Cyclodextrin-based Pickering emulsions: functional properties and drug delivery applications

Pickering emulsion stabilized by quercetin-β-cyclodextrin-diglyceride particles: Effect of diglyceride content on interfacial behavior and emulsifying property of complex particles

This research develops diacylglycerol (DAG) based Pickering emulsions with enhanced oxidative stability stabilized by self-assembled quercetin/DAG/β-cyclodextrin (β-CD) complexes (QDCCs) using a one-step agitation method. Influence of DAG content (5%, 15%, 40%, and 80%, w/w) on the self-assembly behavior, interfacial properties, and emulsifying ability of complex particles was investigated. SEM, XRD and ATR-FTIR studies confirmed the formation of ternary composite particles. QDCCs in 80% DAG oil had the highest quercetin encapsulation efficiency (6.09 ± 0.01%), highest DPPH radical scavenging rate and ferric reducing antioxidant property (FRAP). β-CD and quercetin adsorption rates in emulsion with 80% DAG oil were 88.4 ± 2.53% and 98.34 ± 0.15%, respectively. Pickering emulsions with 80% DAG had the smallest droplet size (8.90 ± 1.87 μm) and excellent oxidation stability. This research develops a novel approach to regulate the physicochemical stability of DAG-based emulsions by anchoring natural antioxidants at the oil-water interface through a one-pot self-assembly method.

Polyaromatic Hydrocarbon Inclusion Complexes with 2-Hydroxylpropyl-β/γ-Cyclodextrin: Molecular Dynamic Simulation and Spectroscopic Studies

In aqueous and solid media, 2-HP-β/γ-CD inclusion complexes with poly aromatic hydrocarbon (PAH) Phenanthrene (PHN), Anthracene (ANT), Benz(a)pyrene (BaP), and Fluoranthene (FLT) were investigated for the first time. The inclusion complexes were characterized and investigated using fluorescence and 1HNMR spectroscopy. The most prevalent complexes consisting of both guests and hosts were those with a 1:1 guest-to-host ratio. The stability constants for the complexes of PHN with 2-HP-β-CD and 2-HP-γ-CD were 85 ± 12 M-1 and 49 ± 29 M-1, respectively. Moreover, the stability constants were found to be 502 ± 46 M-1 and 289 ± 44 M-1 for the complexes of ANT with both hosts. The stability constants for the complexes of BaP with 2-HP-β-CD and 2-HP-γ-CD were (1.5 ± 0.02) × 103 M-1 and (9.41 ± 0.03) × 103 M-1, respectively. The stability constant for the complexes of FLT with 2-HP-β-CD was (1.06 ± 0.06) × 103 M-1. However, FLT was observed to form a weak complex with 2-HP-γ-CD. Molecular dynamic (MD) simulations were used to investigate the mechanism and mode of inclusion processes, and to monitor the atomic-level stability of these complexes. The analysis of MD trajectories demonstrated that all guests formed stable inclusion complexes with both hosts throughout the duration of the simulation time, confirming the experimental findings. However, the flexible Hydroxypropyl arms prevented the PAHs from being encapsulated within the cavity; however, a stable exclusion complex was observed. The main forces that influenced the complexation included van der Waals interactions, hydrophobic forces, and C-H⋯π interaction, which contribute to the stability of these complexes.

γ-Cyclodextrin-based metal-organic frameworks for lactonic sophorolipid application in enhanced oil recovery

Lactonic sophorolipid (LSL) exhibits numerous surfactant activities, such as emulsification, wetting action, dispersion effect, and oil-washing activities. Nevertheless, LSLs have poor water solubility, which restrains their application in the petroleum industry. In this research, a new compound, lactonic sophorolipid cyclodextrin metal-organic framework (LSL-CD-MOFs), was obtained by loading LSL into γ-cyclodextrin metal-organic frameworks (γ-CD-MOFs). The LSL-CD-MOFs were characterized by N₂ adsorption analysis, X-ray powder diffraction analysis, Fourier transform infrared spectroscopy, and thermogravimetric analysis. Loading LSL into γ-CD-MOFs significantly increased the apparent water solubility of LSL. However, the critical micelle concentration of LSL-CD-MOFs was similar to that of LSL. Furthermore, LSL-CD-MOFs effectively reduced the viscosities and improved the emulsification indices of oil-water mixtures. Oil-washing tests, which were conducted using oil sands, revealed that the LSL-CD-MOFs yielded an oil-washing efficiency of 85.82 % ± 2.04 %. Overall, γ-CD-MOFs are promising carriers for LSL, and LSL-CD-MOFs are a potential, low-cost, new, green surfactant for enhanced oil recovery.

