A rheological and microstructural characterisation of bigels for cosmetic and pharmaceutical uses

Development and characterization of hydrogel-in-oleogel (bigel) systems and their application as a butter replacer for bread making

BACKGROUND

Butter has been widely used in bakery products and it contains high level of saturated fats. However, excessive consumption of saturated fats would increase the risk of chronic disease. This study was to fabricate water-in-oil (W/O) type bigels as butter replacers to improve the quality attributes of breads.

RESULTS

A stable water-in-oil (W/O) type bigel system was fabricated based on mixed oleogelators (rice bran wax and glycerol monostearate) and sodium alginate hydrogel. The ratios of oleogel to hydrogel could significantly affect the stability, microstructure and rheological properties of bigels. All of the bigels exhibited solid-like properties, with increased oleogel fractions, and the network structure of bigel became more compact and orderly with smaller sodium alginate gel particles. Meanwhile, the viscoelastic modulus and firmness of bigel increased, contributing to a higher stability. The bigel dough exhibited lower gel strength and relatively higher extensibility compared to the butter dough. Regardless of oleogel fractions, all the bigel produced bread with a higher specific volume and softer texture than the butter bread. When the oleogel fractions was less than 80%, increasing the oleogel fractions was more beneficial for improving the specific volume, softness and fluffy structure of bread.

CONCLUSION

W/O type bigel as butter replacers showed great potential in improving the appearance, structure and textural properties of bread. © 2023 Society of Chemical Industry.

Lecithin Organogel: A Promising Carrier for the Treatment of Skin Diseases

Skin is the largest organ of the human body, as it protects the body from the external environment. Nowadays, skin diseases and skin problems are more common, and millions of people are affected daily. Skin diseases are due to numerous infectious pathogens or inflammatory conditions. The increasing demand for theoretical research and practical applications has led to the rising prominence of gel as a semisolid material. To this end, organogels has been widely explored due to their unique composition, which includes organic solvents and mineral or vegetable oils, among others. Organogels can be described as semisolid systems wherein an organic liquid phase is confined within a three-dimensional framework consisting of self-assembled, cross-linked, or entangled gelator fibers. These gels have the ability to undergo significant expansion and retain substantial amounts of the liquid phase, reaching up to 99% swelling capacity. Furthermore, they respond to a range of physical and chemical stimuli, including temperature, light, pH, and mechanical deformation. Notably, due to their distinctive properties, they have aroused significant interest in a variety of practical applications. Organogels favor the significant encapsulation and enhanced permeation of hydrophobic molecules when compared with hydrogels. Accordingly, organogels are characterized into lecithin organogels, pluronic lecithin organogels, sorbitan monostearate-based organogels, and eudragit organogels, among others, based on the nature of their network and the solvent system. Lecithin organogels contain lecithin (natural and safe as a living cell component) as an organogelator. It acts as a good penetration enhancer. In this review, first we have summarized the fundamental concepts related to the elemental structure of organogels, including their various forms, distinctive features, methods of manufacture, and diverse applications. Nonetheless, this review also sheds light on the delivery of therapeutic molecules entrapped in the lecithin organogel system into deep tissue for the management of skin diseases and provides a synopsis of their clinical applications.

Novel bigels based on walnut oil oleogel and chitosan hydrogel: Preparation, characterization, and application as food spread

This study developed new biphasic gel systems containing a walnut oil-based oleogel and a chitosan hydrogel and evaluated the application on food spread. The effects of different oleogelators [γ-oryzanol/β-sitosterol (γ-ORY/β-SIT), candelilla wax/span 65 (CW/SA), and mono- and diglycerides of fatty acids] were explored. Rheological analysis showed that γ-ORY/β-SIT-based bigel had the strongest gel strength, but XRD confirmed that β' crystal form (d = 3.72 Å, 4.12 Å) was predominantly in the CW/SA-based bigel, which was more appropriate for application as spread. The characteristics of CW/SA-based bigel with different oleogel fractions (40-80 wt%) were investigated. The microscopic images indicated that the hydrogels were dispersed as small droplets in the oleogels after oleogel fraction reaching 60 %. The highest crystallinity was achieved when the oleogel fraction was 60 %, and its oil binding capacity was 96.49 %. Textural analysis showed that the CW/SA-based bigel (OG-60 %) had similar properties with commercial spread B, and can be used as a partial replacement for spread B. Replacing 75 % of the commercial spread B with the bigel was found to be optimal and displayed acceptable sensory features. This study developed a healthy bigel based on walnut oil and provided the in-depth information for bigels as an alternative to plastic fats.

