Microemulsions for topical delivery of estradiol

Microemulsion-Based Polymer Gels with Ketoprofen and Menthol: Physicochemical Properties and Drug Release Studies

Ketoprofen is a non-steroidal, anti-inflammatory drug frequently incorporated in topical dosage forms which are an interesting alternatives for oral formulations. However, due to the physiological barrier function of skin, topical formulations may require some approaches to improve drug permeation across the skin. In this study, ketoprofen-loaded microemulsion-based gels with the addition of menthol, commonly known for absorption-enhancing activity in dermal products, were investigated. The main objective of this study was to analyze the physicochemical properties of the obtained gels in terms of topical application and to investigate the correlation between the gel composition and its mechanical properties and the drug release process. Microemulsion composition was selected with the use of a pseudoternary plot and the selected systems were tested for electrical conductivity, viscosity, pH, and particle diameter. The polymer gels obtained with Carbopol® EZ-3 were subjected to rheological and textural studies, as well as the drug release experiment. The obtained results indicate that the presence of ketoprofen slightly decreased yield stress values. A stronger effect was exerted by menthol presence, even though it was independent of menthol concentration. A similar tendency was seen for hardness and adhesiveness, as tested in texture profile analysis. Sample cohesiveness and the drug release rate were independent of the gel composition.

Non-Invasive Delivery of Insulin for Breaching Hindrances against Diabetes

Insulin is recognized as a crucial weapon in managing diabetes. Subcutaneous (s.c.) injections are the traditional approach for insulin administration, which usually have many limitations. Numerous alternative (non-invasive) slants through different routes have been explored by the researchers for making needle-free delivery of insulin for attaining its augmented absorption as well as bioavailability. The current review delineating numerous pros and cons of several novel approaches of non-invasive insulin delivery by overcoming many of their hurdles. Primary information on the topic was gathered by searching scholarly articles from PubMed added with extraction of data from auxiliary manuscripts. Many approaches (discussed in the article) are meant for the delivery of a safe, effective, stable, and patient friendly administration of insulin via buccal, oral, inhalational, transdermal, intranasal, ocular, vaginal and rectal routes. Few of them have proven their clinical efficacy for maintaining the glycemic levels, whereas others are under the investigational pipe line. The developed products are comprising of many advanced micro/nano composite technologies and few of them might be entering into the market in near future, thereby garnishing the hopes of millions of diabetics who are under the network of s.c. insulin injections.

A Study of Microemulsion Systems for Transdermal Delivery of Risperidone Using Penetration Enhancers

The aim of this study was to develop and characterize microemulsion formulations using penetration enhancers as potential transdermal delivery systems for risperidone. Initially, a simple formulation of risperidone in Propylene Glycol (PG) was prepared as a control formulation, together with formulations incorporating various penetration enhancers, alone and/or in combination, and also microemulsion formulations with various chemical penetration enhancers, were prepared and all were evaluated for risperidone transdermal delivery. An ex-vivo permeation study was carried out using human cadaver skin and vertical glass Franz diffusion cells to compare all the microemulsion formulations. The microemulsion prepared from oleic acid as the oil (15%), Tween 80 (15%) as the surfactant and isopropyl alcohol (20%) as the co-surfactant, and water (50%) showed higher permeation with a flux value of 32.50±3.60 ug/hr/sq.cm, a globule size of 2.96±0.01 nm, a polydispersity index of 0.33±0.02 and pH of 4.95. This novel in vitro research disclosed that an optimized microemulsion formulated using penetration enhancers was able to increase permeation of risperidone by 14-fold compared to the control formulation. The data suggested that microemulsions may be useful in the delivery of risperidone via the transdermal route.

Crisaborole loaded nanoemulgel for the mitigation of atopic dermatitis in mice model

OBJECTIVE

The present work aims to formulate nanoemulgel of crisaborole (CB) and evaluate its effectiveness against 2,4-Di-nitrochlorobenzene induced (DNCB) atopic dermatitis (AD) in mice.

SIGNIFICANCE

AD is a chronic inflammation of the skin affecting the quality of life. CB is a topical PDE4 inhibitor marketed as a 2% ointment. It, however, possesses poor aqueous solubility. An o/w nanoemulsion shall exhibit an enhanced therapeutic effect owing to the increased solubility of CB and an augmented skin penetration. The addition of a gelling agent to form a nanoemulgel further provides ease of application to the patients.

METHODS

Nanoemulsion was prepared by aqueous titration method using caproyl PGMC, cremophore EL and propylene glycol as the oil, surfactant, and cosurfactant respectively. The formulations were characterized by their size, zeta potential and polydispersity index (PDI). 1% Carbopol 934 was used as the gelling agent to formulate nanoemulgel comprising of optimized nanoemulsion (NE 9). Ex vivo skin permeation of the CB nanoemulgel was compared with the CB ointment. Its therapeutic effect was evaluated in Balb/c mice.

RESULTS

NE 9 comprised of 7.49% oil, 37.45% Smix (1:3) and water 55.06%. Its particle size, PDI and zeta potential were 15.45 ± 5.265 nm, 0.098 and -17.9 ± 8.00 mV respectively. The nanoemulgel exhibited a 3-fold higher permeation flux as compared to the ointment. In vivo studies demonstrated that the nanoemulgel provided better therapeutic effect than the ointment.

CONCLUSION

We can thereby conclude that nanoemulgel formulation can be a successful drug delivery strategy for enhancing the therapeutic effect of CB.

