Outer Water Phase Research Articles

W/O/W Pickering emulsions stabilized by complex modified phycocyanin.

A water-in-oil-in-water (W/O/W) double emulsion can simultaneously load hydrophilic and hydrophobic substances due to its unique two-membrane, three-phase structure. However, thermodynamic instability greatly limits the application of double emulsions in food processing. Further development of Pickering emulsions based on proteins, etc., can improve the stability and loading capacity. It is of great significance to promote their practical application. Herein, we prepared ultrasound pretreatment complex glycation-modified phycocyanin (UMPC) to stabilize a W/O/W Pickering emulsion for the codelivery of vitamin B12 (VB12) and vitamin E (VE). First, an inner water phase and oil phase containing polyglycerin polyricinoleate were homogenized to prepare a W/O emulsion. Subsequently, the W/O emulsion was homogenized with an outer water phase containing UMPC to obtain a W/O/W Pickering emulsion. A gel-like inner phase emulsion with excellent storage and thermal stabilities was obtained under the condition that the W/O emulsion volume ratio was 80% and the UMPC was stabilized by 10 g kg-1. The double emulsion after loading VB12 and VE showed good encapsulation effect during the storage period, the encapsulation rate could reach more than 90%, it also showed excellent protection effect under long-time storage and UV irradiation and the retention rate increased by more than 65%. In addition, the bioavailability of VB12 and VE significantly increased during simulated gastrointestinal digestion and reached 46.02% and 52.43%, respectively. These results indicate that the UMPC-stabilized W/O/W Pickering emulsion is an effective carrier for the codelivery of hydrophilic and hydrophobic bioactive molecules and also provides a means for useful exploration of an efficient and stable emulsion system stabilized by biological macromolecules. © 2024 Society of Chemical Industry.

Improving salidroside stability using water-in-oil-in-water emulsion with whey protein isolate: Formation and characterization

A water-in-oil-in-water (W/O/W) emulsion for the encapsulation of salidroside (Sal) was constructed. This study aimed to detect the impact of whey protein isolate (WPI) on the microstructure and stability of Sal W/O/W emulsion, which was prepared by two-step emulsification. First, Sal and sodium alginate (SA) were added to the inner water phase, and polyglycerol polyricinoleate (PGPR) was added to the oil phase to prepare a water-in-oil (W/O) emulsion. Second, different concentrations of WPI were added to the outer water phase containing SA to prepare a Sal W/O/W emulsion. The microstructure, stability, moisture distribution, rheological properties, and encapsulation efficiency of Sal were detected. The results showed that the particle size and the size distribution range became smaller and narrower with increasing WPI concentration. When the concentration of WPI was greater than 2%, the double-layer structure remained stable over 28 days of storage at 4 °C. Moreover, when the WPI concentration reached 4%, the entrapment efficiency of Sal was the highest. These results indicated that the optimum concentration of WPI was 4%.

Fabrication and stability of W/O/W emulsions stabilized by gum arabic and polyglycerol polyricinoleate.

In order to study the effect of adsorption of surfactant at the two interfacial layers on emulsion stability, the kinetically stable water-in-oil-in-water (W/O/W) emulsion carriers were prepared using polyglycerol polyricinoleate (PGPR) and gum arabic (GA) as emulsifiers. The relationship between the adsorption of the surfactant and the stability mechanism of the emulsions was elucidated. When the contents of PGPR and GA were low, the interfaces between oil and the inner and outer water phases, respectively, could not be completely covered. However, when the concentration of PGPR was higher than 60 g kg-1 , the excess PGPR was adsorbed on the interface between the oil phase and the outer water phase. When the concentration of GA reached 80 g kg-1 , more GA was adsorbed to the oil-in-water interface. Moreover, the presence of PGPR on the interface could reduce the adsorption capacity of GA. Two types of kinetically stable emulsions were obtained by optimizing the interface composition (60 g kg-1 GA/80 g kg-1 PGPR and 60 g kg-1 PGPR/80 g kg-1 GA). The kinetically stable W/O/W emulsions prepared in this study were successfully used to encapsulate a hydrophilic vitamin (vitamin B12) with an encapsulation efficiency (EE) of 80% and release efficiency (RE) of 95%. The interfacial adsorption GA can accelerate the hydrolysis of fat. Overall, this study provides a new strategy for the preparation of W/O/W emulsions, which might be beneficial for application in food, cosmetic, chemical, and pharmaceutical industries. © 2023 Society of Chemical Industry.

