This work presents a simple methodology for coating small unilamellar liposomes bearing different degrees of positive charge with polyelectrolyte multilayers using the sequential layer-by-layer ...deposition method. The liposomes were made of mixtures of 1,2-dioleyl-sn-glycero-3-phosphocoline and dimethyl dioctadecyl ammonium bromide (DODAB) and coated by alternated layers of the sodium salt of poly(4-styrenesulfonate) (PSS) and poly(allylamine) (PAH) as polyanions and polycations, respectively. The results show that the zeta potential of the liposomes was not very sensitive to the mole fraction of DODAB in the membrane, X D, in the range 0.3 ≤ X D ≤ 0.8. We were able to coat the liposomes with up to four polymer bilayers. The growth of the capsule size was followed by dynamic light scattering, and in some cases, by cryo-transmission electron microscopy, with good agreement between both techniques. The thickness of the layers, measured from the hydrodynamic radius of the coated liposome, depends on the polyelectrolyte used, so that the PSS layers adopt a much more packaged conformation than the PAH layers. An interesting finding is that the PSS amount needed to reach the isoelectric point of the capsules increases linearly with the charge density of the bare liposomes, whereas the amount of PAH does not depend on it. As expected, the preparation of the multilayers has to be done in such a way that when the system is close to the isoelectric point, the capsules do not aggregate. For this, we dropped the polyelectrolyte solution quickly, stirred it fast, and used dilute liposome suspensions. The method is very flexible and not limited to liposomes or polyelectrolyte multilayers; also, coatings containing charged nanoparticles can be easily made. Once the liposomes have been coated, lipids can be easily eliminated, giving rise to polyelectrolyte nanocapsules (polyelectrosomes) with potential applications as drug delivery platforms.
Most of the currently used products for repairing and conditioning hair rely on the deposition of complex formulations, based on mixtures involving macromolecules and surfactants, onto the surface of ...hair fibers. This leads to the partial covering of the damaged areas appearing in the outermost region of capillary fibers, which enables the decrease of the friction between fibers, improving their manageability and hydration. The optimization of shampoo and conditioner formulations necessitates a careful examination of the different physicochemical parameters related to the conditioning mechanism, e.g., the thickness of the deposits, its water content, topography or frictional properties. This review discusses different physicochemical aspects which impact the understanding of the most fundamental bases of the conditioning process.
Carbonaceous particles are accounted among the most common environmental pollutants. This makes necessary a careful examination of their potential impact on the physico-chemical properties of ...different biological films, e.g. tear film, skin, or lung surfactant. This work analyzes the interaction of three different types of carbonaceous particles with Langmuir monolayers of 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC) spread at the water/vapor interface. This type of studies can be exploited as preliminary in vitro tests for evaluating the potential risks and hazards of this type of pollutants for human health, which requires to study the effect of the particles on the ability of lipid layers for reducing the surface tension under static and dynamics conditions. The obtained results have shown that the insertion of particles into lipid films leads to the emergence of excluded area-like effects which modify the interfacial cohesion and packing. This hinders partially the ability of the lipid films for reducing the surface tension, which may present important adverse effects for the normal physiological performance of lipid membranes, and in particular for the performance of lung surfactant layers. Furthermore, the analysis of the response of lipid layers including carbonaceous particles against mechanical stresses also evidenced that particle incorporation worsens the mechanical performance of lipid layers, which may alter both their functional and structural roles.
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•Incorporation of carbonaceous particles into DPPC films modifies the lateral packing of lipids.•Modification of lateral packing alter the equilibrium and dynamic behavior of the interfacial layers.•Particles induce a strong weakening of the lateral interactions at the interface.•Partial inhibition of the ability of lipid layer for reducing surface tension.
