Neutral and acid-adapted fatty acid vesicles of conjugated linoleic acid

Design of oleic acid/alkyl glycoside composite vesicles as cosmetics carrier: stability, skin permeability and antioxidant activity

Biocompatible fatty acids are natural biological materials which exhibit widespread biomedical applications. Nevertheless, their application in vesicle forms is hampered by strong pH sensitivity and poor stability to changes in ionic strength, temperature, and storage. In the investigation, the incorporation of alkyl glycoside (APG), a surfactant with non-ionic properties, into the oleic acid (OA) vesicles was undertaken as a means to address this issue. The newly formed OA/APG composite vesicles form in a pH range of between 5.4 and 7.4, which is close to the pH range of the physiological environment. The stability studies results showed that the OA/APG composite vesicles have excellent stability in terms of ionic strengths, temperature and storage. The formation of NAR-loaded OA/APG composite vesicles was demonstrated through FT-IR, DSC and XRD. In vitro topical delivery and skin retention studies confirmed that the composite vesicles improve skin permeation rate and have better skin permeation behavior. Antioxidant activity experiments confirmed that the antioxidant effect composite vesicles were significantly increased as compared to the naringenin (NAR). This finding has theoretical implications for the use of drug-loaded fatty acid vesicles in cosmetics industries and topical delivery systems.

Efficient removal of heavy metals in water utilizing facile cross-link conjugated linoleic acid micelles

Micellar-enhanced ultrafiltration (MEUF) technology is an effective method to treat low-concentration heavy metal wastewater. However, the leakage of surfactants in the ultrafiltration (UF) process will inevitably cause secondary pollution. In this study, a biosurfactant of conjugated linoleic acid (CLA) with conjugated double bonds was selected to bind its micelles by simple thermal crosslinking to obtain morphologically stable stearic acid (SA) nanoparticles. The pure SA nanoparticles were obtained by repeated dialysis. The stability of the SA nanoparticles was verified by comparing the particle size distribution and solubility of the materials before and after crosslinking at different pH levels. The effectiveness of SA nanoparticle-enhanced UF in removing heavy metals was verified by exploring the adsorption performance of SA nanoparticles. The dialysis device was used to simplify the UF device, wherein SA nanoparticles were assessed as adsorbents for the elimination of Cu2+, Pb2+, and Cd2+ ions from aqueous solutions under diverse process parameters, including pH, contact time, metal ion concentration, and coexisting ions. The findings indicate that the SA nanoparticles have no evidence of secondary contamination in UF and exhibit compatibility with a broad pH range and coexisting ions. The maximum adsorption capacities for Cu2+, Pb2+, and Cd2+ were determined to be 152.77, 403.56, and 271.46 mg/g, respectively.

The incorporated hydrogel of chitosan-oligoconjugated linoleic acid vesicles and the protective sustained release for curcumin in the gel

Assemblies of as called "chitosan hydrogel-liposome" are expected for overcoming the burst effect in drug release from chitosan (CS) hydrogels. Herein, a hydrogel delivery system made of chitosan incorporated fatty acid vesicles was constructed for protective sustained release of curcumin (Cur). The curcumin was encapsulated in the prepared oligo-conjugated linoleic acid vesicles (OCLAVs), and then the drug-embedded vesicles were constructed to Cur-OCLAVs-CS hydrogels with CS solution. The fabricated Cur-OCLAVs-CS hydrogel was fluidic at room temperature and could be rapidly gelled at 37 °C. Morphology study proves that the OCLAVs stayed as nano-vesicles in the gel. The Cur-OCLAVs-CS hydrogels effectively declined the burst effect with enhanced antioxidant activity. The Cur (400 μM)-OCLAVs-CS gel presented a cumulative release rate of 51.23 % of curcumin in 96 h, comparing to 93.37 % of that from the Cur-CS gel. Moreover, the corporation of OCLAVs and CS made the gel exhibited strong synergistic effect on the antioxidant activity, with an enhancement of up to 148.1 % on the ferric reducing power. Therefore, the hydrogel carrier made of incorporated fatty acid vesicles-chitosan can be served as an injectable or 3D printable drug delivery system, which may provide a hint to overcome the burst effect that existed in chitosan and other polysaccharide-based gels.

Micron and nano hybrid ufasomes from conjugated linoleic acid, their vesiculation and encapsulation of ginsenoside Rg3

BACKGROUND

Unsaturated fatty acids used to form unstable micro-vesicles, while conjugate linoleic acid (CLA)-sodium dodecyl sulfate (SDS) can self-assembly to stable nano-conjugate linoleic acid vesicles (nano-CLAVs). Generally, micro-capsule could geometrically provide higher loading capacity but also generate concerns in construction convenience, sustained release, bioaccessibility and stability. Hence there is a contradiction between loading capacity and encapsulation efficiency. Therefore, the study of the factors that decide the capsule size falling in nano or micron size with same capsule material would be a benefit to food or drug delivery science.

RESULTS

The micron- and nano-CLAVs were constructed for encapsulation and sustained release of ginsenoside Rg3. The formation mechanism of nano or micron capsule,s the effect of vesicle sizes on encapsulation efficiency, drug loading efficiency and stability of the encapsulated Rg3 were investigated. It was found that with the addition of salt (PBS), the size of CLAVs jumped from nano to micron. Furthermore, the salt concentration is the key factor that decides the vesicle size of nano or micron. The pH at fabrication triggers the vesiculation and dramatically affects the vesicle size over the nano and micron scales.