Tailoring the oral sensation and digestive behavior of konjac glucomannan-gelatin binary hydrogel based bigel: Effects of composition and ratio

In the food industry, there is a growing demand for bigels that offer both adaptable oral sensations and versatile delivery properties. Herein, we developed bigels using a binary hydrogel of konjac glucomannan (KGM) and gelatin (G) combined with a stearic acid oleogel. We closely examined how the oleogel/hydrogel volume ratio (φ) and the KGM/G mass ratio (γ) influenced various characteristics of the bigels, including their microstructure, texture, rheological properties, thermal-sensitivity, oral tribology, digestive stability, and nutraceutical delivery efficiency. A noteworthy observation was the structural evolution of the bigels with increasing φ values: transitioning from oleogel-in-hydrogel to a bicontinuous structure, and eventually to hydrogel-in-oleogel. Lower γ values yielded a softer, thermally-responsive bigel, whereas higher γ values imparted enhanced viscosity, stickiness, and spreadability to the bigel. Oral tribology assessments demonstrated that φ primarily influenced the friction sensations at lower chewing intensities. In contrast, γ played a significant role in augmenting oral friction perceptions during more intense chewing. Additionally, φ dictated the controlled release and bioaccessibility of curcumin, while γ determined digestive stability. This study provides valuable insights, emphasizing that through meticulous selection and adjustment of the hydrogel matrix composition, bigels can be custom-fabricated to achieve specific oral sensations and regulated digestive behaviors.

Effect of the gelling mechanism on the physical properties of bigels based on whey protein isolate

The effect of the cold-set and heat-set gelling mechanism of whey protein isolate on bigel production was assessed. For this purpose, hydrogel phase was produced with whey protein isolated (10 % w/v) and for oleogel sunflower oil and glycerol monostearate (7.5 % w/v) were used. Bigels were produced by hot emulsification of different hydrogel:oleogel ratios (from 90:10 up to 10:90). For cold-set bigels (CSB) NaCl (200 mM) was added to the aqueous phase prior to the emulsification and the emulsion was cooled to promote the 3D network formation. On the other hand, heat-set bigels (HSB) were produced by heating the emulsion (80 °C, 60 min). Bigels were evaluated through microscopy, FTIR, thermal and texture analyzes. Results showed that depending on the hydrogel:oleogel ratio and gelling mechanism different structures organization were obtained. CSB were more organized, showing that the rate of gelation was the mechanism responsible for the structure. However, for HSB the heat treatment destabilized the emulsion and disorganized structures were observed for high oleogel content. FTIR corroborates the visual observation and showed that the arrangement was purely physical. In addition, the structural arrangement led to different mechanical properties. In general, HSB produced gels with rubber-like behavior, higher elasticity modulus and the presence of a breaking point. In contrast, CSB behaves as squeezing gel, with no breaking point and lower values of elasticity modulus. Moreover, for O/W bigels the dispersed oleogel particles disrupted the WPI network decreasing the gel strength in comparison to pure hydrogels. However, for systems where oleogel was the continuous phase, the gel strength was recovered due to the metastable and dynamic character of these systems. Thus, results showed that the gelling mechanism of the protein exerted an effect on the physical properties of bigels. In addition, the mechanical properties also can be modulated according to the bigel composition, allowing its application in products with different sensorial characteristics.

Flexible control of bigel microstructure for enhanced stability and flavor release during oral consumption

Edible delivery systems such as emulsions and gels that possess flexible oral flavor sensation and comprehensive stability under freeze-thaw processing are highly demanded in the frozen food industry. Bigels were fabricated via emulsification of stearic acid based oleogel with konjac glucomannan (KGM)-gelatin (G) based binary hydrogel. By varing the KGM/G mass ratio (γ) and oleogel/hydrogel volume ratio (φ) of bigels, modulation over the micromorphology, tribology, flavor sensation and cheese stick imitating capacity were achieved. Notably, as φ increased from O4:W6 to O5:W5, the microstructural transformation from oleogel-in-hydrogel to bicontinuous morphology emerged as a remarkable feature. The influence of γ was evident in bicontinuous bigels, significantly enhancing water holding capacity (WHC) by 3.38-fold as γ transitioned from 1KGM:5G to 6KGM:5G during freeze-thaw cycles. φ and γ both played pivotal roles in altering the microstructure and rheological properties of the bigels, enabling customizable release of bioactive components and flavor perception. Oleogel-in-hydrogel bigels effectively prevented bioactive compound leakage during freeze-thaw conditions, while bicontinuous bigels demonstrated sustained flavor release during oral mastication. Release behaviors were dual-controlled by φ and γ, reducing oil-soluble flavor release with increased φ and lowering hydrophilic volatile release with elevated γ. Moreover, bigel-based cheese sticks showcased lower viscosity, higher creep recovery rates, and enhanced mouthfeel during minimal oral chewing, suggesting their potential in mimicking the properties of commercial counterparts. These findings extend insights into bigel design for tailored flavor release and bioactive preservation in food products.