Silica nanoparticles (SiNP) can be incorporated in phospholipid layers to form hybrid organic–inorganic bidimensional mesostructures. Controlling the dynamics in these mesostructures paves the way to ...high-performance drug-delivery systems. Depending on the different hydrophobicity/hydrophilicity of SiNP, recent X-ray reflectivity experiments have demonstrated opposite structural effects. While these are reasonably well understood, less is known about the effects on the dynamics, which in turn determine molecular diffusivity and the possibility of drug release. In this work we characterize the dynamics of a mixed Langmuir layer made of phospholipid and hydrophobic SiNP. We combine X-ray photon correlation spectroscopy and epifluorescence discrete Fourier microscopy to cover more than 2 decades of Q-range (0.3–80 μm–1). We obtain evidence for the onset of an arrested state characterized by intermittent stress-relaxation rearrangement events, corresponding to a gel dominated by attractive interactions. We compare this with our previous results from phospholipid/hydrophilic SiNP films, which show an arrested glassy phase of repulsive disks.
The cosmetic industry has an undeniable need to design and develop new ecosustainable products to respond to the demands of consumers and international regulations. This requires substituting some ...traditional ingredients derived from petrochemical sources with new ones with more ecofriendly profiles. However, this transition towards the use of green ingredients in the cosmetic industry cannot compromise the effectiveness of the obtained products. Emerging ingredients in this new direction of the cosmetic industry are chitosan and its derivatives, which combine many interesting physicochemical and biological properties for the fabrication of cosmetic products. Thus, the use of chitosan opens a promising future path to the design of cosmetic formulations. In particular, chitosan’s ability for interacting electrostatically with negatively charged substrates (e.g., skin or damaged hair), resulting in the formation of polymeric films which contribute to the conditioning and moisturizing of cosmetic substrates, makes this polymer an excellent candidate for the design of skin and hair care formulations. This review tries to provide an updated perspective on the potential interest of chitosan and its derivatives as ingredients of cosmetics for skin and hair care.
The construction of nanostructured materials for their application in electrochemical processes, e.g., energy storage and conversion, or sensing, has undergone a spectacular development over the last ...decades as a consequence of their unique properties in comparison to those of their bulk counterparts, e.g., large surface area and facilitated charge/mass transport pathways. This has driven strong research on the optimization of nanostructured materials for the fabrication of electrochemical devices, which demands techniques allowing the assembly of hybrid materials with well-controlled structures and properties. The Layer-by-Layer (LbL) method is well suited for fulfilling the requirements associated with the fabrication of devices for electrochemical applications, enabling the fabrication of nanomaterials with tunable properties that can be exploited as candidates for their application in fuel cells, batteries, electrochromic devices, solar cells, and sensors. This review provides an updated discussion of some of the most recent advances on the application of the LbL method for the fabrication of nanomaterials that can be exploited in the design of novel electrochemical devices.
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•Eugenol in water nanoemulsions can be stabilized by poloxamer 407.•Nanoemulsions enable the solubilization of the synthetic insecticide pyriproxyfen.•Good encapsulation efficiency of ...the nanoemulsions.•Nanoemulsions present a good long-term stability.
The encapsulation of a synthetic insecticide, pyriproxyfen, has been carried out using eugenol in water nanoemulsions, including different weight fractions of oil phase (eugenol), and stabilized by a triblock amphiphilic copolymer, poloxamer 407. Dynamic Light Scattering (DLS) experiments have evidenced the formation of polydisperse nanoemulsions, in both nanoemulsions free of the insecticide and those containing it. These nanoemulsion present a good long-term stability, and only a slight sedimentation of the bigger droplets was found after several months of storage (the aging during 24 months of the nanoemulsions was evaluated). This long-term chemical and physical stability is important for the potential application of these systems in insect pest control, which may also take advantage of the high solubilization efficiency of piryproxyfen evidenced by the nanoemulsions. Therefore, this study combined with an additional evaluation of the efficiency of these formulations, may open many possibilities for the preparation of ready-to-use formulations against different insect pests.
Aims
The present study evaluated the effect of four functional diets and a reference diet on the survival and intestinal bacterial community of shrimp Penaeus vannamei infected with acute ...hepatopancreatic necrosis disease (AHPND).
