensis components, partially protected against F. tularensis LVS, presumably through activation of the innate immune response, and yet it failed to protect against the F. tularensis Schu S4 strain. In contrast, immunization with LVS-V fully protected mice against intraperitoneal (i.p.) F. tularensis LVS challenge, while immunization of mice with either LVS-V or Schu S4-V partially protected C57BL/6 mice against an intranasal (i.n.) F. tularensis Schu S4 challenge and significantly increased the mean time to death for nonsurvivors, particularly following the i.n. and heterologous (i.e., i.p./i.n.) routes of immunization. LVS-V immunization, but not immunization with empty vesicles, elicited high levels of IgG against nonlipopolysaccharide (non-LPS) epitopes that were increased after F. tularensis LVS challenge and significantly increased early cytokine production. Antisera from LVS-V-immunized mice conferred passive protection against challenge with F. tularensis LVS. Together, these data indicate that functionalized catanionic surfactant vesicles represent an important and novel tool for the development of a safe and effective F. tularensis subunit vaccine and may be applicable for use with other pathogens.

Lysine-based surfactants in nanovesicle formulations: the role of cationic charge position and hydrophobicity in in vitro cytotoxicity and intracellular delivery

Understanding nanomaterial interactions within cells is of increasing importance for assessing their toxicity and cellular transport. Here, the authors developed nanovesicles containing bioactive cationic lysine-based amphiphiles and assessed whether these cationic compounds increase the likelihood of intracellular delivery and modulate toxicity. Different cytotoxic responses were found among the formulations, depending on surfactant, cell line and endpoint assayed. The induction of mitochondrial dysfunction, oxidative stress and apoptosis were the general mechanisms underlying cytotoxicity. Fluorescence microscopy analysis demonstrated that nanovesicles were internalised by HeLa cells and evidenced that their ability to release endocytosed materials into cell cytoplasm depends on the structural parameters of amphiphiles. The cationic charge position and hydrophobicity of surfactants determine the nanovesicle interactions within the cell and, thus, the resulting toxicity and intracellular behaviour after cell uptake of the nanomaterial. The insights into some toxicity mechanisms of these new nanomaterials contribute in reducing the uncertainty surrounding their potential health hazards.

Phase behavior and self-assembly aggregation of hydrocarbon and fluorocarbon surfactant mixtures in aqueous solution

Similar to hydrogenated surfactant mixtures, the ones of hydrocarbon and fluorocarbon surfactants can also self-assemble into various aggregates, including mixed micelles and vesicles, however, completely different phase behavior and self-assembly of CH/CF surfactant mixtures in solution can be observed and exhibit novel features because of the repellence between the two hydrophobic chains. These systems of hydrocarbon and fluorocarbon surfactant mixtures can provide important considerations for both theoretical and applied interest. Several advantaged techniques, including small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), (19)F- and (1)H-NMR, cryo-TEM, and Freeze-fracture TEM (FF-TEM) have been widely employed to characterize these mixture systems. In this review, the aggregation behavior, self-assembly aggregation, and interaction of hydrocarbon and fluorocarbon surfactant mixtures in solution are described and focused three aspects, (i) immiscibility and nonideal mixing in hydrocarbon and fluorocarbon surfactant mixed micelles systems; (ii) spontaneous vesicles of hydrocarbon and fluorocarbon surfactant mixtures in aqueous solution; and (iii) self-assembled aggregates of hybrid fluorocarbon/hydrocarbon surfactants in aqueous solutions.

Characterization of fluorinated catansomes: a promising vector in drug-delivery

Catansomes, which are vesicles prepared from mixtures of oppositely charged surfactants, have been suggested as effective alternatives to phospholipid vesicles, i.e., liposomes, in applications such as drug-delivery. This is mainly due to their enhanced chemical and physical stability as well as to their relatively easy preparation, which is an advantage for large-scale productions. In this study we have investigated catansomes prepared from a perfluorinated anionic surfactant (sodium perfluorooctanoate) premixed with a hydrogenated cationic surfactant (dodecyltrimethylammonium bromide or 1-dodecylpyridinium chloride). The aim was to gain insights into the physicochemical properties of these systems, such as size, stability, surface charge, and membrane morphology, which are essential for their use in drug-delivery applications. The catansomes were mostly unilamellar and 100-200 nm in size, and were stable for more than five months at room temperature. After loading the catansomes with the fluorescent marker calcein, they were found to exhibit an appreciable encapsulation efficiency and a low calcein leakage over time. The addition of fatty acids to calcein-loaded catansomes considerably promoted the release of calcein, and the rate and efficiency of calcein release were found to be proportional to the fatty acid concentration and chain length. Our results prove the feasibility of utilizing catansomes as drug-delivery vehicles as well as provide a means to efficiently release the encapsulated load.

Synthesis and self-assembly of an amino-functionalized hybrid hydrocarbon/fluorocarbon double-chain phospholipid

In this article, we designed and synthesized an amino-functionalized hybrid hydrocarbon/fluorocarbon double-chain phospholipid (ACFPC) containing one chain with the hydrophobic fluorocarbon chain and terminal amino, amide, and ether linkages and one chain with the hydrocarbon chain. The novel reactive phospholipid was fully characterized with Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR), and mass spectrometry (MS). Then the self-assembly behaviors of the hybrid double-chain phospholipid in aqueous and acidic media were investigated with transmission electron microscopy (TEM), the critical micelle concentration (cmc), dynamic light scattering (DLS), and the hydrocarbon double-chain phospholipid (ACCPC) for comparison. Moreover, their self-assembled structures in aqueous and acidic media were simulated using the dissipative particle dynamics (DPD) method. These results suggest that the fluorocarbon/hydrocarbon hybrid-chain phospholipid can self-assemble into a more stable microstructure compared to the double hydrocarbon chain phospholipid, which will have the potential ability to self-assemble into a more stable minicking biomembrane structure onto material surfaces to inhibit protein adsorption under complicated physiological conditions.

Negative staining and cryo-negative staining of macromolecules and viruses for TEM

In this review we cover the technical background to negative staining of biomolecules and viruses, and then expand upon the different possibilities and limitations. Topics range from conventional air-dry negative staining of samples adsorbed to carbon support films, the variant termed the "negative staining-carbon film" technique and negative staining of samples spread across the holes of holey-carbon support films, to a consideration of dynamic/time-dependent negative staining. For each of these approaches examples of attainable data are given. The cryo-negative staining technique for the specimen preparation of frozen-hydrated/vitrified samples is also presented. A detailed protocol to successfully achieve cryo-negative staining with ammonium molybdate is given, as well as examples of data, which support the claim that cryo-negative staining provides a useful approach for the high-resolution study of macromolecular and viral structure.