Evaluation of the in vitro performance of generic and original adapalene gel

OBJECTIVE

The aim was to evaluate the difference of the in vitro behavior between the commercially available generic adapalene gel and original product with Topical Classification System (TCS), and to analyze the effect of changes of excipients on the release behavior.

SIGNIFICANCE

Establishing in vitro performance assays to understand the impact of formulation variables on the critical quality attributes (CQA) is critical for the quality assessment of semi-solid generic drug.

METHODS

In vitro release (IVR), in vitro permeation (IVP), viscosity, and pH measurement methods for adapalene gels were established and validated. The differences between generic adapalene gel from 7 companies and original products were evaluated by correlation analysis (CA) and principal component analysis (PCA), and the relationship among 4 parameters was elucidated. The effect of excipients on the above variables was examined by univariate tests.

RESULTS

There were some differences between the gels of 5 of the 7 imitation enterprises and reference listed drug (RLD). There were varying degrees of correlation between viscosity, pH, the adapalene amount retained in skin and release rate. The result validated the key role of IVR, and identified that pH value, type of suspending agent, the amount of carbomer, etc. had certain effects on the release rate.

CONCLUSIONS

The factors mentioned above should be considered when developing and manufacturing generic adapalene gels, and the application of TCS in the evaluation of generic topical drugs was advanced. Additionally, our research revealed some discrepancies from USP<1724>, which could be valuable information for the revision.

Rheological and Viscoelastic Analysis of Hybrid Formulations for Topical Application

The rheological and viscoelastic properties of hybrid formulations composed of vehicles designed for cutaneous topical application and loaded with ultradeformable liposomes (UDL) were assessed. UDL were selected for their established ability to transport both lipophilic and hydrophilic compounds through the skin, and are applicable in pharmaceuticals and cosmetics. Formulations underwent flow analysis and were fitted to the Herschel-Bulkley model due to their prevalent non-Newtonian behavior in most cases. Linear viscoelastic regions (LVR) were identified, and G' and G″ moduli were determined via frequency sweep steps, considering the impact of temperature and aging. The formulations exhibited non-Newtonian behavior with pseudoplastic traits in most cases, with UDL incorporation inducing rheological changes. LVR and frequency sweep tests indicated predominantly elastic solid behavior, with G' higher than G″, at different temperatures and post-production times. Tan δ values also illustrated a predominant solid-like behavior over liquid. This study provides pivotal insights into the rheological and viscoelastic features of topical formulations, emphasizing the crucial role of meticulous vehicle and formulation selection when incorporating UDL or analogous liposomal drug delivery systems.

A biocompatible lipid-based bigel for topical applications

The development of biocompatible delivery systems is a necessity for medical and topical applications. Herein, the development of a new bigel for topical application is described. It is composed of 40% colloidal lipid hydrogel and 60% olive oil and beeswax oleogel. Its characterization and the potential of the bigel as a drug carrier through the skin was evaluated in vitro using fluorescence microscopy and two phases of the bigel were labeled with two fluorescent probes: sodium fluorescein (hydrophilic phase) and Nile red (lipophilic phase). The structure of the bigel showed two phases with fluorescence microscopy in which the hydrogel phase was incorporated into a continuous oleogel matrix. Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR) presented a combination of vibrations characteristic of the different molecules forming the bigel, and Differential Scanning Calorimetry (DSC) showed different transitions attributed to beeswax lipids. Small-angle and wide-angle X-ray scattering (SAXS and WAXS) indicated a predominant lamellar structure with orthorhombic lateral packing that could be related to the arrangement of beeswax crystals. Bigel enables deeper penetration of hydrophilic and lipophilic probes into deeper layers, making it a promising candidate for effective topical carriers in medical and dermatological applications.

