Preparation, evaluation, and NMR characterization of vinpocetine microemulsion for transdermal delivery

Microemulsions strongly promoted the activity of α-bisabolol against different Leishmania species and its skin permeation

This study aimed to develop microemulsions (MEs) containing α-bisabolol for the topical treatment of cutaneous leishmaniasis (CL). Initially, pseudoternary phase diagrams were developed using α-bisabolol as the oil phase, Eumulgin® CO 40 as the surfactant, Polymol® HE as the co-surfactant, and distilled water as the aqueous phase. Two transparent liquid systems (TLS) containing 5% of α-bisabolol were selected and characterized (F5E25 and F5EP25). Next, skin permeation and retention assays were performed using Franz cells. The interaction of the formulation with the stratum corneum (SC) was evaluated using the FTIR technique. The cytotoxicity was evaluated in murine peritoneal macrophages. Finally, the antileishmanial activity of microemulsions was determined in promastigotes and amastigotes of L. amazonensis (strain MHOM/BR/77/LTB 0016). As a result, the selected formulations showed isotropy, nanometric size (below 25 nm), Newtonian behavior and pH ranging from 6.5 to 6.9. The MEs achieved a 2.5-fold increase in the flux and skin-permeated amount of α-bisabolol. ATR-FTIR results showed that microemulsions promoted fluidization and extraction of lipids and proteins of the stratum corneum, increasing the diffusion coefficient and partition coefficient of the drug in the skin. Additionally, F5E25 and F5EP25 showed higher activity against promastigotes (IC50 13.27 and 18.29, respectively) compared to unencapsulated α-bisabolol (IC50 53.8). Furthermore, F5E25 and F5EP25 also showed antileishmanial activity against intracellular amastigotes of L. amazonensis, with IC50 50 times lower than free α-bisabolol and high selectivity index (up to 15). Therefore, the systems obtained are favorable to topical administration, with significant antileishmanial activity against L. amazonensis promastigotes and amastigotes, being a promising system for future in vivo trials.

Overcoming challenges in dermal and transdermal delivery of herbal therapeutics with polymeric microneedles

Natural products are generally preferred medications owing to their low toxicity and irritancy potential. However, a good number of herbal therapeutics (HT) exhibit solubility, permeability and stability issues that eventually affect oral bioavailability. Transdermal administration has been successful in resolving some of these issues which has lead in commercialization of a few herbal transdermal products. Polymeric Microneedles (MNs) has emerged as a promising platform in transdermal delivery of HT that face problems in permeating the skin. Several biocompatible and biodegradable polymers used in the fabrication of MNs have been discussed. MNs have been exploited for cutaneous delivery of HT in management of skin ailments like skin cancer, acne, chronic wounds and hypertrophic scar. Considering the clinical need, MNs are explored for systemic delivery of potent HT for management of diverse disorders like asthma, disorders of central nervous system and nicotine replacement as it obviates first pass metabolism and elicits a quicker onset of therapeutic response. MNs of HT have found good number of aesthetic applications in topical delivery of HT to the skin. Interestingly, MNs have emerged as an attractive option as a minimally invasive diagnostic aid in sampling biomarkers from plants, skin and ocular interstitial fluid. The review updates the progress made by MN technology of HT for multiple therapeutic interventions along with the future challenges. An attempt is made to illustrate the challenging formulation strategies employed in the fabrication of polymeric MNs of HT. Efforts are on to extend the potential applications of polymeric MNs to HT for diverse therapeutic applications.

Liposome and microemulsion loaded with ibuprofen: from preparation to mechanism of drug transport

To compare the difference between liposome (LP) and microemulsion (ME) in delivering ibuprofen (IBU) transdermally and explore relative mechanism. IBU-LP and IBU-ME were prepared by ethanol injection and spontaneous emulsification, respectively. The percutaneous delivery was evaluated using Franz diffusion cells. Fourier transform infra-red spectroscopy (FTIR), differential scanning calorimetry (DSC), activation energy (Ea), and confocal laser scanning microscopy (CLSM) were used to investigate the transdermal mechanism. The particle size and encapsulation efficiency were 228.00 ± 8.60 nm, 86.68 ± 1.43%(w/w) for IBU-LP, and 56.74 ± 7.11 nm, 91.08 ± 3.27%(w/w) for IBU-ME. Percutaneous study showed that formulations enhanced permeation and drug retention in the skin. FTIR and DSC showed that the permeation occurred due to the interaction of the formulations with the lipid bilayer and the protein. The decrease in Ea (1.506 and 0.939 kcal/mol) revealed that the stratum corneum (SC) lipid bilayers were significantly disrupted and this destructive effect of IBU-LP was stronger. IBU-LP was superior to IBU-ME in the aspects of transdermal delivery of IBU.