Preparation of pH sensitive bacteriostatic W/O/W emulsion microcapsules

This experiment was done to study the zeolite molecular sieve as a drug-binding effector, the non-antibiotic drug potassium diformate uniformly disperse in the internal aqueous phase of the 'egg box' structure formed by pectin-calcium ions. With oil phase as the intermediate phase and Xanthan gum Chitosan as the external water phase, the W/O/W type sustained release bacteriostatic microcapsules with pH response were prepared and characterized by Fourier transform infrared, thermogravimetric, SEM, and TEM. It can be obtained through characterization experiments that the inner water phase, oil phase, and outer water phase were formed by observation, and W/O/W emulsion microcapsules were obtained and the bacteriostasis effect of microcapsules was verified by bacteriostasis experiment. The permeance experiment showed that the molecular sieve was successfully coated in the microsphere. Studying on drug release mechanism and sustaining release performance of composite emulsion microcapsules. In vitro drug release study showed that the encapsulation efficiency and drug loading rate of microcapsules were improved by adding molecular sieve, reaching 12.31% and 61.55%, respectively. At the same time, we observed that the drug release rate slowed down during the simulated intestinal release process, and the drug release kinetics were in line with the first-order kinetic model and Ritger-Peppas model equation. Experiments had proven that the drug-loaded microcapsules exerted a significant bacteriostatic effect on Escherichia coli, Staphylococcus aureus, and Bacillus subtilis, with the highest antibacterial rates of 97.25%, 94.05%, and 95.93%, respectively. Therefore, the composite emulsion microcapsules can be used as a new controlled-release drug delivery system in vivo.

Studying the Marangoni effect in double emulsions with a hybrid multi-relaxation time lattice Boltzmann method–finite difference method

Two-phase mass transfer is a critical process in preparing the inertial confinement fusion target microsphere. It is essential to reveal the effect of Marangoni convection on the flow and mass transfer in double emulsions to prepare high-quality microspheres. This paper develops a two-dimensional two-phase flow and mass transfer model based on multi-relaxation time lattice Boltzmann method and finite difference method. The study of the Marangoni effect within the double emulsion under a shear flow is carried out. The results indicate that the slope parameter (which measures the sensitivity of surface tension to the variation of solvent) and initial solvent concentration crucially affect the mass transfer behavior and the magnitude of the Marangoni convection of double emulsions. When the slope parameter is zero, there is no Marangoni convection in the flow field, the magnitude of the vorticity field is minimal, and solvent diffuses uniformly and slowly to the outer water phase. However, at low values of slope parameter, the Marangoni vortex formed within the emulsion is weak, and few plumes appear in the concentration field; at higher values, the magnitude of the vorticity field increases, and a large number of plumes appear and merge. Compared with the slope parameter, the mass transfer process is less sensitive to the initial solvent concentration. Plumes appear and merge at three different initial solvent concentrations. The time required for double emulsions to develop into equilibrium is inversely proportional to the initial solvent concentration.

Influence of encapsulation variables on formation of leuprolide-loaded PLGA microspheres

