Effect of oleic acid on the properties of protein adsorbed layers at water/oil interfaces: An EPR study combined with dynamic interfacial tension measurements

Encapsulation of cannabidiol in oil-in-water nanoemulsions and nanoemulsion-filled hydrogels: A structure and biological assessment study

HYPOTHESIS

Lipophilic cannabidiol can be solubilized in oil-in water nanoemulsions, which can then be impregnated into chitosan hydrogels forming another colloidal system that will facilitate cannabidiol's release. The delivery from both systems was compared, alongside structural and biological studies, to clarify the effect of the two carriers' structure on the release and toxicity of the systems.

EXPERIMENTS

Oil-in-water nanoemulsions (NEs) and the respective nanoemulsion-filled chitosan hydrogels (NE/HGs) were formulated as carriers of cannabidiol (CBD). Size, polydispersity and stability of the NEs were evaluated and then membrane dynamics, shape and structure of both systems were investigated with EPR spin probing, SAXS and microscopy. Biocompatibility of the colloidal delivery systems was evaluated through cytotoxicity tests over normal human skin fibroblasts. An ex vivo permeation protocol using porcine ear skin was implemented to assess the release of CBD and its penetration through the skin.

FINDINGS

Incorporation of the NEs in chitosan hydrogels does not significantly affect their structural properties as evidenced through SAXS, EPR and confocal microscopy. These findings indicate the successful development of a novel nanocarrier that preserves the NE structure with the CBD remaining encapsulated in the oil core while providing new rheological properties advantageous over NEs. Moreover, NE/HGs proved to be more efficient as a carrier for the release of CBD. Cell viability assessment revealed high biocompatibility of the proposed colloids.

Study and optimization of oil-in-water emulsions formulated by low- and high-frequency ultrasounds

OBJECTIVE

A combined treatment using both low-frequency (20 kHz) and high-frequency ultrasounds (1.63 MHz) is a promising new process to stabilize emulsions with minimalist formulation. In order to optimize process parameters, a Doehlert experimental design was performed with oil-in-water emulsions, presently used for cosmetic products, composed of water, caprylic/capric triglycerides and oleic acid.

METHODS

Effects of treatment time, oil content and oleic acid content were studied on emulsion properties (droplet size, polydispersity index, ζ-potential and yield of oil incorporation) and on emulsion stability after a 28-day storage (creaming index, Turbiscan stability index (TSI) and oil release).

RESULTS

From experimental data, a model was established that allowed to study effects of each parameter and their interactions on emulsion formation and stability. Oleic acid content had a great impact on emulsion formation: It reduced droplet size, PDI and ζ-potential and increased yield of oil incorporation. However, a critical value could be highlighted, beyond which oleic acid effects reversed. Treatment time had an important beneficial effect on emulsion stability as it decreased creaming index, TSI and oil release after 28 days of storage. Oil content had a negative effect on emulsion formation and on emulsion stability. However, treatment time and oil content often had a beneficial synergistic effect.

CONCLUSION

The optimized conditions for emulsion processing were obtained through a desirability approach. They were experimentally validated.

The Impact of the Oil Phase Selection on Physicochemical Properties, Long-Term Stability, In Vitro Performance and Injectability of Curcumin-Loaded PEGylated Nanoemulsions

A nanotechnology-based approach to drug delivery presents one of the biggest trends in biomedical science that can provide increased active concentration, bioavailability, and safety compared to conventional drug-delivery systems. Nanoemulsions stand out amongst other nanocarriers for being biodegradable, biocompatible, and relatively easy to manufacture. For improved drug-delivery properties, longer circulation for the nanoemulsion droplets should be provided, to allow the active to reach the target site. One of the strategies used for this purpose is PEGylation. The aim of this research was assessing the impact of the oil phase selection, soybean or fish oil mixtures with medium chain triglycerides, on the physicochemical characteristics and injectability of curcumin-loaded PEGylated nanoemulsions. Electron paramagnetic resonance spectroscopy demonstrated the structural impact of the oil phase on the stabilizing layer of nanoemulsions, with a more pronounced stabilizing effect of curcumin observed in the fish oil nanoemulsion compared to the soybean oil one. The design of the experiment study, employed to simultaneously assess the impact of the oil phase, different PEGylated phospholipids and their concentrations, as well as the presence of curcumin, showed that not only the investigated factors alone, but also their interactions, had a significant influence on the critical quality attributes of the PEGylated nanoemulsions. Detailed physicochemical characterization of the NEs found all formulations were appropriate for parenteral administration and remained stable during two years of storage, with the preserved antioxidant activity demonstrated by DPPH and FRAP assays. In vitro release studies showed a more pronounced release of curcumin from the fish oil NEs compared to that from the soybean oil ones. The innovative in vitro injectability assessment, designed to mimic intravenous application, proved that all formulations tested in selected experimental setting could be employed in prospective in vivo studies. Overall, the current study shows the importance of oil phase selection when formulating PEGylated nanoemulsions.

