Gelatin-stabilised microemulsion-based organogels: rheology and application in iontophoretic transdermal drug delivery

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.

Hypothesizing the Oleic Acid-Mediated Enhanced and Sustained Transdermal Codelivery of Pregabalin and Diclofenac Adhesive Nanogel: A Proof of Concept

Pregabalin (PG) and diclofenac diethylamine (DEE) are anti-inflammatory molecules that are effective in relieving inflammation and pain associated with musculoskeletal disorders, arthritis, and post-traumatic pain, among others. Intravenous and oral delivery of these two molecules has their limitations. However, the transdermal route is believed to be an alternate viable option for the delivery of therapeutic molecules with desired physicochemical properties. To this end, it is vital to understand the physicochemical properties of these drugs, dosage, and strategies to enhance permeation, thereby surmounting the associated constraints and concurrently attaining a sustained release of these therapeutic molecules when administered in combination. The present work hypothesizes the enhanced permeation and sustained release of pregabalin and diclofenac diethylamine across the skin, entrapped in the adhesive nano-organogel formulation, including permeation enhancers. The solubility studies of pregabalin and diclofenac diethylamine in combination were performed in different permeation enhancers. Oleic acid was optimized as the best permeation enhancer based on in vitro studies. Pluronic organogel containing pregabalin and diclofenac diethylamine with oleic acid was fabricated. Duro-Tak® (87-2196) was added to the organogel formulation as a pressure-sensitive adhesive to sustain the release profile of these two therapeutic molecules. The adhesive organogel was characterized for particle size, scanning electron microscopy, and contact angle measurement. The HPLC method developed for the quantification of the dual drug showed a retention time of 3.84 minutes and 9.69 minutes for pregabalin and diclofenac, respectively. The fabricated nanogel adhesive formulation showed the desired results with particle size and contact angle of 282 ± 57 nm and ≥120⁰, respectively. In vitro studies showed the percentage cumulative release of 24.90 ± 4.65% and 33.29 ± 4.81% for pregabalin and diclofenac, respectively. In order to accomplish transdermal permeation, the suggested hypothesis of fabricating PG and DEE nano-organogel in combination with permeation enhancers will be a viable drug delivery method. In comparison to a traditional gel formulation, oleic acid as a permeation enhancer increased the penetration of both PG and DEE from the organogel formulation. Notably, the studies showed that the use of pressure-sensitive adhesives enabled the sustained release of both PG and DEE.Therefore, the results anticipated the hypothesis that the transdermal delivery of adhesive PG and DEEbased nanogel across the human skin can be achieved to inhibit inflammation and pain.

Organogels: "GelVolution" in Topical Drug Delivery - Present and Beyond

Topical drug delivery holds immense significance in dermatological treatments due to its non-invasive nature and direct application to the target site. Organogels, a promising class of topical drug delivery systems, have acquired substantial attention for enhancing drug delivery efficiency. This review article aims to explore the advantages of organogels, including enhanced drug solubility, controlled release, improved skin penetration, non-greasy formulations, and ease of application. The mechanism of organogel permeation into the skin is discussed, along with formulation strategies, which encompass the selection of gelling agents, cogelling agents, and additives while considering the influence of temperature and pH on gel formation. Various types of organogelators and organogels and their properties, such as viscoelasticity, non-birefringence, thermal stability, and optical clarity, are presented. Moreover, the biomedical applications of organogels in targeting skin cancer, anti-inflammatory drug delivery, and antifungal drug delivery are discussed. Characterization parameters, biocompatibility, safety considerations, and future directions in optimizing skin permeation, ensuring long-term stability, addressing regulatory challenges, and exploring potential combination therapies are thoroughly examined. Overall, this review highlights the immense potential of organogels in redefining topical drug delivery and their significant impact on the field of dermatological treatments, thus paving the way for exciting prospects in the domain.