Emulsion-based solvent evaporation microencapsulation methods for producing PLGA microspheres are complex often leading to empirical optimization. This study aimed to develop a more detailed understanding of the effects of process variables on the complex emulsification processes during encapsulation of leuprolide in PLGA microspheres using a high-shear rotor–stator mixer. Following extensive analysis of previously developed formulation conditions that yield microspheres of equivalent composition to the commercial 1-month Lupron Depot, multiple variables during the formation of primary and secondary emulsion were investigated with the aid of dimensional analysis, including: rotor speed (ω) and time (t), dispersed phase fraction (Φ) and continuous phase viscosity (µc). The dimensionless Sauter mean diameter (d3,2) of primary emulsion was observed to be proportional to the product of several key dimensionless groups (Φ1,We,Re,ω1t1) raised to the appropriate power indices. A new dimensionless group (Θ ) (surface energy/energy input) was used to rationalize insertion of a proportionate time dependence in the scaling of the d3,2. The dimensionless d3,2 of secondary emulsion was found proportional to the product of three dimensionless groups (Φ2,μ1′μc2,ω2t2) raised to the appropriate power indices. The increased viscosity of the primary emulsion, decreased secondary water phase volume and reduced second homogenization time each elevated encapsulation efficiency of peptide by reducing drug leakage to the outer water phase. These results could be useful for dimensional analysis and improving manufacturing of PLGA microspheres by the solvent evaporation method.

Fabrication of whey-protein-stabilized G/O/W emulsion for the encapsulation and retention of l-ascorbic acid and α-tocopherol

Water in oil in water (W1/O/W2) emulsion is a potential carrier for the simultaneous encapsulation of hydrophilic and lipophilic bioactive components. A major challenge of W1/O/W2 emulsion is its physical instability, due to the passage of water molecules from the inner to outer water phase. The gelation of the internal aqueous phase is a promising strategy for the stabilization of double emulsion. The current study aimed at fabrication of gelled water in oil in water (W/W) emulsion by cold-set gelation of pre-heated whey protein isolate (WPI) in inner aqueous phase induced by sodium chloride and its combination with l-ascorbic acid (L-AA) and addition of native WPI in the external aqueous phase. L-AA was not only used as a hydrophilic bioactive component but also a gelling agent. The formation and stabilization of gelled water in oil (G/O) and G/O/W emulsions were optimized by different compositions in the internal aqueous phase and emulsification methods and characterized in term of morphological structure and size distribution. All G/O/W emulsions showed Newtonian fluid behavior when they were developed using T-channel module and extrusion module with cellulose acetate membrane. The G/O/W emulsions had a size of 7.21–9.93 μm and kept multiple-compartment after storage. The co-encapsulation in G/O/W emulsions improved the stability of L-AA and α-tocopherol, with their retention being 76% at 25 °C after 15 days.

Encapsulation of amino acids in water-in-oil-in-water emulsions stabilized by gum arabic and xanthan gum

In this study, several kinds of amino acids were successfully encapsulated in a W1/O/W2 emulsion produced using a two-step emulsification process. Polyglycerol polyricinoleate (PGPR) was used as a hydrophobic emulsifier in the oil phase, while gum arabic (GA) and xanthan gum (XA) were used as an emulsifier and stabilizer in the outer water (W2) phase, respectively. The stability and encapsulation efficiency of the W1/O/W2 emulsions depended on the ratio of W1/O emulsion to W2 phase, as well as the concentration of GA and XA within the outer W2 phase. A W1/O/W2 emulsion prepared using 2 % (w/w) GA and 0.3 % (w/w) XA in the W2 phase exhibited good stability and a high encapsulation efficiency (>80 %) for several amino acids. As the hydrophobicity of amino acids and storage temperature increased, the leakage from the W1 to W2 phases increased, which can be attributed to increasing solubility in the oil phase. The encapsulation efficiency of lysine encapsulated in GA-XA-stabilized W1/O/W2 double emulsion was over 84 % after 28 days storage at 4 °C. These results indicate that double emulsions may be useful for the encapsulation of amino acids, which may be useful to protect them from their environment and mask bitter flavors.