Investigation of Factors Influencing Formation of Nanoemulsion by Spontaneous Emulsification: Impact on Droplet Size, Polydispersity Index, and Stability

Interest in nanoemulsion technology has increased steadily in recent years for its widespread applications in the delivery of pharmaceuticals, nutraceuticals, and cosmeceuticals. Rational selection of the composition and the preparation method is crucial for developing a stable nanoemulsion system with desired physicochemical characteristics. In the present study, we investigate the influence of intricate factors including composition and preparation conditions that affect characteristic parameters and the stability of the nanoemulsion formation prepared by the spontaneous emulsification method. Octanoic acid, capryol 90, and ethyl oleate were selected to represent oil phases of different carbon–chain lengths. We explored the impact of the addition mode of the oil–S_mix phase and aqueous phase, vortexing time, K_m (surfactant/cosurfactant) ratio, and the replacement of water by buffers of different pH as an aqueous system. The phase behavior study showed that the S_mix phase had a significant impact on the nanoemulsifying ability of the nanoemulsions composed of oil phases of varying carbon-chain lengths. The mode of mixing of the oil–S_mix phase to the aqueous phase markedly influenced the mean droplet size and size distribution of the nanoemulsions composed of oil phases as capryol 90. Vortexing time also impacted the mean droplet size and the stability of the generated nanoemulsion system depending on the varying carbon-chain length of the oil phase. The replacement of the water phase by aqueous buffers of pH 1.2, 5.5, 6.8, and 7.4 has altered the mean droplet size and size distribution of the nanoemulsion system. Further, the K_m ratio also had a significant influence on the formation of the nanoemulsion system. The findings of this investigation are useful in understanding how the formulation composition and process parameters of the spontaneous emulsification technique are responsible for affecting the physicochemical characteristics and stability of the nanoemulsion system composed of oil of varying carbon-chain (C₈-C₁₈) length.

Yeast cell microcarriers for delivery of a model bioactive compound in skin

This study aimed at developing a cell-based encapsulation carrier for topical delivery of bioactives to the skin. The overall objectives were to evaluate affinity of the yeast-cell based carrier to bind to the skin surface following topical application and to quantify controlled release of curcumin as a model bioactive in ex-vivo skin models using a combination of imaging, modeling and analytical measurements. Both porcine skin tissue and clinically obtained human skin biopsies were studied. The results demonstrated that upon incubation with the ex-vivo skin tissues, the cell carriers rapidly bound to the skin surface following topical delivery and provided sustained release of encapsulated curcumin. The microcarrier binding and penetration of curcumin in the dermal compartment also showed to increase with incubation time. The average flux of curcumin in human skin biopsies J_p was 0.89 ± 0.02 μg/cm²/h. These results illustrated the potential of a novel cell-based carrier for high affinity binding to skin surface, efficient encapsulation of a model bioactive and controlled release from the cell carrier to the skin with enhanced permeation to the dermis section. Overall, this study demonstrated a new class of cost-effective carriers for improving delivery of bioactives to the skin and potentially other epithelial tissues.

Recent progress in micro and nano-encapsulation of bioactive derivatives of the Brazilian genus Pterodon

In the last few decades, utilization of medicinal plants by the pharmaceutical industry has led to the identification of many new bioactive compounds. The genus Pterodon, native of the Brazilian Flora, is known for the therapeutic properties attributed to its species, which are widely used in popular medicine for their anti-inflammatory, anti-rheumatic, tonic, and depurative properties. The intrinsic low water solubility of the plant derivatives from the genus, including diterpenes with vouacapane skeletons that are partially associated with the pharmacological activities, impairs the bioavailability of these bioactive compounds. Recent studies have aimed to encapsulate Pterodon products to improve their water solubility, achieve stability, increase their efficacy, and allow clinical applications. The purpose of this paper is to review recent research on the use of nanotechnology for the development of new products from plant derivatives of the Pterodon genus in different types of micro- and nanocarriers. Therapeutic properties of their different products are also presented. Finally, an update about the current and future applications of encapsulated formulations is provided.

Self-Nano-Emulsifying Drug-Delivery Systems: From the Development to the Current Applications and Challenges in Oral Drug Delivery

Approximately one third of newly discovered drug molecules show insufficient water solubility and therefore low oral bio-availability. Self-nano-emulsifying drug-delivery systems (SNEDDSs) are one of the emerging strategies developed to tackle the issues associated with their oral delivery. SNEDDSs are composed of an oil phase, surfactant, and cosurfactant or cosolvent. SNEDDSs characteristics, their ability to dissolve a drug, and in vivo considerations are determinant factors in the choice of SNEDDSs excipients. A SNEDDS formulation can be optimized through phase diagram approach or statistical design of experiments. The characterization of SNEDDSs includes multiple orthogonal methods required to fully control SNEDDS manufacture, stability, and biological fate. Encapsulating a drug in SNEDDSs can lead to increased solubilization, stability in the gastro-intestinal tract, and absorption, resulting in enhanced bio-availability. The transformation of liquid SNEDDSs into solid dosage forms has been shown to increase the stability and patient compliance. Supersaturated, mucus-permeating, and targeted SNEDDSs can be developed to increase efficacy and patient compliance. Self-emulsification approach has been successful in oral drug delivery. The present review gives an insight of SNEDDSs for the oral administration of both lipophilic and hydrophilic compounds from the experimental bench to marketed products.