Natural polysaccharide-based biodegradable polymeric platforms for transdermal drug delivery system: a critical analysis

Natural biodegradable polymers generally include polysaccharides (starch, alginate, chitin/chitosan, hyaluronic acid derivatives, etc.) and proteins (collagen, gelatin, fibrin, etc.). In transdermal drug delivery systems (TDDS), these polymers play a vital role in controlling the device's drug release. It is possible that natural polymers can be used for TDDS to attain predetermined drug delivery rates due to their physicochemical properties. These polymers can be employed to market products and scale production because they are readily available and inexpensive. As a result of these polymers, new pharmaceutical delivery systems can be developed that is both regulated and targeted. The focus of this article is the application of a biodegradable polymeric platform based on natural polymers for TDDS. Due to their biocompatibility and biodegradability, natural biodegradable polymers are frequently used in biomedical applications. Additionally, these natural biodegradable polymers are being studied for their characteristics and behaviors.

O/W microemulsion droplets diffuse through hydrogel network to achieve enhanced transdermal drug delivery

To overcome the poor water solubility of total flavones of Arisaematis rhizoma, microemulsions (MEs) can be used as a carrier for transdermal administration to promote their solubilization and skin permeability. Here, we investigated the physical compatibility of MEs in hydrogels and their skin permeation-enhancing effects. Transparency of microemulsion-based hydrogels (MBGs) was analyzed to evaluate ME compatibility with different hydrogel matrices. Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy were used to explore the microstructures of MBGs and ME–hydrogel combinations. Uniform and transparent MBG was obtained by adding 1% sodium hyaluronate (SH) to the optimized ME. MBG prepared with SH as a matrix expressed pseudoplastic-fluid and shear-thinning characteristics, making it easy to apply in clinical settings. No new FTIR peak occurred in the MBG compared with ME and hydrogel matrix, indicating a physical combination of ME and the polymer network gel. Nanoscale droplets of ME migrated in the gel network, and the migration capacity and in vitro transdermal permeation flux negatively correlated with SH concentration in the gel system. In conclusion, in MBGs, ME can keep nanoscale droplets migrating in the hydrogel network, thereby enhancing transdermal drug delivery.

Using Microemulsions: Formulation Based on Knowledge of Their Mesostructure

Microemulsions, as thermodynamically stable mixtures of oil, water, and surfactant, are known and have been studied for more than 70 years. However, even today there are still quite a number of unclear aspects, and more recent research work has modified and extended our picture. This review gives a short overview of how the understanding of microemulsions has developed, the current view on their properties and structural features, and in particular, how they are related to applications. We also discuss more recent developments regarding nonclassical microemulsions such as surfactant-free (ultraflexible) microemulsions or ones containing uncommon solvents or amphiphiles (like antagonistic salts). These new findings challenge to some extent our previous understanding of microemulsions, which therefore has to be extended to look at the different types of microemulsions in a unified way. In particular, the flexibility of the amphiphilic film is the key property to classify different microemulsion types and their properties in this review. Such a classification of microemulsions requires a thorough determination of their structural properties, and therefore, the experimental methods to determine microemulsion structure and dynamics are reviewed briefly, with a particular emphasis on recent developments in the field of direct imaging by means of electron microscopy. Based on this classification of microemulsions, we then discuss their applications, where the application demands have to be met by the properties of the microemulsion, which in turn are controlled by the flexibility of their amphiphilic interface. Another frequently important aspect for applications is the control of the rheological properties. Normally, microemulsions are low viscous and therefore enhancing viscosity has to be achieved by either having high concentrations (often not wished for) or additives, which do not significantly interfere with the microemulsion. Accordingly, this review gives a comprehensive account of the properties of microemulsions, including most recent developments and bringing them together from a united viewpoint, with an emphasis on how this affects the way of formulating microemulsions for a given application with desired properties.

Microwave-assisted Preparation of Cross-linked Gelatin-Paracetamol Matrices: Optimization Using the D-optimal Design

Objectives

This study was conducted to assess the effect of microwave heating on the preparation of paracetamol cross-linked gelatin matrices by using the design of experiment (DoE) approach and explore the influence of the duration of microwave irradiation, the concentrations of crosslinker, and the amount of sodium bicarbonate (salt) on paracetamol release. These parameters were also compared with those of the matrices prepared via conventional heating.