Facile preparation of a novel nanoemulsion based hyaluronic acid hydrogel loading with Poria cocos triterpenoids extract for wound dressing

Diabetic wounds have been a serious concern for human health owing to their long chronic inflammation and reduced vascularization. Herein, we report novel oil-in-water (o/w) nanoemulsions (NEs) containing Poria cocos triterpenes extract (PTE) to fabricate hyaluronic acid hydrogels (PTE-NEs) for the treatment of diabetic wounds. The size and morphology of NEs are analyzed by transmission electron microscope (TEM) and Zeta potential, respectively. Furthermore, the rheological behavior and morphology of synthesized hydrogels are also determined. It is found that PTE-NEs gel has a homogeneous and porous structure with good elastic properties. In addition, in vitro experiments show that the cell viability of PTE-NEs gel is >85 % without cytotoxicity. In vivo experiments of diabetic rats demonstrate that the PTE-NEs gel can not only significantly accelerate diabetic wound healing, collagen deposition, M2 macrophage polarization, and angiogenesis, but also inhibit inflammation. In conclusion, PTE plays a significant role in wound healing and exhibits anti-inflammatory effects, demonstrating its great potential in treating diabetic wounds.

Monolaurin-Loaded Gel-Like Microemulsion for Oropharyngeal Candidiasis Treatment: Structural Characterisation and In Vitro Antifungal Property

Recently, monolaurin (ML) has received great interest due to its possible use as an alternative antifungal. However, the limited water solubility of ML is still a major obstacle to its formulation and application. Gel-like microemulsions are one of the promising carriers for low-water-solubility substances due to both the advantages of gels and microemulsions and may be applied for ML. In this study, ML was incorporated into gel-like microemulsions and evaluated for its physicochemical and antifungal properties. The results indicated that the properties of gel-like microemulsion changed after the incorporation of ML, suggesting that ML can induce the transition of internal structure. When simulating the oral cavity environment, changes in the microstructure were observed and depended on the times of dilution. The lamellar structure was formed at 1.5-2 times dilution. However, this structure was disrupted after dilution five times or more. The structural change following dilution was associated with the release profiles. After contacting the formulations with the medium, ML was promptly released, with the majority of ML being released within 2 h. Regarding the antifungal assay, the ML-loaded gel-like microemulsions decreased the survival of Candida albicans within 3 h, although ML was immediately released, suggesting that the ML-loaded in oil droplets required time to permeate through the fungal cell wall. Additionally, the gel-like microemulsions possessed acceptable stability after the temperature cycling test. Therefore, gel-like microemulsions can be a possible carrier for ML loading, and ML-loaded gel-like microemulsions may be applied as an alternative antifungal preparation in the future. Graphical abstract.

Continuous production of nanoemulsion for skincare product using a 3D-printed rotor-stator hydrodynamic cavitation reactor

In this study, nanoemulsions for skincare products were continuously produced using a hydrodynamic cavitation reactor (HCR) designed with a rotor and stator. The key component of this research is the utilization of a 3D-printed rotor in a HCR for the production of an oil-in-water nanoemulsion. Response surface methodology was used to determine the process conditions, such as speed of the rotor, flow rate, as well as, Span60, Tween60, and mineral oil concentrations, for generating the optimal droplet size in the nanoemulsion. The results showed that a droplet size of 366.4 nm was achieved under the recommended conditions of rotor speed of 3500 rpm, flow rate of 3.3 L/h, Span60 concentration of 2.36 wt%, Tween60 concentration of 3.00 wt%, and mineral oil concentration of 1.76 wt%. Moreover, the important characteristics for consideration in skincare products, such as polydispersity index, pH, zeta potential, viscosity, stability, and niacin released from formulations, were also assessed. For the niacin release profile of emulsion and nanoemulsion formulations, different methods, such as magnetic stirring, ultrasound, and hydrodynamic cavitation, were compared. The nanoemulsion formulations provided a greater cumulative release from the formulation than the emulsion. Particularly, the nanoemulsion generated using the HCR provided the largest cumulative release from the formulation after 12 h. Therefore, the present study suggests that nanoemulsions can be created by means of hydrodynamic cavitation, which reduces the droplet size, as compared to that generated using other techniques. The satisfactory results of this study indicate that the rotor-stator-type HCR is a potentially cost-effective technology for nanoemulsion production.

Azelaic acid and Melaleuca alternifolia essential oil co-loaded vesicular carrier for combinational therapy of acne

Aim: Azelaic acid (AzA), a comedolytic, antibacterial, anti-inflammatory anti-melanogenic agent, prescribed against acne vulgaris is safe on skin. Its combination with another widely used anti-acne agent, tea tree oil (EO) whose delivery is limited by volatility, instability and lipophilicity constraints was attempted. Method: Solvent injection was used to prepare AzA-EO integrated ethosomes. Result: Ethosomes were transformed into carbopol hydrogel, which exhibited pseudo-plastic properties with appreciable firmness, work of shear, stickiness and work of adhesion. The hydrogel showed better permeation and retention characteristics vis-a-vis commercial formulation (AzidermTM), when evaluated in Wistar rat skin. Further, ethosome hydrogel composite was better tolerated with no side effects. Conclusion: The findings suggests that the aforementioned strategy could be a potential treatment used for acne management.