Evaluation of Bio-Mechanistic Behavior of Liquid Self-Microemulsifying Drug Delivery System in Biorelevant Media

The aim of the study is to mechanistically investigate the drug loci, structural integrity, chemical interactions, and absorption behavior of the liquid self-microemulsifying drug delivery system (SMEDDS). The loci of drug molecules in self-forming microemulsions in biorelevant media (fasted state simulated gastric fluid and fed state simulated intestinal fluid) were investigated by ¹H and ¹³C nuclear magnetic resonance (NMR) spectroscopy. Chemical interactions were observed through attenuated total reflectance spectroscopy (ATR). The structural integrity of self-forming microemulsions in biorelevant media was determined by small angle X-ray scattering (SAXS) and fluorescence resonance energy transfer (FRET). Morphological features of self-forming microemulsion were determined by confocal laser scanning microscopy. In vitro, lipid digestion behavior was evaluated for particle size, zeta potential, free fatty acids (FFA), and drug released through standard protocols. In-house characterizations were determined through standard methodologies. ¹H and ¹³C NMR revealed that drug loci were found in a majority in the oily core region in the self-forming microemulsion. The ATR signifies that no inherent chemical was observed in the liquid SMEDDS and drug-loaded self-microemulsions in the biorelevant media. Structural integrity was well maintained during the dispersive and digestive phases in the gastrointestinal lumen during lipolysis in biorelevant conditions, as revealed by SAXS and FRET. An in vitro digestion study in biorelevant conditions depicts no fluctuations in size and zeta potential with a predominant release of FFA and drug, and was to be revealed physiologically acceptable for clinical applications.

Vinpocetine loaded ultradeformable liposomes as fast dissolving microneedle patch: Tackling treatment challenges of dementia

Vinpocetine (VPN) displays poor bioavailability (~7%) and short half-life (2-3 h) justifying the frequent dosing requirement of currently marketed oral tablets (thrice daily) and thus, posing a great challenge to patient compliance. Present work envisaged to achieve an infusion like delivery through transdermal route so as to tackle aforesaid challenges. With this aim, ultradeformable liposomes (UDL) incorporated fast dissolving microneedle patch (MNP) of VPN was developed and optimized for vesicle size and percent drug entrapment (critical quality attributes, CQA) utilizing the quality by design tool. Fractional factorial design followed by combined D-optimal design were applied to identify critical material attributes and obtain their statistically verified optimum levels (Phospholipon 90G, 15.17 mM; Phospholipon 90H, 4.83 mM; sodium deoxycholate, 15 mol% and Vinpocetine, 5 mol%) showing mean vesicle size of 75.65 nm and mean drug entrapment of 87.44%. An insignificant change in CQA of optimized UDL after incorporation in MNP further represented their physical compatibility with MNP components. In vitro characterization of these microneedles revealed rapid dissolution (~2 min) and good skin penetrability with around 0.684 N axial needle fracture force (ANFF). The safety was ascertained in vitro by exposing HaCaT cells to VPN UDL MNP components. A 94.27% cell viability advocated the safe nature of excipients used in formulation. Ex vivo permeation across full thickness pig ear skin revealed a steady state flux of 11.091 μg/cm²/h via VPN UDL MNP with around 9-fold enhancement when compared to flux value achieved through VPN suspension. In vivo pharmacokinetic and pharmacodynamic study in Sprague Dawley rats showed a 3-fold rise in relative bioavailability and a comparable mean escape latency via UDL MNP as compared to its oral suspension. In addition, half-life of 14 h and MRT of 21 h further confirmed the controlled release behavior of UDL MNP for prolonged period of time. In nutshell, the developed fast dissolving microneedle patch of VPN showed promising results with the prospect of lowering dose as well as dosing frequency for improved patient compliance.