Contrastive Study of the Foaming Properties of N-Acyl Amino Acid Surfactants with Bovine Serum Albumin and Gelatin

A detailed study on the foamability, foam stability, foam liquid-carrying capacity, and foam morphology of two N-acyl amino acid surfactants with bovine serum albumin (BSA) and gelatin were performed by foam scanning. The results showed that the foamability of the mixed system increased gradually and then tended to be stable with increasing surfactant concentration. The foamability of the high-concentration BSA system was stronger than that of the low-concentration BSA system. The foamability and foam stability of sodium N-lauroyl phenylpropanoic acid (N-C₁₂P)/BSA were better than those of sodium N-lauroyl propylamino acid (N-C₁₂A)/BSA, and the foamability and foam stability of N-C₁₂A/gelatin was better than those of N-C₁₂P/gelatin. The liquid-carrying capacity of the foam initially increased and then decreased with increasing time, and the maximum liquid-carrying capacity increased with increasing surfactant concentration. When the concentration of the surfactant was 8 mM, the drainage rate of N-C₁₂A/protein was higher than that of N-C₁₂P/protein. The morphology of the bubble gradually changed from spherical to polyhedron and the number of bubbles gradually decreased with time increasing. Differences in surfactant structure and protein type had an important effect on the number and area of foam.

Soy glycinin-soyasaponin mixtures at oil-water interface: Interfacial behavior and O/W emulsion stability

Soy glycinin (11S) was mixed with soyasaponin (Ssa) to elucidate the mechanism(s) involved in the stabilization of emulsions by mixed systems based on dynamic interfacial tension and dilatational rheology at the oil-water interface. The short/long-term properties of oil-in-water emulsions stabilized by 11S-Ssa mixtures included droplet-size distribution, droplet ζ-potential, microstructure, and Turbiscan stability index. The combination of Ssa (0.05%) with 11S significantly affected the interfacial dilatational and emulsion properties although the interfacial properties were still dominated by the protein. Higher concentrations (0.1% and 0.2%) of Ssa combined with 11S synergistically decreased the interfacial tension, which was attributed to the interaction between 11S and Ssa. Using high Ssa concentrations (0.25%-0.5%) enhanced the long-term stability of emulsions (in response to external deformations) after 42 d. These results will aid the basic understanding of protein-Ssa interfacial adsorption during emulsion formation and can help prepare natural food additives for designing emulsions.

Interaction Mechanism of Different Surfactants with Casein: A Perspective on Bulk and Interfacial Phase Behavior

Understanding the interaction mechanism between proteins and surfactants is conducive to the application of protein/surfactant mixtures in the food industry. The present study investigated the interaction mechanism of casein with cationic Gemini surfactant (BQAS), anionic Gemini surfactant (SGS), anionic single-chain surfactant (sodium dodecyl sulfate [SDS]), and two biosurfactants (rhamnolipid [RL] and lactone sophorolipid [SL]) at the interface and in bulk phase. BQAS/casein and SDS/casein mixtures exhibit a strong synergistic effect on the surface activity. For SGS, RL, and SL, the formation of surfactant/casein complexes caused no improvement in surface activity. Dilational elasticity results indicate the displacement of casein by SGS, RL, and SL at the surface. However, the BQAS/casein complexes manifested varying dilational properties from pure casein surface. The strong electrostatic interaction between BQAS and casein produced large-size precipitate particles. For other surfactants, no precipitate particles formed. Determination of ζ-potential, UV-vis absorption spectra, and fluorescence spectra demonstrated the stronger interaction of BQAS and SDS with casein than that of SGS, RL, and SL. Addition of BQAS initially increased and then decreased the α-helix structure of casein. For SGS, RL, and SL, no noticeable change occurred in the casein structure. However, the formation of SDS/casein complexes was conducive to the casein structure. In conclusion, the interaction between BQAS and casein is similar to that of cationic single-chain surfactant. Furthermore, SGS exhibits a significantly different interaction mechanism from the corresponding monomer (SDS), possibly resulting from its excellent interfacial activity, low critical micelle concentration values, and strong self-assembly capability. For RL and SL, the weak interaction is attributed to the relatively complicated structure and less charged degree of hydrophilic headgroups.