Materials and Methods

Twenty gel matrices were prepared with different durations of microwave irradiation, amounts of maize, and concentrations of sodium bicarbonate as suggested by Design Expert (DX®). The percentage drug release, the coefficient of variance (CV) in release, and the mean dissolution time (MDT) were the properties explored in the designed experimentation.

Results

Target responses were dependent on microwave irradiation time, cross-linker amount, and salt concentration. Classical and microwave heating did not demonstrate statistically significant difference in modifying the percentage of drug released from the matrices. However, the CVs of microwave-assisted formulations were lower than those of the gel matrices prepared via classical heating. Thus, microwave heating produced lesser variations in drug release. The optimized gel matrices demonstrated that the observed percentage of drug release, CV, and MDT were within the prediction interval generated by DX®. The release mechanism of the matrix formulations followed the Peppas-Korsmeyer anomalous transport model.

Conclusion

The DoE-supported microwave-assisted approach could be applied to optimize the critical factors of drug release with less variation.

InVitro, Ex Vivo, and In Vivo Evaluation of a Dual pH/Redox Responsive Nanoliposomal Sludge for Transdermal Drug Delivery

A dual pH/redox responsive copper-glyglycine-prednisolone succinate-loaded nanoliposomal (NL) sludge was successfully synthesized and optimized using a Box-Behnken design of experiments. Preformulation design variables indicated that relative ratios of phospholipids, considerably influences NL size, thus altering the degree of drug loading in the formulation. In vitro evaluation further confirmed optimum release kinetics of the NL sludge, corresponding closely to ex vivo permeation studies, demonstrating effective transdermal delivery of prednisone succinate (PS) through a pig skin model, which closely resembles human skin anatomy. The pH/redox stimuli responsiveness of the NL sludge further demonstrated superior properties in vivo using a Sprague-Dawley rat model. The NL sludge displayed the greatest release of PS within 24 h of evaluation, falling within the acceptable therapeutic range of PS dose efficiency. In vivo results further displayed the greatest absorption of PS under inflammatory induced conditions, thus confirming the unique pH/redox responsive properties of the NL sludge. It was thus confirmed that the copper-glyglycine-prednisolone succinate-loaded NL sludge has significant potential for application in chronic inflammatory conditions such as tumor necrosis factor receptor-associated periodic syndrome (TRAPS), designed to release an effective dose of corticosteroid, as a transdermal drug delivery formulation, for effective therapeutic efficacy.

Salicylate Poisoning Potential of Topical Pain Relief Agents: From Age Old Remedies to Engineered Smart Patches

The pain relief capabilities of methyl salicylate are well established and a multitude of over-the-counter products populate pharmacy shelves. Over-application of the topical preparation containing the drug, or its accidental ingestion, invariably result in salicylate poisoning and in severe cases can be fatal. The drug has been a regular feature of the US National Poison Database Survey over the past decade and continues to pose a risk to children and adults alike. The aim of the review has been to cast a spotlight on the drug and assess why its use remains problematic, how technology could offer more efficacious delivery regimes, and minimise the possibility of accidental or intentional misuse.

Advances in edible oleogel technologies - A decade in review

Trans and saturated fat replacers/substitutes have been a tremendously active area of research for the food industry. Unlike polymers used for hydrogels, oleogels utilize small, amphiphilic molecules that self-assemble via highly specific, non-covalent interactions entrapping liquid oil via capillary forces. Edible applications of oleogels have replaced the need for trans unsaturated and saturated fatty acids to structure processed foods. These innovations mitigate the use of hardstock fats that are associated with deleterious health risks and negative consumer perception. Over the past decade, oleogels have made significant strides towards emulating desired sensory traits while maintaining healthy nutritional profile of the oil. Due to the rapid advancements in the past decade, the most promising technologies will be reviewed.

Acyclovir-loaded sorbitan esters-based organogel: development and rheological characterization

Herein, a nanoemulsion-based organogel (NEOG) system loaded with acyclovir has been developed for the effective treatment of herpes simplex virus infection via topical delivery. Pseudo-ternary phase diagram exhibited increase in non-birefrigent, optically isotropic region of organogel with Smix (K_w) ratio. The NEOG C showed good storage (G') and loss moduli (G″), and more compact network structures. Gel-sol transition temperature (Tg) and fractal dimension (D_f) of NEOG system revealed increased density of the tubular network with K_w. Hence, high gelling ability of the developed NEOG system may attribute to the combination of sustained and site-specific delivery of drugs.