Development of sulconazole-loaded nanoemulsions for enhancement of transdermal permeation and antifungal activity

Background: Sulconazole (SCZ) is a broad-spectrum transdermally administered anti-fungicidal agent. However, the therapeutic effect of SCZ is generally limited by its poor water solubility. This present study aimed to develop and evaluate sulconazole-loaded nanoemulsions (SCZ-NEs) for enhancement of the transdermal permeation and antifungal activity. Methods: A spontaneous titration method was applied to prepare the SCZ-NEs. And the optimized formulation of SCZ-NEs was screened by central composite design (CCD). In addition, the characteristics of the SCZ-NEs were evaluated, including particle size, zeta potential, drug loading (DL%) and encapsulation efficiency (EE%). The morphology of SCZ-NEs was observed by transmission electron microscopy (TEM). Franz diffusion cells were used to evaluate the transdermal permeability of the SCZ-NEs. The antifungal activity of the SCZ-NEs was measured by a zone of inhibition (ZOI) test. Results: The optimized SCZ-NEs possessed a moderate particle size of 52.3±3.8 nm, zeta potential of 23.3±1.2 mV, DL% of 0.47±0.05% and EE% of 87.1±3.2%. The ex vivo skin permeation study verified that the cumulative permeability (Qn) and penetration rate (Js) of the optimized SCZ-NEs were about 1.7-fold higher than that of a commercial reference, miconazole (MCZ) cream and 3-fold higher than that of SCZ-DMSO solution. The optimized SCZ-NEs exhibited zone of inhibition (ZOI) values of 23.5±2.4 and 20.4±2.5 mm against C. albicans and T. rubrum, which were larger compared with these of the MCZ cream and SCZ-DMSO solution. Conclusion: SCZ-NEs were effectively developed to overcome the poor solubility of SCZ, promote SCZ permeation through the skin and improve its antifungal activity. Thus, the SCZ-NEs are a promising percutaneous administration for skin fungal infections induced by C. albicans and T. rubrum.

Formulation and Characterization of Eplerenone Nanoemulsion Liquisolids, An Oral Delivery System with Higher Release Rate and Improved Bioavailability

Because Eplerenone (EPL) is a Biopharmaceutical Classification System (BCS) class-II drug and is prone to extensive liver degradation, it suffers from poor bioavailability after oral administration. This work aimed to prepare liquisolids loaded with EPL-nanoemulsions (EPL-NEs) that have a higher drug release rate and improved bioavailability by the oral route. Based on solubility studies, mixtures of Triacetin (oil) and Kolliphor EL/PEG 400 surfactant/co-surfactant (Smix) in different ratios were used to prepare EPL-NE systems, which were characterized and optimized for droplet size, zeta potential, polydispersity index (PDI), and drug content. Systems were then loaded onto liquisolid formulations and fully evaluated. A liquisolid formulation with better drug release and tableting properties was selected and compared to EPL-NEs and conventional EPL oral tablets in solid-state characterization studies and bioavailability studies in rabbits. Only five NEs prepared at 1:3, 1:2, and 3:1 Smix met the specified optimization criteria. The drug release rate from liquisolids was significantly increased (90% within 45 minutes). EPL-NE also showed significantly improved drug release but with a sustained pattern for four hours. Liquisolid bioavailability reached 2.1 and 1.2 relative to conventional tablets and EPL-NE. This suggests that the EPL-NE liquisolid is a promising oral delivery system with a higher drug release rate, enhanced absorption, decreased liver degradation, and improved bioavailability.

In Vitro Skin Retention and Drug Permeation through Intact and Microneedle Pretreated Skin after Application of Propranolol Loaded Microemulsions

PURPOSE

Topical beta-blockers are efficacious for treating infantile hemangiomas, but no formulations have been specifically optimized for skin delivery. Our objective was to quantify skin concentrations and drug permeation of propranolol (a nonselective beta-blocker) after application of microemulsions to intact and microneedle pretreated skin.

METHODS

Four propranolol-loaded microemulsions were characterized for droplet size, surface charge, conductivity, pH, drug solubility, and drug release. Skin concentrations and drug permeation through skin were quantified using LC-MS. Skin-to-receiver ratios were used to compare the microemulsion formulations to a drug-in-PBS solution.

RESULTS

Propranolol solubility was significantly greater in microemulsions vs PBS. Cumulative drug release from the microemulsions over 24 h ranged from 13 to 26%. Skin concentrations and drug permeation through intact skin was significantly higher from PBS; however, the skin-to-receiver ratios were significantly higher for water-rich microemulsions compared to PBS or surfactant-rich microemulsions. Microneedle pretreatment significantly increased skin concentrations for all formulations. Skin-to-receiver ratios significantly increased after microneedle pretreatment for surfactant-rich microemulsions.

CONCLUSIONS

Microemulsion formulation can be altered to elicit different drug delivery profiles through MN-treated skin. This could be advantageous for maximizing local skin drug concentrations and improving dosing schedules for infantile hemangioma treatment.

