Physicochemical investigations of microemulsification of eucalyptus oil and water using mixed surfactants (AOT+Brij-35) and butanol

Influence of the Dispersion Medium and Cryoprotectants on the Physico-Chemical Features of Gliadin- and Zein-Based Nanoparticles

The evaluation of the physico-chemical features of nanocarriers is fundamental because the modulation of these parameters can influence their biological and in vivo fate. This work investigated the feasibility of saline, 5% w/v glucose and phosphate-buffered saline solution, as polar media for the development of nanoparticles made up of two vegetal proteins, zein from corn and gliadin from wheat, respectively. The physico-chemical features of the various systems were evaluated using dynamic and multiple light scattering techniques, and the results demonstrate that the 5% w/v glucose solution is a feasible medium to be used for their development. Moreover, the best formulations were characterized by the aforementioned techniques following the freeze-drying procedure. The aggregation of the zein nanoparticles prepared in water or glucose solution was prevented by using various cryoprotectants. Mannose confirmed its crucial role in the cryopreservation of the gliadin nanosystems prepared in both water and glucose solution. Sucrose and glucose emerged as additional useful excipients when they were added to gliadin nanoparticles prepared in a 5% glucose solution. Specifically, their protective effect was in the following order: mannose > sucrose > glucose. The results obtained when using specific aqueous media and cryoprotectants permitted us to develop stable zein or gliadin nanoparticles as suspension or freeze-dried formulations.

Fully dilutable Thymus vulgaris essential oil:acetic or propionic acid microemulsions are potent fruit disinfecting solutions

The aim of this study was to evaluate the effect of acetic (AA) or propionic (PA) acid as a cosurfactant on the microemulsion (ME) characteristics of Thymus vulgaris essential oil (TVO). The results showed that addition of propylene glycol to TVO/AA or PA:T80/water MEs gave dilutable systems with particles ~59 nm in diameter. Plain TVO showed the highest antimicrobial activity against E. coli, S. aureus, and S. typhi in in vitro antimicrobial tests, followed closely by AA/PA-MEs. The antimicrobial activity of AA/PA-MEs used as a washing solution on cucumber and strawberry samples was remarkably greater than those of free TVO, TVO nanoemulsions, and chlorhexidine solutions against E. coli and S. aureus. The sensory properties of the samples were not changed by the use of AA/PA-MEs at 0.05 or 0.1% TVO. The results introduce dilutable TVO:AA/PA-MEs for incorporation of TVO in aqueous systems for use as a fruit/vegetable disinfecting agent.

Topical Delivery of Meloxicam using Liposome and Microemulsion Formulation Approaches

The aim of this study is to develop, characterize and compare conventional liposome, deformable liposome (transfersome) and microemulsion formulations as potential topical delivery systems for meloxicam. Liposomes were characterized in terms of vesicle size, zeta potential and entrapment efficiency. For microemulsions, particle size, electrical conductivity and viscosity studies were performed to assess the structure of the investigated systems. An ex vivo skin permeation study has been conducted to compare these formulations. The dermal and transdermal delivery of meloxicam using these formulations can be a promising alternative to conventional oral delivery of non-steroidal anti-inflammatory drugs (NSAIDs) with enhanced local and systemic onset of action and reduced side effects.

Fourth-Generation Antibiotic Gatifloxacin Encapsulated by Microemulsions: Structural and Probing Dynamics

To overcome the increased disease rate, utilization of the versatile broad spectrum antibiotic drugs in controlled drug-delivery systems has been a challenging and complex consignment. However, with the development of microemulsion (μE)-based formulations, drugs can be effectively encapsulated and transferred to the target source. Herein, two biocompatible oil-in-water (o/w) μE formulations comprising clove oil/Tween 20/ethylene glycol/water (formulation A) and clove oil/Tween 20/1-butanol/water (formulation B) were developed for encapsulating the gatifloxacin (GTF), a fourth-generation antibiotic. The pseudoternary phase diagrams were mapped at a constant surfactant/co-surfactant (1:1) ratio to bound the existence of a monophasic isotropic region for as-formulated μEs. Multiple complementary characterization techniques, namely, conductivity (σ), viscosity (η), and optical microscopy analyses, were used to study the gradual changes that occurred in the microstructure of the as-formulated μEs, indicating the presence of a percolation transformation to a bicontinuous permeate flow. GTF showed good solubility, 3.2 wt % at pH 6.2 and 4.0 wt % at pH 6.8, in optimum μE of formulation A and formulation B, respectively. Each loaded μE formulation showed long-term stability over 8 months of storage. Moreover, no observable aggregation of GTF was found, as revealed by scanning transmission electron microscopy and peak-to-peak correlation of IR analysis, indicating the stability of GTF inside the formulation. The average particle size of each μE, measured by dynamic light scattering, increased upon loading GTF, intending the accretion of drug in the interfacial layers of microdomains. Likewise, fluorescence probing sense an interfacial hydrophobic environment to GTF molecules in any of the examined formulations, which may be of significant interest for understanding the kinetics of drug release.