Influence of Refractive Index Differences on the Signal Strength for Raman-Spectroscopic Measurements of Double Emulsion Droplets

Double emulsions show great potential for encapsulating active substances and protecting them against external influences. However, they tend to become unstable during storage. Research on double emulsions, therefore, focuses on maintaining their microstructure during their shelf life. Optical measurement methods, such as Raman spectroscopy, have hardly been used to date to analyze the microstructure of double emulsions, mainly due to multiple scattering effects. This study investigates the influence of refractive index matching of double emulsion phases by measuring the Raman signal strength of the inner water phase for different refractive index combinations. Ammonium nitrate and glycerol are added to the inner and outer water phase, respectively, to change the refractive indices of both phases. Additionally, polyvinyl alcohol serves as an emulsifier in the outer water phase. The oil phase consists of silicone oil and Dowsil Resin XR 0497 as the emulsifier. The refractive index of the oil phase is kept constant. For individual phase boundaries of single droplets, the refractive index matching plays a minor role. However, if there are many droplets with correspondingly numerous phase boundaries, which leads to multiple scattering during the measurement, the matching has a significant influence on the signal strength of the inner phase. When measuring double emulsions, the phases should always be matched, as this results in higher signals and improves the sensitivity of the measurement.

Meat systems produced with Monascus pigment water-in-oil-in-water multiple emulsion as pork fat replacers

Multiple emulsions have drawn great attentions from researchers in the production of low-fat foods. The Monascus pigment W/O/W multiple emulsions were prepared by a two-step emulsification procedure with Monascus pigment as inner water phase, flaxseed gum (FG) as internal water phase gel, soybean oil as oil phase, and pea protein isolate (PPI) as outer water phase. We aimed to investigate the quality of pork emulsion systems in which pork fat was replaced by W/O/W emulsions. The results revealed that addition of W/O/W emulsions reduced lipid contents from 11.22% to 5.09%, enhanced protein level from 15.77% to 17.02%, increased polyunsaturated fatty acid composition from 23.36% to 59.63%, improved water-holding capacity and oxidative stability compared to the control samples with pork fat. It was demonstrated that meat systems could achieve dual functions including decreasing the total fat content without affecting the hardness of the meat systems and color retention.

Formulation and characterization of W/O/W crystallizable double emulsions stabilized by OSA starch/xanthan gum mixture as drug delivery systems

Water-in-oil-in-water (W/O/W) crystallizable double emulsions stabilized with a mixture of octenyl succinic anhydride starch (OSA starch) and xanthan gum (XG) were formulated. These systems were proposed as modules for the release of chlortetracycline (CTC). The characterization results indicated that the stability, the average diameter of the globules, and the apparent viscosity of the double emulsions formulated depend on OSA starch and XG concentrations, and on their ratio in the outer water phase. In addition, emulsions exhibited good creaming stability during 40 days of rest at 25 °C and 40 °C. However, samples prepared with 0.25%/0.5% and 0.5%/0.5% of OSA starch/XG mixture were found more stable. Also, it was noticed that the encapsulation efficiency (EE) and the release rate of CTC incorporated in the inner water phase strongly depend on the polymer concentrations in the outer water phase. Furthermore, the increase in the concentration of biopolymer results in a slowing down of the drug encapsulation and an improvement in the EE. Moreover, the Korsmeyer-Peppas model was tested to represent the kinetics of CTC release; the release mechanism was found as a simple diffusion type.

Multiple Pickering emulsions stabilized by the same particles with different extent of hydrophobization in situ.

Multiple emulsions are widely used in pharmaceuticals, foods, and cosmetics. However, those stabilized by surfactants with different HLB values are generally unstable due to the diffusion of the surfactants between inner and outer interfaces. Here, we report that multiple W/O/W emulsions can be prepared by using the same particles in combination with a surfactant of different concentrations. The less surface-active raw CaCO3 nanoparticles can be hydrophobized to surface-active in situ by adsorption of the anionic surfactant SDS, and the wettability of the particles can be controlled to be suitable for stabilizing both O/W and W/O Pickering emulsions by adjusting the surfactant concentration. With toluene as oil phase, the CaCO3 particles at 1.0 wt% tend to stabilize a W/O emulsion in the presence of 3 mm SDS in an aqueous solution, which can then be further dispersed in an aqueous phase with 1.0 wt% CaCO3 and SDS below 1 mm to form a W/O/W multiple emulsion. The effects of the ratio of W/O emulsion to the outer water phase and the preparation methods on stabilization of multiple emulsions were examined. With a ratio smaller than 3:1 and by gentle magnetic stirring, the multiple emulsions obtained can stay stable for at least a month without coalescence. This simple method not only ensures stabilization of multiple emulsions but also avoids complicated synthesis of colloid particles with different wettability.