Preparation and Characterization of Curcumin Nanoemulgel Utilizing Ultrasonication Technique for Wound Healing: In Vitro, Ex Vivo, and In Vivo Evaluation

Hydrogels being a drug delivery system has great significance particularly for topical application in cutaneous open wound. Its specific physicochemical properties such as non-adhesiveness, moisture retention, exudate absorption, and gas permeability make them ideal as a drug delivery vehicle for wound healing application. Further, curcumin (a natural bioactive) was selected as a therapeutic agent to incorporate into the hydrogel system to design and develop nanogel pharmaceutical products for wound healing. Although, curcumin possesses remarkable anti-inflammatory, antioxidant, and anti-infective activity along with hastening the healing process by acting over the different stages of the wound healing process, but its poor biopharmaceutical (low aqueous solubility and skin penetrability) attributes hamper their therapeutic efficacy for skin applications. The current investigation aimed to develop the curcumin-loaded nanogel system and evaluated to check the improvement in the therapeutic efficacy of curcumin through a nanomedicine-based approach for wound healing activity in Wistar rats. The curcumin was enclosed inside the nanoemulsion system prepared through a high-energy ultrasonic emulsification technique at a minimum concentration of surfactant required to nanoemulsify the curcumin-loaded oil system (Labrafac PG) having droplet size 56.25 ± 0.69 nm with polydispersity index 0.05 ± 0.01 and negatively surface charge with zeta potential −20.26 ± 0.65 mV. It was observed that the impact of Smix (surfactant/co-surfactant mixture) ratio on droplet size of generated nanoemulsion is more pronounced at lower Smix concentration (25%) compared to the higher Smix concentration (30%). The optimized curcumin-loaded nanoemulsion was incorporated into a 0.5% Carbopol^® 940 hydrogel system for topical application. The developed curcumin nanoemulgel exhibited thixotropic rheological behavior and a significant (p < 0.05) increase in skin penetrability characteristics compared to curcumin dispersed in conventional hydrogel system. The in vivo wound healing efficacy study and histological examination of healed tissue specimen further signify the role of the nanomedicine-based approach to improve the biopharmaceutical attributes of curcumin.

Microemulsions: Unique Properties, Pharmacological Applications, and Targeted Drug Delivery

Microemulsions, comprising oil, water and a surfactant, in association with some co-surfactant, are thermodynamically stable systems. They have found applications in a large number of chemical and pharmacological processes due to their unique properties such as large interfacial area, low interfacial tension, and most importantly, the ability to solubilize and deliver hydrophobic drugs. In addition to the oral and intravenous route, they are suitable for drug delivery through the ophthalmic, vaginal, pulmonary, dental, and topical routes. This review highlights the properties and several recent developments in the use of microemulsions for medical treatment purposes including targeted drug delivery.

Advances and challenges in nintedanib drug delivery

INTRODUCTION

Nintedanib (N.T.B) is an orally administered tyrosine kinase inhibitor that has been approved recently by U.S.F.D.A for idiopathic pulmonary fibrosis (I.P.F) and systemic sclerosis-associated interstitial lung disease (S.Sc-I.L.D). N.T.B is also prescribed in COVID-19 patients associated with I.P.F. However, it has an extremely low bioavailability of around 4.7%, and hence, researchers are attempting to address this drawback by different approaches.

AREAS COVERED

This review article focuses on enlisting all the formulation attempts explored by researchers to increase the bioavailability of N.T.B while also providing meaningful insight into the unexplored areas in formulation development, such as targeting of the lymphatic system and transdermal delivery. All the patents on the formulation development of N.T.B have also been summarized.

EXPERT OPINION

N.T.B has the potential to act on multiple diseases that are still being discovered, but its extremely low bioavailability is a challenge that is to be dealt with for obtaining the full benefit. Few studies have been performed aiming at improving the bioavailability, but there are unexplored areas that can be used, a few of which are explained in this article. However, the ability to reproduce laboratory results when scaling up to the industry level is the only factor to be taken into consideration.

Permeation, stability and acute dermal irritation of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica crude extract loaded transdermal gels

In this study, permeation behaviors and chemical stability of miroestrol and deoxymiroestrol from Pueraria candollei var. mirifica (PM), Thai traditional medicine, crude extract containing transdermal gels were firstly evaluated. Three different PM extract containing gels were formulated, including hydroalcoholic and microemulsion gels using carbomer, and silicone gel using silicone elastomer. In vitro permeation through porcine ear skin demonstrated that the flux and 24 h cumulative permeation of miroestrol and deoxymiroestrol were in the order of hydroalcoholic > silicone > microemulsion gels. Hydroalcoholic gel provided the highest partition coefficient from gel onto skin, and thus the skin permeability coefficient. After 24 h permeation, no miroestrol and deoxymiroestrol remained deposited in the skin. Accelerated study using heating-cooling revealed insignificant difference between the remaining percentages of miroestrol and deoxymiroestrol in aqueous and non-aqueous based gels. Long-term stability study showed that miroestrol contents remained constant for 90 d and 30 d under 5 ± 3 °C and 30 ± 2 °C, 75 ± 5%RH, respectively; whereas the percentage of deoxymiroestrol decreased significantly after 30 d storage, irrespective of storage conditions. Acute dermal irritation test on New Zealand White rabbits showed that PM hydroalcoholic gels were non-irritant, with no signs of erythema or oedema.[Figure: see text].

Potential of nanoparticulate based delivery systems for effective management of alopecia

In recent times, more than 50 % of the global population is facing hair-related issues (alopecia) which is seen mostly amongst the people in the age group of 30-40 years. The conventional topical dosage forms available in the market falls short in effectively managing alopecia. Despite various advancements in topical dosage forms, it is still disposed to limited clinical application and provides poor penetration of drug molecules into the skin. The exact etiology of alopecia is still unknown and various researchers link lifestyle, hereditary, and auto immune-based events with its existence. Nanoparticulate-based delivery are hence brought in use to enhance the permeability properties of the drug. In comparison to conventional methods nanotechnology-based drug delivery system tames drug molecules to a specific site with much better efficacy. This review is engrossed in the journey and role of nano technological-based drug delivery in the management of alopecia and its clinical application.

