Wormlike micelles of CTAB with phenols and with the corresponding phenolate derivatives - When hydrophobicity and charge drive the coacervation.

HYPOTHESIS: Hydrophobicity and the presence or absence of charge in phenol derivatives are relevant on the rheology and phase behavior when they are assembled with a cationic surfactant, forming wormlike micelles. The incorporation of phenols with a greater number of rings into the micellar palisade is entropically favored, but a solubilization limit or coacervation are two paths followed by the solutions, depending on the electrical nature of the aromatic co-solutes. EXPERIMENTS: The investigations were carried out with systems formed by a fixed concentration of hexadecyltrimethylammonium bromide (CTAB) and increasing concentrations of neutral phenols (1-naphthol, 2-naphthol, 2,3-dihydroxynaphthalene and R and S-binol) and with their corresponding phenolate derivatives. The monophasic limits of the systems were established, as well as their linear and non-linear rheology. The structural investigation of the coacervates formed with the phenolates were done using SAXS and Cryo-TEM. FINDINGS: The zero-shear viscosity of the solutions reaches maxima values close to the solubility limit of the aromatics, which depends on the numbers of rings and hydroxyl groups (position and number). However, when the correspondent ionized phenols were investigated, beyond the maxima values for the zero-shear viscosity, liquid-liquid biphasic systems are formed, in which the upper phase contains a coacervate, associated with branched wormlike micelles. However, when the ratio between phenolate and CTAB is around 3:1 the coacervate evolves to a lamellar structure.

Nanoparticle-Protein Interaction: Demystifying the Correlation between Protein Corona and Aggregation Phenomena.

Protein corona formation and nanoparticles' aggregation have been heavily discussed over the past years since the lack of fine-mapping of these two combined effects has hindered the targeted delivery evolution and the personalized nanomedicine development. We present a multitechnique approach that combines dynamic light and small-angle X-ray scattering techniques with cryotransmission electron microscopy in a given fashion that efficiently distinguishes protein corona from aggregates formation. This methodology was tested using ∼25 nm model silica nanoparticles incubated with either model proteins or biologically relevant proteomes (such as fetal bovine serum and human plasma) in low and high ionic strength buffers to precisely tune particle-to-protein interactions. In this work, we were able to differentiate protein corona, small aggregates formation, and massive aggregation, as well as obtain fractal information on the aggregates reliably and straightforwardly. The strategy presented here can be expanded to other particle-to-protein mixtures and might be employed as a quality control platform for samples that undergo biological tests.

Cubic-to-inverted micellar and the cubic-to-hexagonal-to-micellar transitions on phytantriol-based cubosomes induced by solvents.

Cubosomes are nanoparticles composed of a specific combination of some types of amphiphilic molecules like lipids, such as phytantriol (PHY), and a nonionic polymer, like poloxamer (F127). Cubosomes have a high hydrophobic volume (> 50%) and are good candidates for drug delivery systems. Due to their unique structure, these nanoparticles possess the ability to incorporate highly hydrophobic drugs. A challenge for the encapsulation of hydrophobic molecules is the use of organic solvents in the sample preparation process. In this study, we investigated the structural influence of four different solvents (acetone, ethanol, chloroform, and octane), by means of small-angle X-ray scattering and cryogenic electron microscopy techniques. In the presence of a high amount of acetone and ethanol (1:5 solvent:PHY volumetric ratio), for instance, a cubic-to-micellar phase transition was observed due to the high presence of these two solvents. Chloroform and octane have different effects over PHY-based cubosomes as compared to acetone and ethanol, both of them induced a cubic-to-inverse hexagonal phase transition. Those effects are attributed to the insertion of the solvent in the hydrophobic region of the cubosomes, increasing its volume and inducing such transition. Moreover, a second phase transition from reversed hexagonal-to-inverted micellar was observed for chloroform and octane. The data also suggest that after 24 h of solvent/cubosome incubation, some structural features of cubosomes change as compared to the freshly prepared samples. This study could shed light on drug delivery systems using PHY-based cubosomes to choose the appropriate solvent in order to load the drug into the cubosome.Graphical abstract.

S-nitrosothiol-terminated Pluronic F127: Influence of microstructure on nitric oxide release.

HYPOTHESIS: Nitric oxide (NO)-releasing Pluronic F127 hydrogels (F127) containing dissolved S-nitrosothiols or pendant N-diazeniumdiolate (NONOate) groups have been described. The NO charging of these hydrogels is usually limited by their low stability or disruption of the micellar packing. S-nitrosothiol-terminated F127 may emerge as a new strategy for allowing NO delivery at different rates in biomedical applications. EXPERIMENTS: Terminal hydroxyl groups of F127 were esterified and reduced to produce F127-mercaptopropionate (HS-F127-SH), which was subsequently S-nitrosated to generate S-nitrosothiol-terminated F127 (ONS-F127-SNO). Micro-differential scanning calorimetry, 1H NMR spin-spin relaxation (T2), temperature-dependent small-angle X-ray scattering, and cryo-transmission electron microscopy, were used to determine the micellar packing structure, while real-time chemiluminescence NO detection and UV-Vis spectrophotometry were used to evaluate the kinetics of NO release. FINDINGS: HS-F127-SH micellization and gelation processes were analogous to native F127, however, with a decreased short-range ordering of the micelles. ONS-F127-SNO hydrogels released NO thorough a preferentially intramicellar SNO dimerization reaction. Increasing ONS-F127-SNO concentration reduces the rate of SNO dimerization and increases the overall rate of NO release to the gas phase, opening up new possibilities for tailoring NO delivery from F127-based hydrogels.