Preparation and characterization of W1 /O/W2 emulsions stabilized by glycated and heat-modified egg white proteins.

Water-in-oil-in-water (W1 /O/W2 ) emulsions stabilized by protein-carbohydrate complexes were prepared from an inner water phase (W1 ), an oil phase (O) and an outer water phase (W2 ). The complexes consisted of heat-induced aggregates (HIAs) of isomalto-oligosaccharide/egg white protein Maillard conjugates. The effects of polyglycerol ester of polyricinoleic acid (PGPR) concentration, HIA concentration, W1 -to-O volume ratio and W1 /O-to-W2 volume ratio on the properties of the W1 /O/W2 emulsions were systematically investigated. At sufficiently high PGPR concentrations (>2%), the emulsions possess a high negative charge (≈-44 mV). The encapsulation efficiency of the emulsions, which was determined by incorporating a hydrophilic yellow dye in the inner water phase prior to homogenization, was relatively high (up to 93%) and did not change significantly during 14-day storage at 4°C. All emulsions were fluids that exhibited shear thinning behavior. Overall, this study shows that nature-derived emulsifiers can be used to create W1 /O/W2 emulsions suitable for application in the food industry. In addition, we provided a viable strategy to encapsulate water-soluble nutrients. © 2022 Society of Chemical Industry.

Development of Antimicrobial Edible Film Enriched with Double Emulsion of Cinnamon (Cinnamomum burmannii) Essential Oil

The edible film can be used as a carrier of bioactive compounds that contributed to the shelf life or nutritional benefit of food products; however, the addition of bioactive compounds relied greatly on the compatibility of the bioactive compound toward the edible film matrix. Most of the bioactive compounds are nonpolar which incompatible with the polar nature of the edible film. In this research, the nonpolar essential oil of cinnamon, a potent antimicrobial agent, was made into a double emulsion. The double emulsions were made through a two steps emulsification stages, with CaCl2 as the inner water phase and guar gum as the outer water phase. The physicochemical characteristics (stability, viscosity, and droplet size) and the antimicrobial activity of the double emulsion were observed. The double emulsion showed stability up to 7 days of storage at room temperature with high antimicrobial activity; MBC values of 0.86, 1.37, 0.31, and 0.51 mg/mL against E. coli , S. aureus , R. stolonifera , and A. niger , respectively. Different concentrations (5%,10%,15%) of both emulsions were added into edible film suspension. The formation of double emulsion showed a promising result as a means to incorporate nonpolar compounds into basic edible film formulation to increase its functional properties while retaining their physicochemical characteristic. All formulations showed good edible film characteristics, with edible film with 8% essential oil showing a high inhibition zone (15.81 dan 6.92 mm) toward E. Coli and R. stolonifer , 0.0052 mm thickness, the tensile strength of 6.32 MPa, 13% elongation and WVTR of 1.06 g/cm 2 .h.

Method for loading liposomes with soybean protein isolate hydrolysate influences the antioxidant efficiency of liposomal systems: Adding after liposomes formation or before lipid film hydration

This research investigated the method for loading liposomes with soybean protein isolate hydrolysate (SPIH) to create stable and antioxidative protein hydrolysate-containing liposomes. SPIH (SPIH-AF) prepared via a two-step hydrolysis by alcalase and flavourzyme was added at different concentrations to liposomes by two methods. More effective adsorption of SPIH-AF onto liposomal membrane occurred when it was added at 0.5 mg/mL and distributed in both the inner and outer water phases (addition before lipid film hydration), or added at lower concentrations (< 0.192 mg/mL) and distributed in the outer water phase (addition after liposomes formation). SPIH-AF concentration and distribution directly influenced its early rate of inhibition on lipid oxidation and membrane properties. SPIH-AF in the outer water phase functioned more effectively to inhibit lipid oxidation products accumulation. The interactions between SPIH-AF and liposomes altered SPIH-AF's secondary structures. Compared with Trp-liposomes interactions, Tyr-liposomes interactions were more sensitive to SPIH-AF concentration and distribution. SPIH-AF distribution affected strongly the electrostatic interactions (but weakly the hydrophobic interactions). Tyr/Trp-liposomes interactions were more powerful when SPIH-AF was located in both the inner and outer water phases at higher concentrations.