Bigels as Delivery Systems: Potential Uses and Applicability in Food

Bigels have been mainly applied in the pharmaceutical sector for the controlled release of drugs or therapeutics. However, these systems, with their intricate structures, hold great promise for wider application in food products. Besides their classical role as carrier and target delivery vehicles for molecules of interest, bigels may also be valuable tools for building complex food structures. In the context of reducing or even eliminating undesirable (but often highly functional) food components, current strategies often critically affect food structure and palatability. The production of solid fat systems that are trans-fat-free and have high levels of unsaturated fatty acids is one of the challenges the food industry currently faces. According to recent studies, bigels can be successfully used as ingredients for total or partial solid fat replacement in complex food matrices. This review aims to critically assess current research on bigels in food and pharmaceutical applications, discuss the role of bigel composition and production parameters on the characteristics of bigels and further expand the use of bigels as solid fat replacers and functional food ingredients. The hydrogel:oleogel ratio, selected gelators, inclusion of surfactants and encapsulation of molecules of interest, and process parameters (e.g., temperature, shear rate) during bigel production play a crucial role in the bigel's rheological and textural properties, microstructure, release characteristics, biocompatibility, and stability. Besides exploring the role of these parameters in bigel production, future research directions for bigels in a food context are explored.

Fabrication and Characterization of Novel Food-Grade Bigels Based on Interfacial and Bulk Stabilization

Novel food-grade bigels were fabricated using zein nanoparticles for interfacial stabilization and non-surfactant gelators (beeswax and tapioca) for bulk stabilization. The present study demonstrated the importance of interfacial stability for biphasic gels and sheds light on the roles of the gelation mechanism and the oil/water ratio of a bigel on its microstructure, physical properties, and digestion behaviors. The results indicated that it is not an easy task to realize homogenization and subsequent gelation in beeswax-tapioca biphasic systems, as no amphiphilic components existed. However, applying the binding of zein nanoparticles at the oil-water interface allowed us to produce a homogeneous and stable bigel (oil fraction reach 40%), which exhibited enhanced structural and functional properties. Oleogel structures play a crucial role in determining the deformation response of bigel systems. As the oil content increased, the mechanical strength and elastic properties of bigels were enhanced. In the meantime, clear bigel-type transitions were observed. In addition, the fabricated bigels were shown to be beneficial for delayed digestion, and the lowest degree of lipolysis could be found in bigel with 50% oleogel.

Bigel formulations based on sesame oleogel with probiotics alginate hydrogel: A novel structure for nutritious spreadable butter

As a replacement for saturated fats, bigel butter spread (BgBs) based on sesame oleogel and alginate hydrogel was developed. Morphology, oxidative stability, microbiological, chemical, and sensory analysis were assessed. The results demonstrated that unsaturated fatty acids were higher in cinnamon (73.87 %) than in plain (71.57 %) BgBs. The peroxide value was higher in plain (5.25 meqO₂/kg) than in cinnamon BgBs (4.29 meqO₂/kg). Cinnamon BgBs had 44.44 % more antioxidant activity compared to plain BgBs (40.20 %). Moreover, BgBs products kept their probiotic counts at >7 log cycles. The cinnamon BgBs had a lower microbial load than plain BgBs. The chemical composition of the BgBs products did not change significantly. But the pH values slightly dropped with the storage time. The sensory evaluation of plain and cinnamon BgBs did not significantly differ from one another. However, the period of storage and the addition of the cinnamon oil significantly affected the flavor ratings.

Optimization of folic acid Span 60-organogel to enhance its in vitro and in vivo photoprotection: a comparative study

Aim: The acute effects of UV sunlight exposure were inflammation, erythema, and swelling. The present work aims to formulate a novel organogel preparation that can achieve efficient topical folic acid (FA) delivery to cure inflammation from acute exposure to UV sunlight. Methods: The organogels were prepared by direct melting and stirring on a magnetic stirrer. Photostability and in vivo photoprotection were investigated. Results: Optimized organogel showed more sustained release, more photostability, more effective antioxidant activity, higher in vitro sun protection factor, and greater extent of skin photoprotection from natural sunlight. Conclusion: The present results suggest optimized FA organogel as a promising formulation for effective delivery of FA to the skin maximizing it's in vitro and in vivo performance.

Novel biphasic gels can mimic and replace animal fat in fully-cooked coarse-ground sausage

Four biphasic gels (BPG) were developed and tested as pork fat replacers in coarse-ground fully-cooked sausages. An oleogel (OG) phase (92.5% high-oleic soybean oil, 7.5% rice bran wax) and one of two hydrogel (HG) phases (water and 7% or 8% gelatin) were combined in 7:3 or 6:4 OG:HG ratios, for a total of four test formulations. Control sausages were formulated to 27.5% fat and stored at 0-2 °C for 98 d. BPGs allowed for fat reductions of up to 26%. Visually, all BPGs resembled pork fat. There were no differences in external L* and a* but, internally, controls were darker and redder. Except for one control, there were no differences in Texture Profile Analysis (TPA) hardness, cohesiveness, springiness, and chewiness. Warner-Bratzler Shear (WBS) force was highest in 6:4 samples, which were also highest in Sensory First Bite Firmness and lowest in Smoked Sausage Aroma and Smoked Sausage Flavor. TBARS values remained steady, with no rancid flavors detected by the sensory panel.