Delivery of Insulin via Skin Route for the Management of Diabetes Mellitus: Approaches for Breaching the Obstacles

Insulin is used for the treatment of diabetes mellitus, which is characterized by hyperglycemia. Subcutaneous injections are the standard mode of delivery for insulin therapy; however, this procedure is very often invasive, which hinders patient compliance, particularly for individuals requiring insulin doses four times a day. Furthermore, cases have been reported of sudden hypoglycemia occurrences following multidose insulin injections. Such an invasive and intensive approach motivates the quest for alternative, more user-friendly insulin administration approaches. For example, transdermal delivery has numerous advantages, such as prolonged drug release, low variability in the drug plasma level, and improved patient compliance. In this paper, the authors summarize different approaches used in transdermal insulin delivery, including microneedles, chemical permeation enhancers, sonophoresis, patches, electroporation, iontophoresis, vesicular formulations, microemulsions, nanoparticles, and microdermabrasion. Transdermal systems for insulin delivery are still being widely researched. The conclusions presented in this paper are extracted from the literature, notably, that the transdermal route could effectively and reliably deliver insulin into the circulatory system. Consistent progress in this area will ensure that some of the aforementioned transdermal insulin delivery systems will be introduced in clinical practice and commercially available in the near future.

Nanostructured Lipid Carrier-Mediated Transdermal Delivery of Aceclofenac Hydrogel Present an Effective Therapeutic Approach for Inflammatory Diseases

Aceclofenac (ACE), a cyclooxygenase-2 inhibitor, is the derivative of the diclofenac group that has been in use for the symptomatic treatment of systemic inflammatory autoimmune disease, rheumatoid arthritis (RA). Partial solubility, high lipophilic nature, and stability challenge its use in developing topical formulations. Hence, we developed and characterized nanostructured lipid carrier (NLC)-based ACE (ACE-NLC) hydrogel for an efficient transdermal delivery. NLC microemulsion was prepared using different lipids by various methods and was characterized with respect to particle size, zeta potential, surface morphology, and drug encapsulation efficiency. The optimized NLC formulation was incorporated into Carbopol^® 940 gel, and this arrangement was characterized and compared with the existing marketed gel (Mkt-gel) formulation to assess in vitro drug release, rheology, texture profile, in vivo skin retention and permeation, and stability. Furthermore, prepared and characterized ACE-loaded NLC formulation was evaluated for skin integrity and fitted in a dermatokinetic model. The results of this study confirmed the spherical shape; smooth morphology and nanometric size attested by Zetasizer and scanning and transmission electron microcopy; and stability of the ACE-NLC formulation. The ACE-NLC-gel formulation showed good rheological and texture characteristics, and better skin distribution in the epidermis and dermis. Moreover, ACE-NLC permeated deeper in the skin layers and kept the skin integrity intact. Overall, NLC-based gel formulation of ACE might be a promising nanoscale lipid carrier for topical application when compared with the conventional Mkt-gel formulation.

A Novel Nanoemulsion Intermediate Gel as a Promising Approach for Delivery of Itraconazole: Design, In Vitro and Ex Vivo Appraisal

The aim the study was to design, formulate, and evaluate self-nanoemulsifying drug delivery systems (SNEDDS) of itraconazole for improving the topical antifungal properties of the drug by adopting the nanoemulsion intermediate gel of the optimized system. Solubility study was conducted to select the most appropriate oils and surfactants for formulation. Different possible systems were created. Ternary phase diagrams were constructed to select the most promising system for further study. The nanoemulsion intermediate gel of the selected system was evaluated for stability, dilution effect, viscosity, pH, antifungal activity, droplet size, PDI, and zeta potential. In vitro release of the drug from the selected intermediate gel was investigated, and the kinetic model of drug release was determined. Ex vivo permeation of itraconazole was studied, and the amount of drug accumulated in the skin was calculated. Solubility and phase diagrams revealed that the system consisting of 60% cotton seed oil and 40% span 80 provided the nanoemulsion intermediate gel with the highest drug concentration. The selected system had a droplet size of about 236 nm and zeta potential of - 59.8. The viscosity of the corresponding intermediate gel was 1583.47 cp. The system exhibited high stability at 4°C and 25°C for 12 months and improved antifungal activity. In vitro release study showed complete release of itraconazole within 4 h, while the ex vivo permeation study revealed accumulation of the majority of the drug within the skin layers (72.5%).

Transdermal co-delivery of glucosamine sulfate and diacerein for the induction of chondroprotection in experimental osteoarthritis

The aim of this work was to develop a transdermal delivery system consisting of a glucosamine sulfate-laden xanthan hydrogel containing a nanoemulsion-loaded diacerein. The system was intended to prevent cartilage degradation typical of osteoarthritis. The nanoemulsion, made of soybean oil as the oil phase; soybean lecithin, Tween 80, and poloxamer 407 as surfactants; and propylene glycol as cosurfactant, was formed within the hydrogel. The hydrodynamic diameter of the nanoemulsion globules was 81.95 ± 0.256 nm with 0.285 ± 0.036 of PDI value and the zeta potential value of the formulation was 39.33 ± 0.812 mV. CryoSEM and TEM studies revealed the uniform morphology of the vehicle. A rheological study exposed the nanoemulsion-loaded hydrogel as a thixotropic system. Satisfactory storage stability under ICH conditions was established by the zeta potential and rheological studies. Furthermore, skin biocompatibility of the hydrogel was ascertained on the basis of skin irritation study. Additionally, the diffusion of the drugs across rat skin followed a controlled non-Fickian anomalous steady mechanism. Following in vivo administration in experimental osteoarthritis, the transdermal hydrogel showed a reduction in tumor necrosis factor-alpha, C-reactive protein, high mobility group box protein, and monocyte chemoattractant protein-1. Finally, histopathological analysis of the animals showed satisfactory chondroprotection in the in vivo study. In conclusion, the developed transdermal systems showed a potential against the progression of experimental osteoarthritis.