Enhancement of Antibacterial Activity of Orange Oil in Pectin Thin Film by Microemulsion

The purpose of this study was to prepare orange oil microemulsion (ME) and to investigate the antimicrobial activity of film containing orange oil ME. First, surfactants and co-surfactants were screened on their efficiency to form ME using pseudo-ternary phase diagrams. The influences of surfactant and co-surfactant mass ratios were studied and optimized ME-loaded-films were prepared. Then, films containing orange oil ME were characterized by SEM and texture analyzer, and then evaluated for antimicrobial activity against Staphylococcus aureus and Propionibacterium acnes using an agar disc diffusion method. The results showed that Tween 80 as surfactant and propylene glycol as co-surfactant at a 1:1 ratio possessed the maximum ME area. Three ME formulations of ME 20, ME 25, and ME 30, which consisted of 20, 25, and 30% w/v of orange oil were prepared, respectively. All ME formulations showed particle sizes of about 60.26⁻80.00 nm, with broad a polydispersity index of 0.42. The orange oil ME films exhibited higher elastic values than the control. The diameters of inhibition zones for FME 20, FME 25, and FME 30 against P. acnes were 13.64, 15.18, and 16.10 mm, respectively. Only the FME 30 had an antimicrobial activity against S. aureus with 8.32 mm of inhibition zone. Contrarily, the control film had no antimicrobial activity against both bacteria. In conclusion, the present study found that the antibacterial activity of orange oil in pectin thin film could be enhanced by preparing orange oil as an ME before loading into pectin thin film.

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.

Topical Nano and Microemulsions for Skin Delivery

Nanosystems such as microemulsions (ME) and nanoemulsions (NE) offer considerable opportunities for targeted drug delivery to and via the skin. ME and NE are stable colloidal systems composed of oil and water, stabilised by a mixture of surfactants and cosurfactants, that have received particular interest as topical skin delivery systems. There is considerable scope to manipulate the formulation components and characteristics to achieve optimal bioavailability and minimal skin irritancy. This includes the incorporation of established chemical penetration enhancers to fluidize the stratum corneum lipid bilayers, thus reducing the primary skin barrier and increasing permeation. This review discusses nanosystems with utility in skin delivery and focuses on the composition and characterization of ME and NE for topical and transdermal delivery. The mechanism of skin delivery across the stratum corneum and via hair follicles is reviewed with particular focus on the influence of formulation.

Optimizing the dermal accumulation of a tazarotene microemulsion using skin deposition modeling

CONTEXT

It is well known that microemulsions are mainly utilized for their transdermal rather than their dermal drug delivery potential due to their low viscosity, and the presence of penetration enhancing surfactants and co-surfactants.

OBJECTIVE

Applying quality by design (QbD) principles, a tazarotene microemulsion formulation for local skin delivery was optimized by creating a control space.

MATERIALS AND METHODS

Critical formulation factors (CFF) were oil, surfactant/co-surfactant (SAA/CoS), and water percentages. Critical quality attributes (CQA) were globular size, microemulsion viscosity, tazarotene skin deposition, permeation, and local accumulation efficiency index.

RESULTS AND DISCUSSION

Increasing oil percentage increased globular size, while the opposite occurred regarding SAA/CoS, (p = 0.001). Microemulsion viscosity was reduced by increasing oil and water percentages (p < 0.05), due to the inherent high viscosity of the utilized SAA/CoS. Drug deposition in the skin was reduced by increasing SAA/CoS due to the increased hydrophilicity and viscosity of the system, but increased by increasing water due to hydration effect (p = 0.009). Models with very good fit were generated, predicting the effect of CFF on globular size, microemulsion viscosity, and drug deposition. A combination of 40% oil and 45% SAA/CoS showed the maximum drug deposition of 75.1%. Clinical skin irritation study showed that the aforementioned formula was safe for topical use.

CONCLUSION

This article suggests that applying QbD tools such as experimental design is an efficient tool for drug product design.

Microemulsion-based antifungal gel delivery to nail for the treatment of onychomycosis: formulation, optimization, and efficacy studies

Onychomycosis is the most common nail disease affecting nail plate and nail bed. Onychomycosis causes onycholysis which creates cavity between the nail plate and nail bed, where drug formulations could be applied, providing a direct contact of drug with the nail bed facilitating drug delivery on the infected area. The purpose of the present study was to design and evaluate the potential of microemulsion-based gel as colloidal carrier for itraconazole for delivery into onycholytic nails for effective treatment of onychomycosis. Itraconazole-loaded microemulsions were prepared and optimized using D-optimal design. The microemulsion containing 6.24 % oil, 36 % Smix, and 57.76 % water was selected as the optimized batch (MEI). The globule size and drug loading of the optimized batch were 48.2 nm and 12.13 mg/ml, respectively. Diffused reflectance FTIR studies were performed to study drug-excipient incompatibility. Ex vivo permeation studies were carried out using bovine hoof and human cadaver skin as models for nail plate and nail bed, respectively. Microemulsion-based itraconazole gel (MBGI) showed better penetration and retention in human skin as well as bovine hoof as compared to commercial preparation (market formulation, MFI). The cumulative amount of itraconazole permeated from the MBGI after 12 h was 73.39 ± 3.55 μg cm(-2) which was 1.8 times more than MF. MBGI showed significantly higher ex vivo antifungal activity (P < 0.05) against Candida albicans and Trichophyton rubrum when compared to MFI. Stability studies showed that MBGI was stable at refrigeration and room temperature for 3 months. It was concluded that drug-loaded gel could be a promising formulation for effective treatment of onychomycosis.