Pickering Emulsion Stabilized by β-Cyclodextrin and Cinnamaldehyde/β-Cyclodextrin Composite

A Pickering emulsion was prepared using β-cyclodextrin (β-CD) and a cinnamaldehyde (CA)/β-CD composite as emulsifiers and corn oil, camellia oil, lard oil, and fish oil as oil phases. It was confirmed that Pickering emulsions prepared with β-CD and CA/β-CD had good storage stability. The rheological experiments showed that all emulsions had G' values higher than G″, thus confirming their gel properties. The results of temperature scanning rheology experiments revealed that the Pickering emulsion prepared with β-CD and CA/β-CD composites had high stability, in the range of 20-65 °C. The chewing properties of Pickering emulsions prepared by β-CD and corn oil, camellia oil, lard, and herring oil were 8.02 ± 0.24 N, 7.94 ± 0.16 N, 36.41 ± 1.25 N, and 5.17 ± 0.13 N, respectively. The chewing properties of Pickering emulsions made with the CA/β-CD composite and corn oil, camellia oil, lard, and herring oil were 2.51 ± 0.05 N, 2.56 ± 0.05 N, 22.67 ± 1.70 N, 3.83 ± 0.29 N, respectively. The texture properties confirmed that the CA/β-CD-composite-stabilized-emulsion had superior palatability. After 28 days at 50 °C, malondialdehyde (MDA) was detected in the emulsion. Compared with the β-CD and CA + β-CD emulsion, the CA/β-CD composite emulsion had the lowest content of MDA (182.23 ± 8.93 nmol/kg). The in vitro digestion results showed that the free fatty acid (FFA) release rates of the CA/β-CD composite emulsion (87.49 ± 3.40%) were higher than those of the β-CD emulsion (74.32 ± 2.11%). This strategy provides ideas for expanding the application range of emulsifier particles and developing food-grade Pickering emulsions with antioxidant capacity.

Modulating hydrophilic properties of β-cyclodextrin/carboxymethyl cellulose colloid particles to stabilize Pickering emulsions for food 3D printing

This research investigated edible Pickering emulsions stabilized by polysaccharide complexes as inks for food 3D printing. The interface membrane structure in the Pickering emulsion system was formed using complexes consisting of β-cyclodextrin (β-CD) and carboxymethyl cellulose (CMC). Except for provide sufficient steric barrier and electrostatic repulsion to increase the stability of the Pickering emulsions, the interface membrane constructs also can demonstrate good biphasic wettability and lower oil/water interfacial tension. The hydrophilicity of complexes (β-CD/CMC) was mainly adjusted by the ratio of β-CD/CMC (R_β/C) and the substitution degree (DS) of CMC, which further adjusted the physical and chemical properties of Pickering emulsion to make it correspond to the rheological behavior applied to 3D printing. The stable Pickering emulsion (R_β/C = 2:2, DS = 1.2, weight ratio of oil phase (φ) = 65 %) displayed excellent printing potential by characterizations analysis of Pickering emulsions. The smoothness, viscosity, and self-supporting ability of the Pickering emulsion under the optimized conditions were further analyzed using a filling density printing experiment of a cuboid model. The emulsifying properties of β-CD were adjusted by hydrophilic CMC to achieve the required amphipathic properties of the complexes to develop Pickering emulsions for food 3D printing.