Using Microemulsion as Carrier for Drug Transdermal Delivery: The Effect of Surfactants and Cosurfactants

BACKGROUND

The purpose of this study was to evaluate the effect of types of surfactants and cosurfactants on physicochemical properties and permeability of sumatriptan-loaded microemulsions through rat skin.

METHODS

Different types of surfactants and cosurfactants were used to prepare drug-loaded microemulsions. The physicochemical characters and permeability parameters of these formulations were measured.

RESULTS

The experimental microemulsions with varying components had small droplet size ranging from 24.6 nm to 2568.8 nm, low viscosity ranging from 7.49 to 43.34 cps and significant permeation enhancement ratio ranging from 23.0 to 98.6 when compared to the control group.

CONCLUSION

The composition and proportion of surfactants and cosurfactants were key factors for the physiochemical properties of drug-loaded microemulsions. The cumulative transdermal amount of the microemulsion containing mixture surfactant of Laureth-3/Laureth-23 was higher than that of the microemulsion with a mixture of Tween 80/Span 20. In the selected cosurfactant, diethylene glycol monoethyl ether (DEGMEE) showed highest permeation enhancement. Thermodynamic stability tests revealed that the experimental microemulsion was a stable enough formulation to be considered as a suitable carrier for sumatriptan.

Improvements in chemical carriers of proteins and peptides

The successful intracellular delivery of biologically active proteins and peptides plays an important role for therapeutic applications. Indeed, protein/peptide delivery could overcome some problems of gene therapy, for example, controlling the expression levels and the integration of transgene into the host cell genome. Thus, protein/peptide drug delivery showed a promising and safe approach for treatment of cancer and infectious diseases. Due to the unique physical and chemical properties of proteins, their production (e.g., isolation, purification & formulation) and delivery represented significant challenges in pharmaceutical studies. Modification in the structural moieties of these protein/peptide drugs could improve their solubility, stability, crystallinity, lipophilicity, enzymatic susceptibility and targetability, and subsequently, therapies and cures against various diseases. Using the structural modification of protein/peptide, their delivery provided overall higher success rates including high specificity, high activity, bioreactivity and safety. Recently, biotechnological and pharmaceutical companies have tried to find novel techniques for the modifications and improve delivery systems/carriers. However, each carrier has its own benefits and drawbacks, and an appropriate carrier is often established by the physicochemical properties of protein or peptide, the ideal route of injection, and clinical characteristics of therapy. In this review, an attempt was made to give an overview on the chemical carriers for proteins and peptides as well as the recent advances in this field.

Biomedical applications of microemulsion through dermal and transdermal route

Microemulsions are thermodynamically stable, transparent, colloidal drug carrier system extensively used by the scientists for effective drug delivery across the skin. It is a spontaneous isotropic mixture of lipophilic and hydrophilic substances stabilized by suitable surfactant and co-surfactant. The easy fabrication, long-term stability, enhanced solubilization, biocompatibility, skin-friendly appearance and affinity for both the hydrophilic and lipophilic drug substances make it superior for skin drug delivery over the other carrier systems. The topical administration of most of the active compounds is impaired by limited skin permeability due to the presence of skin barriers. In this sequence, the microemulsion represents a cost-effective and convenient drug carrier system which successfully delivers the drug to and across the skin. In the present review work, we compiled various attempts made in last 20 years, utilizing the microemulsion for dermal and transdermal delivery of various drugs. The review emphasizes the potency of microemulsion for topical and transdermal drug delivery and its effect on drug permeability.

Getting the Jump on the Development of Bullfrog Oil Microemulsions: a Nanocarrier for Amphotericin B Intended for Antifungal Treatment

Amphotericin B (AmB), a potent antifungal drug, presents physicochemical characteristics that impair the development of suitable dosage forms. In order to overcome the AmB insolubility, several lipid carriers such as microemulsions have been developed. In this context, the bullfrog oil stands out as an eligible oily phase component, since its cholesterol composition may favor the AmB incorporation. Thus, the aim of this study was to develop a microemulsion based on bullfrog oil containing AmB. Moreover, its thermal stability, antifungal activity, and cytotoxicity in vitro were evaluated. The microemulsion formulation was produced using the pseudo-ternary phase diagram (PTPD) approach and the AmB was incorporated based on the pH variation technique. The antifungal activity was evaluated by determination of minimal inhibitory concentration (MIC) against different species of Candida spp. and Trichosporon asahii. The bullfrog oil microemulsion, stabilized with 16.8% of a surfactant blend, presented an average droplet size of 26.50 ± 0.14 nm and a polydispersity index of 0.167 ± 0.006. This system was able to entrap AmB up to 2 mg mL^-1. The use of bullfrog oil as oily phase allowed an improvement of the thermal stability of the system. The MIC assay results revealed a growth inhibition for different strains of Candida spp. and were able to enhance the activity of AmB against T. asahii. The microemulsion was also able to reduce the AmB toxicity. Finally, the developed microemulsion showed to be a suitable system to incorporate AmB, improving the system's thermal stability, increasing the antifungal activity, and reducing the toxicity of this drug.