Bijels as a Fluid Labyrinth for Drugs: The Effect of Nanoparticles on the Release Kinetics of Ethosuximide and Dimethyl Fumarate

Bijels (bicontinuous interfacially jammed emulsion gels) raised an increasing interest as biomaterials for controlled drug delivery due to their biphasic nature organized in mesoscopic tortuous domains. Two bijel formulations were prepared and explored as delivery systems for both hydrophilic and lipophilic drugs, ethosuximide and dimethyl fumarate. The two bijel-like structures, based on polymerized ε-caprolactone/water, differ in the stabilizing nanoparticle hydroxyapatite (inorganic) and nanogel-based nanoparticles (organic). Diffusion nuclear magnetic resonance spectroscopy has been used to characterize the bijel structure and the transport behavior of the drug molecules confined within the water/organic interconnected domains. A reduced diffusion coefficient is observed for several concentrations of the drugs and both bijel formulations. Moreover, in vitro release profiles also reveal the effect of the microstructure and drug-nanoparticle interactions.

Effect of Potato Starch Hydrogel:Glycerol Monostearate Oleogel Ratio on the Physico-Rheological Properties of Bigels

Bigel (BG) has been shown to be promising for the food industry due to the possibility to manipulate the properties of the system by adjusting the ratio of each individual phase, namely the hydrogel (H) and oleogel (O) phases. This work aimed to evaluate the influence of the O:H ratio on the physical-rheological properties of BG produced with potato starch (PS) and glycerol monostearate (GM). The hydrogel hardness (i.e., 1423.47 g) directly influenced the viscosity of the BG samples, as BG with a higher H-phase presented the highest viscosity and firmness. All BG samples presented shear-thinning behavior and structural breakdown at ~50 °C. BG with a higher O-phase had superior results for thermal stability, softer texture, and yield stress values, representative of good plasticity and spreadability, as compared to BG with less O-phase. The BG with 80% H-phase was less stable during the 21 days of storage in relation to the other BG samples. This study showed the role that the O:H ratio plays in the development of PS-GM-based BGs with tailor-made physical-rheological properties. In addition, the BG is an easily reproduced system with great potential to be used as a trans and saturated fat substitute in food applications.

Fabrication of chitosan-cinnamaldehyde-glycerol monolaurate bigels with dual gelling effects and application as cream analogs

In this study, chitosan-based bigels were fabricated, where glycerol monolaurate was added in MCT oil to produce a gelled lipid phase and cinnamaldehyde was included in the lipid phase in order to act as a crosslinking agent. The synergistic effect of pH on chemical crosslinking effects was investigated. The potential of using these bigels as an alternative to cream was also investigated. The pH of the aqueous phase played an important role in controlling the extent of the Schiff-base reaction promoted by cinnamaldehyde. At pH 3.8, the bigels formed were homogenous but at pH 5.0 and 5.5 they exhibited phase separation, which highlighted the importance of chemical crosslinking. To better mimic the properties of real cream, span 80 was added to create a more homogeneous and smoother structure of the bigels. These bigels might provide a healthy and more sustainable alterative to food products that contain plastic fats, like cream.

Influence of Anaerobic Degradation of Organic Matter on the Rheological Properties of Cohesive Mud from Different European Ports

The presence of clay-organic flocs in cohesive mud results in a complex rheological behavior of mud, including viscoelasticity, shear-thinning, thixotropy and two-step yielding. In this study, the effect of microbial degradation of organic matter on the rheological properties of mud samples, collected from different ports, was examined. The mud samples were collected from five different European ports (Port of Antwerp (PoA), Port of Bremerhaven (PoB), Port of Emden (PoE), Port of Hamburg (PoH) and Port of Rotterdam (PoR)), displaying varying sediment properties. The rheological analysis of fresh and degraded mud samples was performed with the help of several tests, including stress ramp-up tests, amplitude sweep tests, frequency sweep tests, time-dependent tests and structural recovery tests. The results showed: (i) a significant decrease in yield stresses and complex modulus after organic matter degradation for mud samples from PoA, PoH and PoR, (ii) a negligible change in rheological properties (yield stresses, crossover amplitude and complex modulus) for mud samples from PoB, and (iii) a significant increase in rheological properties for mud samples from PoE. For time-dependent tests, mud samples from PoB showed a substantial increase in hysteresis (~50% mean value) as compared to the changes in yield stresses and crossover amplitude. The analysis of gas production during degradation of organic matter showed a (i) significant release of carbon per g dry matter for mud samples from PoA, PoH and PoR, (ii) lower carbon release per g dry matter for mud samples from PoB, and (iii) a negligible carbon release per g dry matter for mud samples from PoE, which corresponded well with the change in rheological properties.