Pickering emulsions stabilized by β-CD microcrystals: Construction and interfacial assembly mechanism

β-Cyclodextrin (β-CD) can combine with oil and other guest molecules to form amphiphilic inclusion complexes (ICs), which can be adsorbed on the oil-water interface to reduce the interfacial tension and stabilize Pickering emulsions. However, the subtle change of β-CD in the process of emulsion preparation is easily ignored. In this study, β-CD and ginger oil (GO) were used to prepare the Pickering emulsion by high-speed shearing homogenization without an exogenous emulsifier. The stability of the emulsion was characterized by microscopic observation, staining analysis, and creaming index (CI). Results showed that the flocculation of the obtained Pickering emulsion was serious, and the surface of the droplets was rough with lamellar particles. In order to elucidate the formation process of the layered particles, the GO/β-CD ICs were further prepared by ball milling method, and the X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), and interfacial tension analyses found that β-CD and GO first formed amphiphilic nanoscale small particles (ICs) through the host-guest interaction, and the formed small particles were further self-assembled into lamellar micron-scale amphiphilic ICs microcrystals. These amphiphilic ICs and microcrystals aggregated at the oil-water interface and finally formed the Pickering emulsion. In this study, by exploring the formation process and evolution of GO/β-CD self-assembly, the formation process and stabilization mechanism of the β-CD-stabilized GO Pickering emulsion were clarified preliminarily, with the aim of providing a theoretical basis for the development of high-performance CD-stabilized Pickering emulsions.

Drug-Loaded Nanocarriers Composed of Cholesteryl Oleate Crystal Cores and Multiple-Nanosheet Shells of γ-Cyclodextrin Inclusion Complex Crystals

In this study, we prepared drug-loaded nanocarriers made of cholesteryl oleate (ChO) and γ-cyclodextrin (γ-CD). A nanosuspension (nanosuspension-I, NS-I) containing nanoparticles with a mean size of approximately 170 nm was obtained through the solvent-diffusion method using ethanol. A second nanosuspension (nanosuspension-II, NS-II), which was prepared by freeze-drying and redispersion of NS-I, exhibited an increased particle size of approximately 210 nm. Cryogenic transmission electron microscopy (cryo-TEM) and atomic force microscopy (AFM) force-distance curves indicated that the nanoparticles in NS-I were oblong and soft. However, those in NS-II were angular and stiff, and, interestingly, multiple nanosheets covered the solid-liquid interface. Synchrotron wide-angle X-ray diffraction (WAXD) analysis of NS-II indicated that the nanoparticles in it had a core-shell structure, where the ChO crystal in the inner core was covered by multiple nanosheets of ChO/γ-CD inclusion complex crystals. The X-ray peak analysis suggested that the γ-CD columns of the nanosheets were vertically stacked onto the ChO crystal interface. It was found that the nanosheets on the nanoparticle interface were formed during the freezing process. A model drug carbamazepine (CBZ) was loaded into the ChO/γ-CD nanoparticles by pre-dissolving CBZ in ethanol during the solvent-diffusion process. Cryo-TEM, ¹H NMR, ζ-potentials, and synchrotron WAXD indicated that CBZ was unexpectedly loaded into the shell as a CBZ/γ-CD inclusion complex crystalline nanosheet. The specific nanosheet structure, where ChO and CBZ coexisted in the same crystal of γ-CD, could achieve CBZ loading in the nanoparticles. ChO/γ-CD nanoparticles with the unique core-shell structure are expected to perform as practical carriers for drug delivery.

Green Nanoemulsion Stabilized by In Situ Self-Assembled Natural Oil/Native Cyclodextrin Complexes: An Eco-Friendly Approach for Enhancing Anticancer Activity of Costunolide against Lung Cancer Cells

Lung cancer is the second-most deadly malignancy worldwide, of which smoking is considered a major risk factor and causes 75–80% of lung cancer-related deaths. Costunolide (CTD) extracted from plant species Saussurea, Aucklandia, and Inula exhibits potent anticancer properties, specifically in lung cancer and leukemia. Several nanoemulsions were prepared and optimized using a three-factor Box–Behnken experimental design. The optimized green nanoemulsion (GNE) showed a vesicle size of 199.56 nm. The IC₅₀ values revealed that A549 cells were significantly more sensitive to the optimized CTD formula than the plain formula and raw CTD. A cell cycle analysis revealed that the optimized CTD formula treatment resulted in significant cell cycle arrest at the S phase. The results also indicated that treatment with the CTD formula significantly increased caspase-3, Bax, Bcl-2, and p53 mRNA expression compared to the plain formula and CTD raw. In terms of the inflammatory markers, the optimized formula significantly reduced the activity of TNF-α and NF-κB in comparison with the plain formula and raw drug only. Overall, the findings from the study proved that a CTD GNE formulation could be a promising therapeutic approach for the treatment of lung cancer.