Microemulsion Formulations for the Transdermal Delivery of Lapachol

This project was carried out to investigate the feasibility of using microemulsions for transdermal delivery of lapachol. From the screening of surfactants and oils, a range of microemulsions were developed using oleic acid, a mixture of Cremophor EL and Tween 20 and water. The solubility of lapachol was determined in these ingredients and in the formulated microemulsions. The microemulsions were characterised using cross-polarising light microscopy, their electrical conductivity, pH, zeta potential and rheology were analysed, and they were also investigated using small-angle X-ray scattering and differential scanning calorimetry. Ex vivo studies were performed using porcine ear skin and Franz diffusion cells to investigate the permeation and retention of lapachol. Systems containing different concentrations of Cremophor EL (8.4-41.6%), Tween 20 (5.4-41.6%) and oleic acid (12-31.9%) are able to form microemulsions. Lapachol was delivered more effectively through the skin from all of the microemulsions tested than by the control (oleic acid). These studies indicated that microemulsions incorporating lapachol were formed successfully and that these enhanced drug delivery and retention in the skin. Microemulsion systems may, therefore, provide promising vehicles for percutaneous delivery of lapachol.

Design and Development of Repaglinide Microemulsion Gel for Transdermal Delivery

Microemulsion formulation of repaglinide, a BCS class II hypoglycemic agent with limited oral bioavailability, was developed considering its solubility in various oils, surfactants, and cosurfactants. The pseudo-ternary phase diagrams for microemulsion regions were constructed by water titration method at K _m 1:1 and characterized for optical birefringence, percentage transmittance, pH, refractive index, globule size, zeta potential, viscosity, drug content, and thermodynamic stability. To enhance the drug permeation and residence time, the optimized microemulsions having mean globule size of 36.15 ± 9.89 nm was gelled with xanthan gum. The developed microemulsion-based gel was characterized for globule size, zeta potential, pH, and drug content. All evaluation parameters upon gelling were found to be satisfactory. Ex vivo permeability study across rat skin demonstrated higher steady-state flux (P < 0.05) for microemulsion of repaglinide in comparison to the repaglinide microemulsion gel. At the end of 24 h, the cumulative drug permeation from microemulsion and microemulsion gel was found to be 229.19 ± 24.34 and 180.84 ± 17.40 μg/cm², respectively. The microemulsion formulation showed 12.30-fold increase in flux as compared to drug suspension with highest enhancement ratio (E _r ) of 12.36. Whereas microemulsion gel exhibited 10.97-fold increase in flux (with highest E _r , 11.78) as compared to repaglinide (RPG) suspension. In vivo efficacy study was performed in normal Sprague-Dawley rats by using oral glucose tolerance test. Results of RPG transdermal microemulsion gel demonstrated remarkable advantage over orally administered RPG by reducing the glucose level in controlled manner. Hence, it could be a new, alternative dosage form for effective therapy of type 2 diabetes mellitus.

Prolonged skin retention of clobetasol propionate by bio-based microemulsions: a potential tool for scalp psoriasis treatment

Novel effective and cosmetically acceptable formulations are needed for the treatment of scalp psoriasis, due to the poor efficacy of the current products. The challenge in developing safe, efficient, and convenient delivery systems for this drug was addressed in the present work by formulating clobetasol propionate-loaded W/O microemulsions (MEs). Pseudo-ternary phase diagrams were constructed by using a combination of biocompatible and biodegradable excipients. Characterization studies demonstrated that selected MEs had suitable technological features such as being Newtonian fluids, possessing low viscosity, and high thermodynamic stability. Photomicrographs showed a significant alteration of the skin structure after treatment with MEs, and a preferential concentration of these in the stratum corneum and epidermis. These data, together with ex vivo permeation results, suggested an enhanced topical targeted effect due to an increased drug retention efficacy in the upper skin layers, as desired. Moreover, the bio-based excipients selected could contribute to the healing of the psoriatic scalp. In this way, the improvement of clobetasol efficacy is combined with the useful properties of the microemulsion components and with environmental safety.

Transdermal agomelatine microemulsion gel: pyramidal screening, statistical optimization and in vivo bioavailability

Agomelatine is a new antidepressant having very low oral drug bioavailability less than 5% due to being liable to extensive hepatic 1st pass effect. This study aimed to deliver agomelatine by transdermal route through formulation and optimization of microemulsion gel. Pyramidal screening was performed to select the most suitable ingredients combinations and then, the design expert software was utilized to optimize the microemulsion formulations. The independent variables of the employed mixture design were the percentages of capryol 90 as an oily phase (X1), Cremophor RH40 and Transcutol HP in a ratio of (1:2) as surfactant/cosurfactant mixture 'Smix' (X2) and water (X3). The dependent variables were globule size, optical clarity, cumulative amount permeated after 1 and 24 h, respectively (Q1 and Q24) and enhancement ratio (ER). The optimized formula was composed of 5% oil, 45% Smix and 50% water. The optimized microemulsion formula was converted into carbopol-based gel to improve its retention on the skin. It enhanced the drug permeation through rat skin with an enhancement ratio of 37.30 when compared to the drug hydrogel. The optimum ME gel formula was found to have significantly higher Cmax, AUC 0-24 h and AUC0-∞ than that of the reference agomelatine hydrogel and oral solution. This could reveal the prosperity of the optimized microemulsion gel formula to augment the transdermal bioavailability of agomelatine.