Microemulsion based on Pterodon emarginatus oil and its anti-inflammatory potential

This article reports the development of a pharmaceutical product containing vegetable actives from a Brazilian medicinal plant. The possibility of forming a microemulsion using Pterodon emarginatus ("sucupira") oil was evaluated and the anti-inflammatory potential of this microemulsion was also examined. A formulation was developed using P. emarginatus oil, a mixture of ethoxylated Castor Oil (Ultramone(r) R-540/propylene glycol 2:1) (surfactant/cosurfactant) and distilled water at a ratio of 10:15:75, respectively. The microemulsion which was selected was then subjected to the preliminary stability test and analyzed in terms of average diameter of droplets, pH, zeta potential, and polydispersity index, on the 1st, 7th, 15th, and 30th days after preparation and stored at different temperatures (5 ± 2 °C, 25 ± 2 °C, and 40 ± 2 °C). The anti-inflammatory in vivo activity of both oil and formulation were evaluated, using the experimental model of croton oil-induced ear edema. The preliminary stability test showed that the microemulsion stored at 5 and 25 °C retained its original features throughout the 30-day period. The anti-inflammatory potential of both oil and formulation was shown to be statistically significant (p < 0.001), when compared to the control group, however, the microemulsion proved to be more effective (p < 0.05) than the oil when applied directly to the ear.

Overcoming the cutaneous barrier with microemulsions

Microemulsions are fluid and isotropic formulations that have been widely studied as delivery systems for a variety of routes, including the skin. In spite of what the name suggests, microemulsions are nanocarriers, and their use as topical delivery systems derives from their multiple advantages compared to other dermatological formulations, such as ease of preparation, thermodynamic stability and penetration-enhancing properties. Composition, charge and internal structure have been reported as determinant factors for the modulation of drug release and cutaneous and transdermal transport. This manuscript aims at reviewing how these and other characteristics affect delivery and make microemulsions appealing for topical and transdermal administration, as well as how they can be modulated during the formulation design to improve the potential and efficacy of the final system.

Microemulsion-based gel of terbinafine for the treatment of onychomycosis: optimization of formulation using D-optimal design

The aim of the present investigation was to evaluate microemulsion as a vehicle for dermal drug delivery and to develop microemulsion-based gel of terbinafine for the treatment of onychomycosis. D-optimal mixture experimental design was adopted to optimize the amount of oil (X(1)), Smix (mixture of surfactant and cosurfactant; X(2)) and water (X(3)) in the microemulsion. The formulations were assessed for globule size (in nanometers; Y(1)) and solubility of drug in microemulsion (in milligrams per milliliter; Y(2)). The microemulsion containing 5.75% oil, 53.75% surfactant-cosurfactant mixture and 40.5% water was selected as the optimized batch. The globule size and solubility of the optimized batch were 18.14 nm and 43.71 mg/ml, respectively. Transmission electron microscopy showed that globules were spherical in shape. Drug containing microemulsion was converted into gel employing 0.75% w/w carbopol 934P. The optimized gel showed better penetration and retention in the human cadaver skin as compared to the commercial cream. The cumulative amount of terbinafine permeated after 12 h was 244.65 ± 18.43 μg cm(-2) which was three times more than the selected commercial cream. Terbinafine microemulsion in the gel form showed better activity against Candida albicans and Trichophyton rubrum than the commercial cream. It was concluded that drug-loaded gel could be a promising formulation for effective treatment of onychomycosis.

Permeation and skin retention of quercetin from microemulsions containing Transcutol® P

A microemulsion for the cutaneous release of quercetin was prepared. An aqueous phase, containing 40% Transcutol® P as solubilizing agent and permeation enhancer, was emulsified with Labrafil® as oil phase and Labrasol®/Capryol™ 90 as Solvent/Co-solvent. Quercetin was dissolved in the microemulsion at the concentration of 1%. Ternary phase diagrams were generated to determine the optimal concentration of each excipient composing the microemulsion. The physicochemical properties of the microemulsion, such as pH, viscosity, refractive index, and particle size distribution were determined. The microemulsion was stable for 12 months at the storing conditions of 25.0 ± 1.0°C. The in vitro quercetin permeability into and through the abdominal hairless pig skin was determined by vertical Franz's cells. Quercetin showed hardly any permeability through the skin when dissolved in water- and Transcutol® P-free media, whereas a remarkable increase in cutaneous permeability was observed when quercetin was formulated in the microemulsion or when simply dissolved in Transcutol® P. These two last formulations are those showing the lower skin retention.