Characterization of phospholipid vesicles containing lauric acid: physicochemical basis for process and product development.

Lauric acid (LAH) strongly inhibits the growth of acne-causing bacteria. LAH is essentially water-insoluble and the solubility of laurate (LA) salts are medium and temperature dependent. Hence, LAH/LA preparations are difficult to formulate. Here we fully characterized phospholipid vesicles containing up to 50 mol% LAH. Vesicles of dipalmitoylphosphatidylcholine (DPPC) containing LAH, at pHs 7.4 and 5.0, were characterized measuring size, charge, bilayer phase transition temperature (Tm) and permeability of water-soluble probes. Small angle X-ray scattering and cryotransmission electron microscopy showed multilamellar vesicles at low LAH %. Increasing LAH % had a negligible effect on particle size. An internal aqueous compartment in all vesicle's preparations, even at equimolar DPPC: LAH fractions, was demonstrated using water-soluble probes. At pH 5.0, the interaction between DPPC and LAH increased the Tm and phase transition cooperativity showing a single lipid phase formed by hydrogen-bonded DPPC: LAH complexes. At pH 7.4, vesicles containing 50 mol% LAH exhibited distinct phases, ascribed to complex formation between LAH and LA or LAH and DPPC. LAH incorporated in the vesicles minimally permeated a skin preparation at both pHs, indicating that the primary sites of LAH solubilization were the skin layers. These results provide the foundations for developing processes and products containing DPPC: LAH.

Interaction of graphene oxide with cell culture medium: Evaluating the fetal bovine serum protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions.

The interaction of single-layer graphene oxide (SLGO) and multi-layered graphene oxide (MLGO) with a cell culture medium (i.e. DMEM) was studied by evaluating fetal bovine serum (FBS) protein corona formation towards in vitro nanotoxicity assessment and nanobiointeractions. SLGO and MLGO exhibited different colloidal behavior in the culture medium, which was visualized by cryogenic transmission electron microscopy in situ analysis. Exploring proteomics and bioinformatics tools, 394 and 290 proteins were identified on the SLGO and MLGO hard corona compositions, respectively. From this amount, 115 proteins were exclusively detected on the SLGO and merely 11 on MLGO. SLGO enriched FBS proteins involved in metabolic processes and signal transduction, while MLGO enriched proteins involved in cellular development/structure, and lipid transport/metabolic processes. Such a distinct corona profile is due to differences on surface chemistry, aggregation behavior and the surface area of GO materials. Hydrophilic interactions were found to play a greater role in protein adsorption by MLGO than SLGO. Our results point out implications for in vitro studies of graphene oxide materials concerning the effective dose delivered to cells and corona bioactivity. Finally, we demonstrated the importance of integrating conventional and modern techniques thoroughly to understand the GO-FBS complexes towards more precise, reliable and advanced in vitro nanotoxicity assessment.

A sumatriptan coarse-grained model to explore different environments: interplay with experimental techniques.

In this work, we developed a coarse-grained model of sumatriptan suitable for extensive molecular dynamics simulations. First, we confirmed the interfacial distribution of this drug in bilayers through cryogenic transmission electron microscopy and small-angle X-ray scattering techniques, as was predicted by our previous atomistic simulations. Based on these simulations, we developed a coarse-grained model for sumatriptan able to reproduce its overall molecular behavior, captured by atomistic simulations and experiments. We then tested the sumatriptan model in a micellar environment along with experimental characterization of sumatriptan-loaded micelles. The simulation results showed good agreement with photon correlation spectroscopy and electrophoretic mobility experiments performed in this work. The particle size of the obtained micelles was comparable with the simulated ones; meanwhile, zeta-potential results suggest adsorption of the drug on the micellar surface. This model is a step forward in the search for a suitable drug-delivery system for sumatriptan.

Impact of preparation method and variables on the internal structure, morphology, and presence of liposomes in phytantriol-Pluronic(®) F127 cubosomes.

The formation of significant proportions of liposomes during the preparation of dispersed cubic phase particles presents a problem in trying to understanding cubosome behavior with a view to use in applications such as drug delivery. In this study, the variables impacting on liposome formation during cubosome production were interrogated. Bottom-up (BU) and top-down (TD) approaches were employed to prepare submicron sized liquid crystalline dispersions (cubosomes) of phytantriol in water with varying amounts of Pluronic(®)F127 (F127) as a stabilizer. In the BU approach, ethanol was used as a hydrotrope and was later removed using a rotary evaporator, whereas in the TD approach the bulk liquid gel was dispersed using ultrasonication. We aimed at finding the optimum ratio of phytantriol-to-F127 resulting in stable, liposome-free dispersions, whether this depends on the preparation method and the resulting morphology of the particles. The average particle size and zeta potential of the samples were measured using dynamic light scattering (DLS). Cryogenic transmission electron microscopy (Cryo-TEM) images showed a substantial number of liposomes in addition to cubosomes in the dispersion containing 4-1 (w/w) phytantriol-to-F127 prepared by the BU approach compared to very low liposome content with the TD approach. The effects of the amount of F127 in both approaches, amount of ethanol on the BU method and temperature on the TD method were investigated using small-angle X-ray scattering (SAXS). The cubosomes displayed cubic double-diamond (Pn3m) internal structure with a lattice parameter of approximately 6nm. In summary using the TD approach, with 4:1 phytantriol:F127 provided stable cubosome dispersion with minimal liposome co-existence.