CONCLUSION

Compared to the nano-CLAVs, micron vesicles enhanced the loading capacity to 137.6% and the encapsulation efficiency to 138.4%, respectively. Meanwhile, the micron-CLAVs performed similar sustained release of Rg3 as the nano-CLAVs did, and was stable for 120 days at room temperature or sustained 98.9% of capsules after centrifuge at 6090 × g for 20 min. © 2022 Society of Chemical Industry.

pH-Tolerant giant vesicles composed of cationic lipids with imine linkages and oleic acids

Giant vesicles (GVs) have attracted attention as functional materials because they can encapsulate both hydrophilic and hydrophobic compounds. For next generation functional GVs, both tolerance and stimuli-sensitivity are needed. So far, vesicles tolerant to acidic or basic conditions were generated using a mixture of cationic lipids and fatty acids. Here, to create functional GVs that are tolerant to a wide pH range but sensitively respond at below a specific pH, the behaviour of GVs composed of a cationic lipid with an imine bond and oleic acid was investigated. Even though the GVs prepared by the film swelling method were tolerant to strongly acidic conditions, GVs without oleic acid gradually shrank, accompanied by the generation of oil droplets at the same pH. ¹H NMR analysis revealed that during hydration of the film, the imine bond hydrolysed to provide a cationic surfactant and an oil component in the presence of oleic acid due to its own Lewis basicity, suggesting the dissociation of oleic acid. The results of fluorescence spectroscopy using an environment-responsive probe and IR spectroscopy indicated that the GV tolerance originated from the intermolecular interactions of cationic lipids and anionic oleate.

Giant vesicles composed of cationic lipids having an imine linkage and oleic acid were stable at strong acidic conditions.

Surfactant-Induced Self-Assembly of CdTe Quantum Dots into Multicolor Luminescent Hybrid Vesicles

Here, we report the interaction of mercaptosuccinic acid (MSA)-capped CdTe quantum dots (QDs) with hexadecyltrimethylammonium bromide (CTAB) surfactant and subsequent formation of self-assembled multicolor luminescent vesicles in aqueous medium. A continuous phase sequence from clear (C1) to turbid (T1), precipitate (P), turbid (T2), and clear (C2) has been observed for QD solution upon increasing the concentration of positively charged CTAB, indicating dynamic equilibrium between various self-assembled supramolecular structures. In contrast, no such changes have been observed in the presence of negatively charged sodium dodecyl sulfate and neutral Triton X-100 surfactants, indicating specific electrostatic interactions behind the observed phase separation behavior. Epi-fluorescence imaging in the C1 and C2 regions reveals the presence of surfactant-induced aggregates of QD. The morphologies and photoluminescence properties of self-assembled supramolecular structures in the T1 and T2 region have been explored by using scanning electron microscopy (SEM), atomic force microscopy (AFM), and confocal laser scanning microscopy (CLSM). SEM and AFM images reveal distinct spherical vesicles in the T1 and T2 regions of the binary mixture. Moreover, CLSM results show that these spherical vesicles are inherently luminescent due to the presence of self-assembled QDs. Fabrication of multicolor luminescent vesicles has been demonstrated by tuning the size of CdTe QD. Using CLSM, we have further demonstrated efficient encapsulation of Rhodamine 6G dye into these self-assembled vesicles without any structural disruption. While these luminescent vesicles are quite stable in neutral and basic pH (pH = 6.5-11), they are unstable in acidic pH (pH = 4.5-5.5). Moreover, it has been observed that this pH-responsive structural change is totally reversible. The present findings of self-assembled luminescent vesicles from QD-CTAB binary mixture may open up new opportunities in various applications such as bioimaging, drug delivery, and sensing.

Controlling Foam Stability with the Ratio of Myristic Acid to Choline Hydroxide

The interfacial and foam properties of a model system based on the mixture between myristic acid and choline hydroxide have been investigated as a function of the molar ratio ( R) between these two components and temperature. The aim of this study was to obtain insight on the links between the self-assemblies in bulk and in the foam liquid channels, the surfactant packing at the interface, and the resulting foam properties and stability. A multiscale approach was used combining small angle neutron scattering, specular neutron reflectivity, surface tension measurements, and photography. We highlighted three regimes of foam stability in this system by modifying R: high foam stability for R < 1, intermediate at R ∼ 1, and low for R > 1. The different regimes come from the pH variations in bulk linked to R. The pH plays a crucial role at the molecular scale by setting the ionization state of the myristic acid molecules adsorbed at the gas-liquid interface, which in turn controls both the properties of the monolayer and the stability of the films separating the bubbles. The main requirement to obtain stable foams is to set the pH close to the p K_a in order to have a mixture of protonated and ionized molecules giving rise to intermolecular hydrogen bonds. As a result, a dense monolayer is formed at the interface with a low surface tension. R also modifies the structure of self-assembly in bulk and therefore within the foam, but such a morphological change has only a minor effect on the foam stability. This study confirms that foam stability in surfactant systems having a carboxylic acid as polar headgroup is mainly linked to the ionization state of the molecules at the interface.