Multicompartment Hydrogels

Hydrogels belong to the most promising materials in polymer and materials science at the moment. As they feature soft and tissue-like character as well as high water-content, a broad range of applications are addressed with hydrogels, e.g. tissue engineering and wound dressings but also soft robotics, drug delivery, actuators and catalysis. Ways to tailor hydrogel properties are crosslinking mechanism, hydrogel shape and reinforcement, but new features can be introduced by variation of hydrogel composition as well, e.g. via monomer choice, functionalization or compartmentalization. Especially, multicompartment hydrogels drive progress towards complex and highly functional soft materials. In the present review the latest developments in multicompartment hydrogels are highlighted with a focus on three types of compartments, i.e. micellar/vesicular, droplets or multi-layers including various sub-categories. Furthermore, several morphologies of compartmentalized hydrogels and applications of multicompartment hydrogels will be discussed as well. Finally, an outlook towards future developments of the field will be given. The further development of multicompartment hydrogels is highly relevant for a broad range of applications and will have a significant impact on biomedicine and organic devices. This article is protected by copyright. All rights reserved.

Influence of the Mixtures of Vegetable Oil and Vitamin E over the Microstructure and Rheology of Organogels

Candelilla wax (CW) and 12-hydroxystearic acid (12HSA) are classic solid-fiber-matrix organogelators. Despite the high number of studies using those ingredients in oily systems, there is scarce literature using a mixture of oil and antioxidants. Vitamin E (VE) is an important candidate for its lipophilicity and several applications on pharmaceutical, cosmetics, and food industries. In this work, we investigated the influences of mixtures between vegetable oil (VO) and VE on the microstructures and rheological properties of CW and 12HSA organogels. A weak gel (G′′/G′ > 0.1) with a shear-thinning behavior was observed for all samples. The presence of VE impacted the gel strength and the phase transition temperatures in a dose-dependent pattern. Larger and denser packed crystals were seen for 12HSA samples, while smaller and more dispersed structures were obtained for CW organogels. The results obtained in this work allowed the correlation of the structural and mechanical properties of the organogels, which plays an important role in the physical-chemical characteristics of these materials.

Bigels as drug delivery systems: From their components to their applications

Bigels are systems that usually result from mixing a hydrogel and an organogel: the aqueous phase is commonly formed by a hydrophilic biopolymer, whereas the organic phase comprises a gelled vegetable oil because of the presence of an organogelator. The proportion of the corresponding gelling agent in each phase, the organogel/hydrogel ratio, and the mixing temperature and speed all need to be taken into consideration for bigel manufacturing. Bigels, which are particularly useful drug delivery systems, have already been formulated for transdermal, buccal, and vaginal routes. Mechanical assessments and microscopy are the most reported characterization techniques. As we review here, their composition and unique structure confer promising drug delivery attributes, such as mucoadhesion, the ability to control drug release, and the possibility of including both hydrophilic and lipophilic drugs in the same system.

Carbopol-olive oil-based bigel drug delivery system of doxycycline hyclate for the treatment of acne

OBJECTIVE

The objective of this study was to prepare and evaluate the doxycycline hyclate containing bigel for the effective treatment of acne.

METHODS

Bigels are biphasic systems formed by water-based hydrogels and oil-based organogel. Carbopol 940 was used to prepare the hydrogel phase, whereas Span-60 and olive oil for the oleogel phase.

RESULTS

The microstructure of bigel confirmed the oil in water type emulsion formation. The average droplet size of formulations was found 15-50 µm, and a bell-shaped droplet distribution curve, rheological, or viscosity studies suggested that the consistency and stability of bigel decrease with high organogel concentration. Three formulations (F1, F2, and F3) of the different ratios of hydrogel:oleogel (60:40, 70:30, and 80:20) were prepared in which F1 was less stable compared to F2 and F3. The drug content of F2 and F3 was respectively 79.94 and 71.33%. Formulation F2 was found more effective as compared to F3 based on in vitro drug release studies. Bigel also showed better results during in vivo studies at the rabbit ear model, which reduce acne diameter up to 1.10 mm from 4.9 mm while gel reduced it up to 1.20 mm.