Development of Lipid-Based Gastroretentive Delivery System for Gentian Extract by Double Emulsion-Melt Dispersion Technique.

Gentian (Gentiana lutea L., Gentianaceae) root extract (GRE) is used for the treatment of gastrointestinal disorders. However, its bioactive potential is limited in conventional forms due to the low bioavailability and short elimination half-life of the dominant bioactive compound, gentiopicroside. The aim of study was to encapsulate GRE in the lipid-based gastroretentive delivery system that could provide high yield and encapsulation efficiency, as well as the biphasic release of gentiopicroside from the tablets obtained by direct compression. Solid lipid microparticles (SLM) loaded with GRE were prepared by freeze-drying double (W/O/W) emulsions, which were obtained by a multiple emulsion–melt dispersion technique, with GRE as the inner water phase, Gelucire® 39/01 or 43/01, as lipid components, with or without the addition of porous silica (Sylysia® 350) in the outer water phase. Formulated SLM powders were examined by SEM and mercury intrusion porosimetry, as well as by determination of yield, encapsulation efficiency, and flow properties. Furthermore, in vitro dissolution of gentiopicroside, the size of the dispersed systems, mechanical properties, and mucoadhesion of tablets obtained by direct compression were investigated. The results have revealed that SLM with the macroporous structure were formulated, and, consequently, the powders floated immediately in the acidic medium. Formulation with porous silica (Sylysia® 350) and Gelucire® 43/01 as a solid lipid was characterized with the high yield end encapsulation efficiency. Furthermore, the mucoadhesive properties of tablets obtained by direct compression of that formulation, as well as the biphasic release of gentiopicroside, presence of nanoassociates in dissolution medium, and optimal mechanical properties indicated that a promising lipid-based gastroretentive system for GRE was developed.

Co-delivery of insulin and quercetin in W/O/W double emulsions stabilized by different hydrophilic emulsifiers

Insulin (hydrophilic) and quercetin (hydrophobic) have broad biological benefits; however, their rapid hydrolysis (via protease degradation) during digestion hinders their stability and delivery for absorption before degrading. In this study, we encapsulated insulin and quercetin using a self-assembled water-in-oil-in-water (W/O/W) double emulsion. We prepared the co-delivery emulsion by two-step emulsification and investigated the effects of the type of hydrophilic emulsifier for the outer water phase on the physicochemical properties, stability, and digestive properties. The black-bean-protein-stabilized W/O/W double emulsion had a higher absolute zeta potential value (52.80 mV), higher encapsulation efficiency (insulin: 95.7%, quercetin: 93.4%), lower viscosity, better emulsifying properties (EAI: 122.26 m2/g, ESI: 224 min), and lower levels of hydroperoxides (0.86 mmol/L) and TBARS (25.80 μmol/L) than emulsions stabilized by other hydrophilic emulsifiers. The emulsion yielded a 2.60- and 4.56-fold increase in the bioaccessibility of insulin and quercetin, respectively, while increasing their chemical stability and solubility under simulated gastrointestinal conditions.

Optimized Taste-Masked Microparticles for Orally Disintegrating Tablets as a Promising Dosage Form for Alzheimer's Disease Patients.