Investigation of microemulsion microstructures and their relationship to transdermal permeation of model drugs: ketoprofen, lidocaine, and caffeine

In this study, microemulsion microstructures, key formulation variables, and their relationship to drug transdermal permeation enhancement were investigated. A microemulsion system with high water soluble capacity was developed, using isopropyl myristate, Labrasol, and Cremophor EL as oil, surfactant, and co-surfactant, respectively. The microstructures of the microemulsions were characterized by a combination of techniques including electrical conductivity measurement (EC), differential scanning calorimetry (DSC), electro-analytical cyclic voltammetry (CV), dynamic light scattering (DLS). Three microemulsion formulations with the model drugs at water contents of 20%, 40%, and 70% representing the microstructures of W/O, Bi-continuous, and O/W were prepared along the water dilution line of oil to surfactant ratio of 1/9. Skin permeation of hydrophobic and hydrophilic model drugs, ketoprofen, lidocaine, and caffeine in the microemulsion formulations was studied using Franz-cells and dermatomed porcine skin. Permeation of all drugs from microemulsions was enhanced significantly compared with the control propylene glycol formulation. The drug permeation flux and the cumulative permeation amount after 24h increased with water content in the microemulsions, thus correlated to the formulation microstructures of W/O, Bi-continuous, and O/W. The permeation of lipophilic drugs ketoprofen and lidocaine increased with water content in a more pronounced manner, which seemed to follow an exponential growth trend, while the permeation of hydrophilic drug caffeine appeared to increase linearly. Additionally, at the same water content, increasing oil content led to higher ketoprofen permeation.

Novel dithranol phospholipid microemulsion for topical application: development, characterization and percutaneous absorption studies

The objective of this study was to develop and characterize a novel dithranol-containing phospholipid microemulsion systems for enhanced skin permeation and retention. Based on the solubility of dithranol, the selected oils were isopropyl myristate (IPM) and tocopherol acetate (TA), and the surfactants were Tween 80 (T80) and Tween 20 (T20). The ratios of cosurfactants comprising of phospholipids and ethanol (1 : 10) and surfactant to co-surfactant (1 : 1 and 2.75 : 1) were fixed for the phase diagram construction. Selected microemulsions were evaluated for globule size, zeta potential, viscosity, refractive index, per cent transmittance, stability (freeze thaw and centrifugation), ex vivo skin permeation and retention. The microemulsion systems composed of IPM and T80 with mean particle diameter of 72.8 nm showed maximum skin permeation (82.23%), skin permeation flux (0.281 mg/cm²/h) along with skin retention (8.31%) vis-à-vis systems containing TA and T20. The results suggest that the developed novel lecithinized microemulsion systems have a promising potential for the improved topical delivery of dithranol.

Novel sugar esters proniosomes for transdermal delivery of vinpocetine: preclinical and clinical studies

Vinpocetine (Vin) existing oral formulations suffer poor bioavailability (∼7%) since Vin undergoes a marked first-pass effect (∼75%) and its absorption is dissolution rate-limited. In this study, a novel sustained release proniosomal system was designed using sugar esters (SEs) as non-ionic surfactants in which proniosomes were converted to niosomes upon skin water hydration following topical application under occlusive conditions. Different in vitro aspects (encapsulation efficiency, vesicle size and shape, effect of occlusion, in vitro release, skin permeation and stability) were studied leading to an optimized formula that was assessed clinically for transdermal pharmacokinetics and skin irritation. All formulae exhibited high entrapment efficiencies, regardless of the surfactant HLB. Vesicle size analysis showed that all vesicles were in the range from 0.63 μm to 2.52 μm which favored efficient transdermal delivery. The extent of drug permeation through the skin from the optimized formula--containing laurate SE with shorter fatty acid chain length and high HLB--was quite high (91%) after 48 h under occlusive conditions. The extent of absorption of Vin from proniosomes was larger when compared to the oral tablet with a relative bioavailability (F(rel)) of 206%. Histopathological evaluation revealed only moderate skin irritation when using SEs compared to skin inflammation when using Tween 80. Sugar esters proniosomes may be a promising carrier for vinpocetine, especially due to their simple scaling up and their ability to control drug release.