Oleogel-Based Systems for the Delivery of Bioactive Compounds in Foods

Oleogels are semi-solid materials containing a large fraction of liquid oil entrapped in a network of structuring molecules. In the food industry, these formulations can be used to mimic fats and to deliver bioactive compounds. In the last decade, there has been increasing interest in these structures, not only from a scientific point of view, i.e., studying new molecules, methodologies for gelification, and new structures, but also from a technological point of view, with researchers and companies exploring these structures as a way to overcome certain challenges and/or create new and innovative products. One of the exciting applications of oleogels is the delivery of functional molecules, where the incorporation of oil-soluble functional compounds can be explored not only at the macroscale but also at micro- and nanoscales, resulting in different release behaviors and also different applications. This review presents and discusses the most recent works on the development, production, characterization, and applications of oleogels and other oleogel-based systems to deliver functional molecules in foods.

Development and characterization of novel bigels based on monoglyceride-beeswax oleogel and high acyl gellan gum hydrogel for lycopene delivery

The aim of present study was to develop novel bigels as a semi-solid vehicle for lycopene delivery. Bigels were prepared by using the mixture of glycerol monostearate (GMS)-beeswax based oleogel and high acyl gellan gum hydrogel in different proportions. The confocal microscopic observations showed that the obtained bigels were oleogel-in-hydrogel, and droplets became larger with increased contents of oleogel. Higher fractions of oleogel increased the mechanical strength (storage modulus, firmness) of bigels. According to the rheological results, all bigels exhibited solid-like characteristics since the storage modulus were larger than loss modulus. DSC results showed that the melting temperature of bigel was higher than that of oleogel. During in vitro simulated gastrointestinal digestion, the total release percentages varied from 60% to 80%, and a higher content of oleogel within bigels could slower down the release of lycopene, suggesting that a higher proportion of oleogel was beneficial for delivery of fat-soluble nutraceuticals.

Polymeric Gels and Their Application in the Treatment of Psoriasis Vulgaris: A Review

Psoriasis is a chronic skin disease, and it is especially characterized by the occurrence of red, itchy, and scaly eruptions on the skin. The quality of life of patients with psoriasis is decreased because this disease remains incurable, despite the rapid progress of therapeutic methods and the introduction of many innovative antipsoriatic drugs. Moreover, many patients with psoriasis are dissatisfied with their current treatment methods and the form with which the drug is applied. The patients complain about skin irritation, clothing stains, unpleasant smell, or excessive viscosity of the preparation. The causes of these issues should be linked with little effectiveness of the therapy caused by low permeation of the drug into the skin, as well as patients’ disobeying doctors’ recommendations, e.g., concerning regular application of the preparation. Both of these factors are closely related to the physicochemical form of the preparation and its rheological and mechanical properties. To improve the quality of patients’ lives, it is important to gain knowledge about the specific form of the drug and its effect on the safety and efficacy of a therapy as well as the patients’ comfort during application. Therefore, we present a literature review and a detailed analysis of the composition, rheological properties, and mechanical properties of polymeric gels as an alternative to viscous and greasy ointments. We discuss the following polymeric gels: hydrogels, oleogels, emulgels, and bigels. In our opinion, they have many characteristics (i.e., safety, effectiveness, desired durability, acceptance by patients), which can contribute to the development of an effective and, at the same time comfortable, method of local treatment of psoriasis for patients.

Vitamin E-loaded bigels and emulsions: Physicochemical characterization and potential biological application

Bigels have been studied as topical formulations for its benefits over sensory and drug delivery parameters. However, there is still few evidences about the properties of the combination of organogelators, oily phases and bioactive molecules into rheological and stability behavior. We investigated the use of classical organogelators (candelilla wax and 12-hydroxystearic acid) and oily phases (sunflower and mineral oil) in 5/95 organogel/polymeric hydrogel ratio to compare vitamin E bigels with its corresponding emulsions. The rheological measurements, microstructure, physical and oxidative stability properties and biological behavior were evaluated. The obtained oil-in-water bigels and emulsions showed crystallization pattern at the interface with high thermal and centrifuge-stress stability. Viscoelastic weak gels were obtained with higher thixotropy and consistency of 12-hydroxystearic bigels. The diameter of the inner phase was increased by vitamin E, despite its little influence over physical and oxidative stability of bigels and emulsions. Those findings indicated that sensory attributes may be regulated by the organogel composition.