The objective of this research was to optimize the tasted-masked microparticles for orally disintegrating tablets containing donepezil hydrochloride using quality risk assessment and design of experiment approaches. The double emulsion solvent evaporation technique using aminoalkyl methacrylate copolymer (AMC) was used to prepare taste-masked microparticles. Factors affecting the quality of the taste-masked microparticles were analyzed using an Ishikawa diagram. A risk-ranking approach was used to rank the formulation and process risks. Furthermore, the effect of AMC quantity, stirring time, and volume of outer water phase on various responses, such as particle size, the amount of drug dissolved at 5 min (Q5) in simulated saliva fluid, and mean dissolution time (MDT) in simulated gastric fluid, was investigated using the Box-Behnken design. The optimized microparticles were then used to prepare orally disintegrating tablets (ODTs) and evaluated by in vitro and in vivo testing. The results demonstrated that particle size was influenced by the AMC amount and stirring time. Q5 was significantly affected by the amount of AMC and the volume of the outer water phase. On the other hand, these two factors had a positive effect on MDT. The optimized microparticles had a particle size of 174.45 ± 18.19 µm, Q5 of 5.04%, and MDT of 5.97 min. The ODTs with taste-masked microparticles showed acceptable in vitro dissolution with an MDT of 5 min. According to the results of a panel of six human volunteers, they greatly improved palatability.

W/O/W double emulsion-loaded alginate capsules containing Lactobacillus plantarum and lipophilic sea buckthorn (Hippophae rhamnoides L.) pomace extract in different phases.

In this study, double emulsion containing L. plantarum F1 cells and prebiotic mannitol in the inner water phase, lipophilic sea buckthorn pomace extract as an antioxidant in the oil phase, and alginate in the outer water phase showed high encapsulation yield (82.19%), good cell survival rate (76.99%) and low chemical degradation of the oil (peroxide value - 3.8 meq O2/kg fat) after 42 days of storage. Gelation of the outer water phase enhanced the viability of L. plantarum F1 cells both during storage and under gastrointestinal conditions due to strong physical barrier formation. Encapsulated L. plantarum F1 viability throughout the 30-day storage period decreased to the value meeting the minimum required dose for probiotics. In vitro digestion of the loaded alginate capsules showed high survival rate of encapsulated cells under gastric conditions and significant reduction at the end of the duodenal phase of digestion.

Preparation of Snake Neurotoxin Nanocapsules and the Analgesic Mechanism of P38 Mitogen-Activated Protein Kinase Signal Pathway Combining Snake Neurotoxin Nanocapsules with Gabapentin

This study aimed to explore the analgesic effect of snake neurotoxin combined with gabapentin (Gab) on neuropathic pain in rats with chronic compression injury (CCI) of the sciatic nerve based on the nanotechnology. Firstly, various solutions were prepared to obtain the inner water phase, the oil phase, the outer water phase, and the dilution phase. Poly(lactic-co-glycolic) Acid (PLGA) and polyethylene glycol-poly(lactic-co-glycolic) acid (PEG-PLGA) were added to the prepared oil phase solution to obtain the PLGA snake neurotoxin nanocapsule and PEG-PLGA snake neurotoxin nanocapsule, respectively. After the nanocapsules were obtained, a rat CCI model was further modelled, and the reactive oxygen species (ROS) content in the rat brain tissue was analyzed and tested by the kit, and the optimal physical conditions for preparing the nanocapsules were tested. In order to test the effect of nanocapsules on the p38 mitogen-activated protein kinase (MAPK) signaling pathway, the rats were divided into Control group, Sham group, CCI group, Gabapentin (Gab) group, and PEG-PLGA snake neurotoxin nanocapsule + Gab group. The rats in different groups were given abdominal injections to compare relevant indicators of signal pathway. In the experiment, neuropathic pain was related to changes in ROS content, and snake neurotoxin nanocapsules could reduce the ROS content; PLGA snake neurotoxin nanocapsules and PEG-PLGA snake neurotoxin nanocapsules had encapsulation efficiencys of 24.7% and 22.8% and drug loading of 3.28% and 3.02%, respectively, and the particle sizes of prepared nanocapsules were 760 nm~1,150 nm. Besides, the phase transition temperature of about 50 °C and the light time of 1 h can accelerate the release of nanocapsules to the greatest extent; and the snake neurotoxin could inhibit the activation of p38 MAPK signaling pathway so as to play the analgesic effects on neuropathic pain.