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.

Food-grade Water in Oil Microemulsion as a Potential Approach for Tea Polyphenols Encapsulation

Food-grade water in oil (W/O) microemulsions were developed and characterized in order to use them as potential tea polyphenols (TP) carriers. The physicochemical characteristics of microemulsions (TP-loaded and blank microemulsions) were investigated by rheological measurements, differential scanning calorimetry (DSC), dynamic light scattering (DLS) and 1H nuclear magnetic resonance (1H NMR). The thermal behavior of the microemulsion system implied that the water molecules were competitively bound. Chemical shift patterns for all samples were not sensitive to the addition of TP. The microscopic images showed that both the non-loaded and the TP-loaded microemulsions had a spherical shape, in particular the TP-loaded microemulsions had a specific core-shell morphology. TP solubilized in the microemulsions was much more stable than that dissolved in water solution. The release process of TP in water solution was faster than that of microemulsions.

Encapsulation of Antibiotic Levofloxacin in Biocompatible Microemulsion Formulation: Insights from Microstructure Analysis

Microemulsions (μEs) are unique systems that offer exciting perspectives in biophysical research for mimicing biomembranes at the molecular level. In the present study, biocompatible μE formulation of a new oil-in-water (o/w) system comprising clove oil/Tween 20/2-propanol/water was accomplished for encapsulating an antibiotic, levofloxacin (LVF). The pseudoternary phase diagram was delineated at a constant cosurfactant/surfactant (2:1) ratio to meet the economic feasibility. The gradual changes occurring in the microstructure of the as-formulated four-component μEs were explored via multiple complementary characterization techniques. The results of electrical conductivity (σ), viscosity (η), and optical microscopic measurements suggested the existence of a percolation transition to a bicontinuous structure in the microregions of the as-formulated μE. LVF displayed a high solubility (5.0 wt %) at the pH of 6.9 in an optimum μE formulation comprising 2-propanol (36.4%), Tween 20 (18.2%), clove oil (20.7%), and water (24.7%). The LVF-loaded μE composition showed long-term stability for over 6 months of storage. Fourier transform IR analysis showed that LVF was stable inside the μE formulation, indicating the absence of any possible aggregation of LVF. Dynamic light scattering revealed that the average particle size of drug-free μE (64.5 ± 3.4 nm) increases to 129.7 ± 5.8 nm upon loading of LVF, suggesting the accumulation of LVF in the interfacial layers of the micelles. Moreover, fluorescence measurements indicated that LVF might be localized in the interfacial film of μE system, which may result in a controlled release of drug.

Mixed surfactant based (SNEDDS) self-nanoemulsifying drug delivery system presenting efavirenz for enhancement of oral bioavailability

This study aims to develop a self-nanoemulsifying drug delivery system (SNEDDS) based on non-ionic surfactant mixtures to improve the oral bioavailability of efavirenz (EFZ) categorized as a class II according to the BCS, for HIV- therapy. The result of solubility studies of EFZ in various excipients utilized for construction of the pseudo ternary phase diagram containing surfactant mixtures. Surfactants in 1:1 combination are used with different co-surfactants in different ratio to delineate the area of monophasic region of the pseudo ternary phase diagram. Different accelerated physical stability studies and self-emulsification assessment were performed on the formulations. The formulations clearing the above studies are considered for percentage transmittance and turbidity analysis. The globule size distributions of post diluted SNEDDS having percentage transmittance above 90 were estimated. The TEM analysis of two optimized post diluted SNEDDS formulations further confirm the size in nanometric range (below 50nm). FT-IR studies showed the retention of the characteristic peaks of EFZ in the preconcentrate. The in vitro dissolution profile of SNEDDS established advantages of SNEDDS over plain drug as more than 80% drug was released within 30min in case of optimized SNEDDS while it was approximately 18.3% in the case of plain drug powder. Pharmacokinetic parameters were calculated after performing the in vivo studies of best optimized formulation in rats. The Pharmacokinetic data reveal a 2.63 fold increase in AUC(0-∞) in comparison to plain EFZ suspension. The designed delivery system showed the faith in generating an effective formulation of EFZ for HIV treatment.

Food grade microemulsion systems: canola oil/lecithin:n-propanol/water

In this study, the capability of a natural surfactant, lecithin, and the influence of ionic strength, pH, and temperature on some properties of a food grade microemulsion system were evaluated. For this purpose, the pseudoternary phase diagrams of canola oil/lecithin:n-propanol/water microemulsions in the presence of different salts (NaCl and CaCl2), ionic strengths, pHs, and temperatures were constructed. Our findings showed that the presence of salts slightly increased the W/O areas on the phase diagrams, whereas pH variation was not effective on the microemulsion formation. The expansion of microemulsion areas with temperature indicated the greater triglycerides solubilization capacity of lecithin based microemulsions at higher temperatures. These findings revealed the efficiency of lecithin-based microemulsion system for solubilization of triglycerides which can potentially be used for extraction of edible vegetable oils particularly canola oil.