Nanocarrier for the transdermal delivery of an antiparkinsonian drug

The purpose of the present study was to investigate the potential of nanoemulsions as nanodrug carrier systems for the percutaneous delivery of ropinirole. Nanoemulsions comprised Capryol 90 as the oil phase, Tween 20 as the surfactant, Carbitol as the cosurfactant, and water as an external phase. The effects of composition of nanoemulsion, including the ratio of surfactant and cosurfactant (Smix) and their concentration on skin permeation, were evaluated. All the prepared nanoemulsions showed a significant increase in permeation parameters such as steady state flux (Jss) and permeability coefficient (Kp) when compared to the control (p<0.01). Nanoemulsion composition (NEL3) comprising ropinirole (0.5% w/w), Capryol 90 (5% w/w), Smix 2:1 (35% w/w), and water (59.5% w/w) showed the highest flux (51.81+/-5.03 microg/cm2/h) and was selected for formulation into nanoemulsion gel. The gel was further optimized with respect to oil concentration (Capryol 90), polymer concentration (Carbopol), and drug content by employing the Box-Behnken design, which statistically evaluated the effects of these components on ropinirole permeation. Oil and polymer concentrations were found to have a negative influence on permeation, while the drug content had a positive effect. Nanoemulsion gel showed a 7.5-fold increase in skin permeation rate when compared to the conventional hydrogel. In conclusion, the results of the present investigation suggested a promising role of nanoemulsions in enhancing the transdermal permeation of ropinirole.

Formulation optimization and in situ absorption in rat intestinal tract of quercetin-loaded microemulsion

A new microemulsion system has been developed to increase the solubility and oral absorption of quercetin, a poorly water-soluble drug. The formulation of quercetin-loaded microemulsion was optimized by a simplex lattice experiment design. The optimized microemulsion formulation consisted of oil (7%, w/w), surfactant (48%, w/w), and cosurfactant (45%, w/w). Under this condition, the mean droplet diameter of microemulsion was 38.9 nm and solubility of quercetin in the microemulsion was 4.138 mg/ml. The in situ absorption property of quercetin-loaded microemulsion in rat intestine was studied and the results showed there was significant difference in absorption parameters such as K(a), t(1/2) and uptake percentages between microemulsion and micelle solution containing quercetin. The study on absorption percentage in different regions of rat intestine attested that the colon had the best permeability, followed by ileum, duodenum in order. It can be concluded that microemulsion can improve the solubility and oral absorption of quercetin, a poorly water-soluble drug.

Oral microemulsions of paclitaxel: in situ and pharmacokinetic studies

The overall goal of this study was to develop cremophor-free oral microemulsions of paclitaxel (PAC) to enhance its permeability and oral absorption. The mechanism of this enhancement, as well as characteristics of the microemulsions relevant to the increase in permeability and absorption of the low solubility, low permeability PAC was investigated. Phase diagrams were used to determine the macroscopic phase behavior of the microemulsions and to compare the efficiency of different surfactant-oil mixtures to incorporate water. The microemulsion region on the phase diagrams utilizing surfactant-myvacet oil combinations was in decreasing order: lecithin: butanol: myvacet oil (LBM, 48.5%)>centromix CPS: 1-butanol: myvacet oil (CPS, 45.15%)>capmul MCM: polysorbate 80: myvacet oil (CPM, 27.6%)>capryol 90: polysorbate 80: myvacet oil (CP-P80, 23.9%)>capmul: myvacet oil (CM, 20%). Oil-in-water (o/w) microemulsions had larger droplet sizes (687-1010 nm) than the water-in-oil (w/o) microemulsions (272-363 nm) when measured using a Zetasizer nano series particle size analyzer. Utilizing nuclear magnetic resonance spectroscopy (NMR), the self-diffusion coefficient (D) of PAC in CM, LBM and CPM containing 10% of deuterium oxide (D(2)O) was 2.24x10(-11), 1.97x10(-11) and 0.51x10(-11) m(2)/s, respectively. These values indicate the faster molecular mobility of PAC in the two w/o microemulsions (CM and LBM) than the o/w microemulsion--CPM. The in situ permeability of PAC through male CD-IGS rat intestine was 3- and 11-fold higher from LBM and CM, respectively, than that from the control clinical formulation, Taxol (CE, cremophor: ethanol) in a single pass perfusion study. PAC permeability was significantly increased in the presence of the pgp/CYP3A4 inhibitor cyclosporine A (CsA). This enhancement may be attributed to the pgp inhibitory effect of the surfactants, oil and/or the membrane perturbation effect of the surfactants. The oral disposition of PAC in CM, LBM and CPM compared to CE was studied in male CD-IGS rats after a single oral dose (20 mg/kg). The area-under-the-curve of PAC in CM was significantly larger than LBM, CPM and CE. Oral microemulsions of PAC were developed that increased both the permeability and AUC of PAC as compared to CE.