Design, Development, and Optimization of Dexibuprofen Microemulsion Based Transdermal Reservoir Patches for Controlled Drug Delivery

The aim of the study was to develop a reservoir-type transdermal patch for a controlled delivery of dexibuprofen and to evaluate its in vivo anti-inflammatory activity in Albino Wistar rats. In order to develop these patches, six formulations of dexibuprofen microemulsion comprising ethyl oleate, Tween 80: PG (2 : 1), and water were prepared by simplex lattice design and characterized. The reservoir compartment was filled with these microemulsions and in vitro release and skin permeation were assessed. The optimized patch was obtained on the basis of the responses: Q₂₄ and flux. The impact of drug loading, surface area, membrane thickness, adhesive, and agitation speed on drug release and permeation was also studied. The skin sensitivity reaction and in vivo anti-inflammatory activity of optimized patch were evaluated. Stability study at three different temperatures for three months was carried out. The result suggests that a membrane based patch with zero-order release rate, Q₂₄ of 79.13 ± 3.08%, and maximum flux of 331.17 µg/cm²h can be obtained exhibiting suitable anti-inflammatory activity with no visible skin sensitivity reaction. The outcomes of stability study recommend storage of patches at 4°C having shelf-life of 6.14 months. The study demonstrates that the reservoir-type transdermal patch of dexibuprofen microemulsion has a potential of delivering drug across skin in controlled manner with required anti-inflammatory activity.

Novel microemulsion-based gels for topical delivery of indomethacin: Formulation, physicochemical properties and in vitro drug release studies

HYPOTHESIS

Microemulsion-based semisolid systems may be considered as an interesting alternative to the traditional dosage forms applied in topical drug delivery. Mechanical properties of topical products are important both in terms of application and dosage form effectiveness. In this study we designed and evaluated novel microemulsion-based gels with indomethacin and analyzed the factors affecting their mechanical characteristics and drug release.

EXPERIMENTS

The impact of the microemulsion composition on the extent of isotropic region was investigated with the use of pseudoternary phase diagrams. Selected microemulsions were analyzed in terms of electrical conductivity and surface tension in order to determine the microemulsion type. Microemulsions were transformed into polymer-based gels and subjected to rheological and textural studies. Finally, the indomethacin release from the analyzed gels was studied and compared to commercially available product.

FINDINGS

The extent of isotropic domain in pseudoternary phase diagrams seems to be dependent on the polarity of the oil phase. The surface tension and conductivity monitored as a function of water content in microemulsion systems revealed possible structural transformations from w/o through bicontinuous systems into o/w. The mechanical properties of semisolid microemulsion-based systems depended on the composition of surface active agents and the drug presence. The drug release profiles observed in the case of the investigated gels differed from those recorded for the commercially available product which was most probably caused by the different structure of both systems.

Alkyl Protocatechuate-Loaded Nanostructured Lipid Systems as a Treatment Strategy for Paracoccidioides brasiliensis and Paracoccidioides lutzii In Vitro

Dodecyl protocatechuate (dodecyl) is a derivative of protocatechuic acid (3,4-dihydroxybenzoic acid) that possesses anti-oxidant and antifungal properties. Nanostructured lipid systems (NLS) can potentiate the action of many antifungal agents, reducing the required dose and side effects by improving their activity. This work aimed to evaluate dodecyl protocatechuate loaded into a NLS (NLS+dodecyl) as a strategy for the treatment of Paracoccidioides brasiliensis and P. lutzii in vitro. Antifungal activity against P. brasiliensis and P. lutzii was evaluated using the microdilution technique. NLS+dodecyl showed high antifungal activity with a minimum inhibitory concentration ranging from 0.06 to 0.03 μg/mL; 4- to 16-fold higher than that of free dodecyl. NLS+dodecyl was able to inhibit fungal adhesion of the extracellular artificial matrix proteins (laminin and fibronectin), resulting in 82.4 and 81% inhibition, respectively, an increase of 8–17% compared with free dodecyl. These findings corroborate previous results demonstrating 65 and 74% inhibition of fungal adhesion in pulmonary fibroblast cells by dodecyl and NLS+dodecyl, respectively, representing a 9% increase in inhibition for NLS+dodecyl. Subsequently, cytotoxicity was evaluated using the 0.4% sulforhodamine B assay. NLS+dodecyl did not exhibit cytotoxicity in MRC5 (human pneumocyte) and HepG2 (human hepatic carcinoma) cells, thus increasing the selectivity index for NLS+dodecyl. In addition, cytotoxicity was evaluated in vivo using the Caenorhabditis elegans model; neither dodecyl nor NLS+dodecyl exhibited any toxic effects. Taken together, these results suggest that NLS can be used as a strategy to improve the activity of dodecyl against P. brasiliensis and P. lutzii because it improves antifungal activity, increases the inhibition of fungal adhesion in lung cells and the extracellular matrix in vitro, and does not exhibit any toxicity both in vitro and in vivo.