The Effect of the HLB Value of Sucrose Ester on Physiochemical Properties of Bigel Systems

The current research explored the effect of different sucrose esters (SEs), with different hydrophilic–lipophilic balance (HLB) values, on bigel structure and properties. Bigels consisting of a water phase with glycerol and gelatin and an oil phase with glycerol mono-stearate, lecithin, and SEs with different HLB values were prepared. Rheological and thermal analyses revealed similar gelation-melting transitions governed by glycerol-monostearate crystallization (at ≈55 °C) for all bigel samples. The bigel matrix of the H1 and H2 samples (bigels consisting of SEs with HLBs of 1 and 2, respectively) demonstrated physical gel rheological characteristics of higher elastic and solid-like behavior compared with the H6 sample (bigel consisting SE with HLB 6). A similar trend was observed in the mechanical analysis with respect to hardness, firmness, and spreadability values, which were in the order of H1 > H2 > H6. This behavior was attributed to droplet size observed in the microscopy analysis, revealing significantly smaller droplets in the H1 and H2 samples compared with the H6 sample. These differences in droplet size were attributed to the diffusion kinetics of the low-molecular-weight surfactants. More specifically, the ability of mono-esterified SEs to diffuse faster than fully esterified SEs due to lower molar mass leads to a higher SE content at the oil-in-water (O/W) interface as opposed to the bulk oil phase. The results demonstrate the importance of the interface content in O/W bigel systems, providing an effective way to alter and control the bigel bulk properties.

Development of low-oil emulsion gel by solidifying oil droplets: Roles of internal beeswax concentration

There is increasing interest in the development of low-oil emulsion gels, but little is known about fabrication of low-oil emulsion gels by adjusting oil phase. Here, we reported a facile strategy to produce an ultrastable (at least 6 months) low-oil (25% oil) emulsion gels by solidifying the oil phase. The formation and stabilization mechanisms were explored. Beeswax (BW) encased liquid oil within the crystal network, forming solidified droplets. These solidified droplets promoted droplet-droplet interaction and tended to form network, further promoting gelling. Both linear and nonlinear rheology strongly supported the fact that BW enhanced the interaction of solidified droplets and strengthened the gel structure. Finally, we utilized low-oil emulsion gels as a delivery system of curcumin. The storage stabilities of curcumin at 4 and 20 °C were improved with 1, 3 and 5 wt% BW concentrations. This strategy greatly enriches emulsion gel formulations and their applications in foods.

An examination of carbopol hydrogel/organogel bigels of thymoquinone prepared by microwave irradiation method

Nigella sativa L. is shown wide spread over the world and contains many useful phytochemicals. Much of the biological activity of the seeds has been shown due to the presence of thymoquinone (TQ). Its poor aqueous solubility of TQ hinders its delivery to target site. The aim of this work was to prepare TQ bigels composed of Carbopol 974 P NF (C974) in PEG 400 (organogel) or C974 in water (hydrogel) with microwave heating method. A novel technique, high speed homogenization followed by microwave heating, was used to prepare organogels. The pH, electrical conductivity, differential scanning calorimetry, rheological properties, and morphological structure of the formulations have been evaluated, and the effect of microwave on drug content and TQ antioxidant activity has been investigated. The bigels of TQ were successfully produced via high-speed homogenization followed by microwave-assisted heating for the first time in this study. Highly lipophilic TQ was successfully dissolved in organogel, and it was not affected from the microwaves. It can be stated that microwave heating is a promising method to obtain C974 organogels and thus bigels with appropriate above indicated investigated physicochemical characteristics. The time and energy consumption could be decreased with microwave-assisted heating, especially for gel preparation in the field of pharmaceuticals.

Biopolymers for hydrogels in cosmetics: review

Hydrogels are cross-linked networks of macromolecular compounds characterized by high water absorption capacity. Such materials find a wide range of biomedical applications. Several polymeric hydrogels can also be used in cosmetics. Herein, the structure, properties and selected applications of hydrogels in cosmetics are discussed in general. Detailed examples from scientific literature are also shown. In this review paper, most common biopolymers used in cosmetics are presented in detail together with issues related to skin treatment and hair conditioning. Hydrogels based on collagen, chitosan, hyaluronic acid, and other polysaccharides have been characterized. New trends in the preparation of hydrogels based on biopolymer blends as well as bigels have been shown. Moreover, biopolymer hydrogels employment in encapsulation has been mentioned.