Methods and Results
After 42 days of feeding trail, shrimp were inoculated with a Vibrio parahaemolyticus (CIB‐0018‐3) carrying the plasmid encoding for the PirAB toxins responsible for AHPND. After 120 h postinfection (hpi), shrimp fed with a diet containing 2% of a mix with Curcuma longa and Lepidium meyenii (TuMa) and a diet containing 0.2% of vitamin C (VitC) showed a significantly higher survival (85%) compared to the remaining treatments (50%–55%) (p < 0.05). Infected shrimp fed with TuMa diet, showed a significant reduction of Vibrionales, and VitC diet promoted an increase of Alteromonadales.
Conclusions
Our findings suggest that the TuMa diet conferred protection against AHPND and could be attributed to a combined effect of antibacterial properties against Vibrionales, and promoting a desirable bacterial community in the shrimp intestine, while the VitC diet protection could be attributed to their antioxidant capacity and in a lower proportion to a bacterial modulation in shrimp gut.
Significance and Impact of the Study
Acute hepatopancreatic necrosis disease is a devastating disease that significantly affects aquaculture production of shrimps. Therefore, the use of functional diets that promote resistance to AHPND represents a valuable tool to reduce the mortality of farmed shrimp.
The use of polymer and polymer - surfactant mixtures for designing and developing textile and personal care cosmetic formulations is associated with various physico-chemical aspects, e.g. detergency ...and conditioning in the case of hair or wool, that determine their correct performances in preserving and improving the appearance and properties of the surface where they are applied. In this work, special attention is paid to the systems combining polycations and negatively charged surfactants. The paper introduces the hair surface and presents a comprehensive review of the adsorption properties of these systems at solid-water interfaces mimicking the negative charge and surface energy of hair. These model surfaces include mixtures of thiols that confer various charge densities to the surface. The kinetics and factors that govern the adsorption are discussed from the angle of those used in shampoos and conditioners developed by the cosmetic industry. Finally, systems able to adsorb onto negatively charged surfaces regardless of the anionic character are presented, opening new ways of depositing conditioning polymers onto keratin substrates such as hair.
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•Adsorption of polymer and polymer+surfactant complexes is important in cosmetics.•Polyelectrolyte+surfactant systems are the main components of cosmetic formulations.•Good substantivity is critical in the use of polyelectrolytes and surfactants in cosmetics.•Adsorption depends on the interplay of electrostatic and hydrophobic interactions.•Model systems allow understanding the adsorption of real formulations.
Effect of silica nanoparticles on DPPC+Cholestrol compression isotherm. Display omitted
► The interaction between lipid monolayers and nanoparticles was studied. ► Analysis by Langmuir trough ...technique and Brewster Angle Microscopy. ► Silica nanoparticles penetrate Langmuir monolayers of Cholesterol and DPPC. ► Nanoparticles penetration alters the interfacial properties of lipid monolayers. ► The results point out strong physiological relevance matters.
Langmuir monolayers of Cholesterol (Chol) and a mixture of Chol with 1,2-Dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), at a ratio of 17:83 in weight, spread on pure water and on silica nanoparticle dispersions, have been investigated measuring the compression isotherms as well as the surface pressure response to harmonic area variation of the monolayer. Aim of this study was to evaluate the effects of the interaction of silica nanoparticles with Chol and the conditions for the incorporation in the monolayer. In previous works on different kind of lipid monolayers, it has been shown that hydrophilic silica nanoparticles dispersed in the sub-phase may transfer into the monolayer, driven by the interaction with the lipid molecules that make them partially hydrophobic. The results here obtained indicate that also for Chol and Chol–DPPC mixtures the presence of silica nanoparticles may have important effects on the phase behaviour and structural properties of the monolayer. As confirmed by complementary structural characterisations, BAM, AFM and ellipsometry, the principal effect of the nanoparticle incorporation is the disruption of the monolayer packing, owing to the alteration of the cohesive interactions of lipid components.
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