Benzyl Benzoate-Loaded Microemulsion for Topical Applications: Enhanced Dermatokinetic Profile and Better Delivery Promises

Benzyl benzoate (BB) is one of the oldest drugs used for the treatment of scabies and is recommended as the "first-line intervention" for the cost-effective treatment of the disease. Though a promising candidate, its application is reported to be associated with irritation of the skin and eye, resulting in poor patient compliance. Hence, the present study aims to develop BB-loaded topical microemulsion for the safer and effective delivery of BB. Pseudo-ternary phase diagrams with BB as the oily phase itself, along with Tween 80 as surfactant, and mixture of phospholipid and ethanol as the co-surfactant along with aqueous solution as the external phase were constructed and various compositions were formulated. The optimized formulation was characterized for particle-size, zeta-potential, drug-content, globule-morphology pH, and refractive-index, whereas evaluated for skin permeation, retention, compliance, and dermatokinetics. The nanosized formulation offered threefold higher drug permeation vis-a-vis plain drug solution across LACA mice abdominal skin. The drug retention of the selected formulation was nearly twice of that from the marketed product, assuring depot formulation and sustained release. The skin histopathology revealed the non-irritant nature of the formulation, as no changes in the normal skin histology were observed. The dermatokinetic studies confirmed better permeation and enhanced skin bioavailability of BB to epidermis as well as dermis vis-à-vis the conventional product. The results indicate that the developed lipid-based microemulsion hydrogel can alleviate the concerns associated with BB and can provide a better and safer delivery option in substantial amounts to various skin layers.

Nanocarriers enhance the transdermal bioavailability of resveratrol: In-vitro and in-vivo study

The aim of this study was to develop and assess the potential of nanostructured emulsion carriers for resveratrol topical application. Different compositions of resveratrol-loaded nanostructured emulsions were prepared using different types and amounts of surfactants and oily phases (isopropyl myristate and caproyl 90). The produced nanostructured emulsions were within the nanosized range 23.4-422.2nm with low viscosity range 2.15-17.53cps. The transdermal amount and deposition amount in the skin after 24 applications of resveratrol-loaded nanostructured emulsion were significantly increased about 896.2-fold and 10.2-fold respectively, when compared to the drug-saturated solution-treated group. Nanostructured emulsion containing IPM and low amounts of mixed surfactant of Tween80/Span 20 showed highest permeation capacity. In vivo study showed that the plasma concentration of resveratrol could be maintained at high levels for a long time after topical application of drug-loaded nanostructured emulsion. The histological examination demonstrated that the free drug- and drug-loaded nanostructured emulsion demonstrated considerably less irritation than the standard irritation group (0.8% paraformaldehyde-treated). The residual contents of resveratrol in the tested formulations after 3 months of storage at 25°C and 40°C were more than 99.97±3.90%. The results of present work confirm the high potential of nanostructured emulsion as carriers for drug topical application.

Effect of chitosan coating on microemulsion for effective dermal clotrimazole delivery

Clotrimazole (CTZ) is a broad spectrum antimycotic agent known to be very effective locally for the treatment of fungal skin infections. The aim of this study was to study the effect of chitosan-coated microemulsion (CME) for topical delivery of CTZ and also evaluate its in vitro antifungal efficacy, ex vivo permeation and retention ability on the skin surface. The pseudo-ternary phase diagrams were developed using clove oil as oil phase, Tween 80 and propylene glycol as surfactant and co-surfactant, respectively, and distilled water as aqueous phase. CME was prepared by the drop wise addition of chitosan solution to the optimized microemulsion. Physicochemical parameters (globule size, zeta potential, drug content, viscosity and pH) and in vitro release of CME were studied. The in vitro antifungal efficacy of CME and ME was studied by cup-plate method against Candida albicans. Ex vivo drug permeation study was also carried out in a modified diffusion cell, using rat skin. The developed CME displayed an average globule size less than 50 nm and a positive surface charge, acceptable physico-chemical behavior, and exhibited sustained drug release in in vitro study. In in vitro anti-fungal study, CME showed greater values of zone of inhibition as compared to ME due to its prolonged action as well as fungistatic nature of chitosan. In ex vivo study, CME showed better retention and sustained permeation property than ME due to the mucoadhesive property of chitosan. These results suggest that positively charged CMEs could be used as novel topical formulation for its ability to retain on the skin and its ability to sustain the release of the drug.

Nanostructured lipid carrier mediates effective delivery of methotrexate to induce apoptosis of rheumatoid arthritis via NF-κB and FOXO1

Present study was designed to develop novel nano-structured lipid carriers (NLCs) formulated by lipid mixture and chemical permeation enhancer-based hydrogel for an effective transdermal delivery of methotrexate (MTX). The prepared NLCs were optimized with different preparative variables such as particle size <200 nm, poly-dispersity index (PDI) <0.2, and entrapment efficiency ∼85%. The drug incorporated into NLCs-gel base showed excellent spread ability without any grittiness during rheological behavior and texture profile analysis. The in vitro release showed biphasic release pattern with initial fast release of drug (>50%) in 8h followed by sustained release (up to 85%) by the end of 48thh. NLCs showed greater uptake in human hyper-proliferative keratinocyte cell line (HaCaT). NLCs showed increased expression of inflammatory mediators as well asapoptosis in U937 monocytic cells. The greater expression of pro-apoptotic gene Bim regulated by NF-κB-IkB and FOXO1 is supported by fold regulations calculated for various apoptotic and pro-inflammatory biomarkers carried out by RT-PCR. The immunocytochemistry to detect IL-6 expression and immunofluorescence assay suggested that induced apoptosis occurs in experimentally induced in vitro arthritis model treated with NLCs-MTX. We saw reduced inflammation and triggered apoptosis through NF-κB & FOXO1 pathways induced by MTX loaded NLCs in rheumatoid arthritic cells. In addition, formulated NLCs exhibit better skin permeation with higher permeation flux & enhancement ratio as shown by confocal laser scanning microscopy (CLSM). Moreover, histopathological examinations of skin are suggestive of safety potential of NLCs.