Controlled Aloin Release from Crosslinked Polyacrylamide Hydrogels: Effects of Mesh Size, Electric Field Strength and a Conductive Polymer

The aim of this paper is to investigate the effects of hydrogel mesh size, a conductive polymer, and electric field strength on controlled drug delivery phenomena using drug-loaded polyacrylamide hydrogels prepared at various crosslinking ratios both with and without a conductive polymer system. Poly(p-phenylene vinylene), PPV, as the model conductive polymer, was used to study its ability to control aloin released from aloin-doped poly(p-phenylene vinylene)/polyacrylamide hydrogel (aloin-doped PPV/PAAM). In the passive release, the diffusion of aloin from five aloin-doped PPV/PAAM hydrogel systems each was delayed ranging from during the first three hours to during the first 14 h due to the ionic interaction between the anionic drug and PPV. After the delayed periods, aloin could diffuse continuously into the buffer solution through the PAAM matrix. The amount of aloin released from the aloin-doped PPV/PAAM rose with increasing electric field strength as a result of the three mechanisms: the expansion of PPV chains inside the hydrogel, iontophoresis, and the electroporation of the matrix pore size, combined. Furthermore, the conductive polymer and the electric field could be used in combination to regulate the amount of release drug to a desired level, to control the release rate, and to switch the drug delivery on/off.

Recent advances in gel technologies for topical and transdermal drug delivery

Transdermal drug delivery systems are a constant source of interest because of the benefits that they afford in overcoming many drawbacks associated with other modes of drug delivery (i.e. oral, intravenous). Because of the impermeable nature of the skin, designing a suitable drug delivery vehicle that penetrates the skin barrier is challenging. Gels are semisolid formulations, which have an external solvent phase, may be hydrophobic or hydrophilic in nature, and are immobilized within the spaces of a three-dimensional network structure. Gels have a broad range of applications in food, cosmetics, biotechnology, pharmatechnology, etc. Typically, gels can be distinguished according to the nature of the liquid phase, for example, organogels (oleogels) contain an organic solvent, and hydrogels contain water. Recent studies have reported other types of gels for dermal drug application, such as proniosomal gels, emulgels, bigels and aerogels. This review aims to introduce the latest trends in transdermal drug delivery via traditional hydrogels and organogels and to provide insight into the latest gel types (proniosomal gels, emulgels, bigels and aerogels) as well as recent technologies for topical and transdermal drug delivery.

Electric field-controlled benzoic acid and sulphanilamide delivery from poly(vinyl alcohol) hydrogel

The controlled release of benzoic acid (3.31 Å) and sulphanilamide (3.47 Å) from poly(vinyl alcohol), PVA, hydrogels fabricated by solution casting at various cross-linking ratios, were investigated. The PVA hydrogels were characterized in terms of the degree of swelling, the molecular weight between cross-links, and the mesh size. The drug release experiment was carried out using a modified Franz diffusion cell, at a pH value of 5.5 and at temperature of 37°C. The amount of drug release and the diffusion coefficients of the drugs from the PVA hydrogels increased with decreasing cross-linking ratio, as a larger mesh size was obtained with lower cross-linking ratios. With the application of an electric field, the amount of drug release and the diffusion coefficient increased monotonically with increasing electric field strength, since the resultant electrostatic force drove the ionic drugs from the PVA matrix. The drug size, matrix pore size, electrode polarity, and applied electric field were shown to be influential controlling factors for the drug release rate.

Development of span 80-tween 80 based fluid-filled organogels as a matrix for drug delivery

Background:

Organogels are defined as 3-dimensional networked structures which immobilize apolar solvents within them. These gelled formulations are gaining importance because of their ease of preparation and inherent stability with improved shelf life as compared to the ointments.

Aim:

Development of span 80–tween 80 mixture based organogels for the first time by fluid-filled fiber mechanism.

Materials and Methods:

Span 80 and tween 80 were used as surfactant and co-surfactant, respectively. The surfactant mixtures were dissolved in oil followed by the addition of water which led to the formation of organogels at specific compositions. The formulations were analyzed by microscopy, X-ray diffraction (XRD), time-dependent stability test and accelerated thermal stability test by thermocycling method. Ciprofloxacin, a fourth-generation fluoroquinolone, was incorporated within the organogels. The antimicrobial activity of the drug loaded organogels and in vitro drug release from the gels was also determined.

Results and Conclusions:

Microscopic results indicated that the gels contained clusters of water-filled spherical structures. XRD study indicated the amorphous nature of the organogels. The release of the drug was found to be diffusion controlled and showed marked antimicrobial property. In short, the prepared organogels were found to be stable enough to be used as pharmaceutical formulation.

Effects of crosslinking ratio, model drugs, and electric field strength on electrically controlled release for alginate-based hydrogel

The drug release characteristics of calcium alginate hydrogels, (Ca-Alg), under an electric field assisted transdermal drug delivery system were systematically investigated. The Ca-Alg hydrogels were prepared by the solution-casting using CaCl(2) as a crosslinking agent. The diffusion coefficients and the release mechanism of the anionic model drugs, benzoic acid and tannic acid, and a cationic model drug, folic acid on the Ca-Alg hydrogels were determined and investigated using a modified Franz-Diffusion cell in an MES buffer solution of pH 5.5, at a temperature of 37°C, for 48 h. The influences of the crosslinking ratio, -the mole of the crosslinking agent to the mole of the alginate monomer-mesh size, model drug size, drug charge, electric field strength, and electrode polarity were systematically studied. The drug diffusion coefficient decreased with an increasing crosslinking ratio and drug size for all of the model drugs. The drug diffusion coefficient is precisely controlled by an applied electric field and the electrode polarity depending on the drug charge, suitable for a tailor-made transdermal drug delivery system.

Lecithin-linker microemulsion gelatin gels for extended drug delivery

This article introduces the formulation of alcohol-free, lecithin microemulsion-based gels (MBGs) prepared with gelatin as gelling agent. The influence of oil, water, lecithin and hydrophilic and lipophilic additives (linkers) on the rheological properties and appearance of these gels was systematically explored using ternary phase diagrams. Clear MBGs were obtained in regions of single phase microemulsions (μEs) at room temperature. Increasing the water content in the formulation increased the elastic modulus of the gels, while increasing the oil content had the opposite effect. The hydrophilic additive (PEG-6-caprylic/capric glycerides) was shown to reduce the elastic modulus of gelatin gels, particularly at high temperatures. In contrast to anionic (AOT) μEs, the results suggest that in lecithin (nonionic) μEs, the introduction of gelatin “dehydrates” the μE. Finally, when the transdermal transport of lidocaine formulated in the parent μE and the resulting MBG were compared, only a minor retardation in the loading and release of lidocaine was observed.

Preparation and evaluation of microemulsion systems containing salicylic acid

Microemulsions (MEs) are clear, thermodynamically stable systems. They were used to solubilize drugs and to improve topical drug availability. Salicylic acid (SA) is a keratolytic agent used in topical products with antimicrobial actions. The objective of this work was to prepare and evaluate SA ME systems. Different concentrations of SA were incorporated in an ME base composed of isopropyl myristate, water, and Tween 80: propylene glycol in the ratio of 15:1. Three ME systems were prepared: S2%, S5%, and S10% which contain 2%, 5%, and 10% of SA, respectively. Evaluation by examination under cross-polarizing microscope, measuring of percent transmittance, pH measurement, determination of the specific gravity, assessment of rheological properties, and accelerated stability study were carried out. The data showed that the addition of SA markedly affected the physical properties of the base. All systems were not affected by accelerated stability tests. Stability study for 6 months under ambient conditions was carried out for S10%. No remarkable changes were recorded except a decrease in the viscosity value after 1 month. The results suggested that ME could be a suitable vehicle for topical application of different concentrations of SA.