Physicochemical characterization and thermodynamic studies of nanoemulsion-based transdermal delivery system for fullerene

Fullerene nanoemulsions were formulated in palm kernel oil esters stabilized by low amount of mixed nonionic surfactants. Pseudoternary phase diagrams were established in the colloidal system of PKOEs/Tween 80 : Span 80/water incorporated with fullerene as antioxidant. Preformulation was subjected to combination of high and low energy emulsification methods and the physicochemical characteristics of fullerene nanoemulsions were analyzed using electroacoustic spectrometer. Oil-in-water (O/W) nanoemulsions with particle sizes in the range of 70–160 nm were formed. The rheological characteristics of colloidal systems exhibited shear thinning behavior which fitted well into the power law model. The effect of xanthan gum (0.2–1.0%, w/w) and beeswax (1–3%, w/w) in the estimation of thermodynamics was further studied. From the energetic parameters calculated for the viscous flow, a moderate energy barrier for transport process was observed. Thermodynamic study showed that the enthalpy was positive in all xanthan gum and beeswax concentrations indicating that the formation of nanoemulsions could be endothermic in nature. Fullerene nanoemulsions with 0.6% or higher xanthan gum content were found to be stable against creaming and flocculation when exposed to extreme environmental conditions.

Viscosity and Percolative Phenomena in AOT based Microemulsions

Present work includes experimental studies related to the viscosimetric behaviour of microemulsions that consist of three compounds: isooctane (organic phase), water (aqueous phase) and Aerosol OT (surfactant). The effect of the microemulsion composition, based on the ω parameter value, and the effect caused by the temperature have been analysed in this work. In relation to the influence of temperature and the use of microemulsions in different processes, one important characteristic of this kind of systems (the percolation phenomenon) must be taken into account in the discussion of the experimental results.

Properties of Microemulsions with Mixed Nonionic Surfactants and Mint Oil

In this study we used electrical conductivity, dynamic viscosity, dynamic light scattering, and small angle X-ray scattering for the characterization of the water + propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/peppermint oil microemulsion systems. The maximum water solubilization in the peppermint oil was found to be dependent on the surfactants mixing ratio (w/w). A Static percolation threshold was determined. The activation energy of conductive flow depends on the surfactants mixing ratio. The hydrodynamic diameter of the diluted microemulsions decreases with the increase in temperature. The periodicity d of the microemulsions increases with the increase in the aqueous phase content. The correlation length ξ increases and decreases with the increase in the aqueous phase content indicating the onset of structural transitions.

Microemulsions with Mixed Nonionic Surfactants and Isopropylmyristate

Water/propylene glycol/sucrose laurate/ethoxylated mono-di-glyceride/isopropylmyristate microemulsion systems were formulated and investigated using electrical conductivity and small angle X-ray scattering. The solubilization capacity of water in oil is dependent on the surfactants mixing ratio (w/w). The free energy of solubilization (ΔGo s) values for water-in-oil microemulsions were calculated and found to decrease with water content in the water-in-oil microemulsions, they decreased with increasing ethoxylated mono-di-glyceride content in the mixed surfactants. The activation energy of conductive flow was estimated and a percolation phenomenon was revealed in these systems. Small angle X-ray scattering results indicate that the periodicity increases linearly with the increase in the water volume fraction in these microemulsions. The correlation length increases with the increase in the water volume fraction to a certain value then decreases.

Microstructure, morphology, and ultrafast dynamics of a novel edible microemulsion

An edible microemulsion (ME) composed of Tween 80/butyl lactate/isopropyl myristate (IPM)/water has been formulated. Pseudoternary phase diagram of the system contains a large single isotropic region. The phase behavior of the system is also studied at low pH (2.6) and in 0.9% NaCl solution. Conductivity, viscosity, ultrasonic velocity, and compressibility studies find consistent results in the structural transition (from water-in-oil (w/o) to bicontinuous, and from bicontinuous to oil-in-water (o/w)) behavior of the ME. Dynamic light scattering studies reveal the size of the MEs. The absorption and steady state emission spectra of 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM) successfully probe the polarity of the ME at its solvation shell and shows the efficacy of hosting model drug molecules. The rotational anisotropy of the dye has been studied to ascertain the geometrical restriction of the probe molecule. Picosecond-resolved fluorescence spectroscopy applies well to study the relaxation dynamics of water in the solvation shell of the MEs. The study finds strong correlation in the relaxation dynamics of water with the structure of host assembly and offers an edible ME system which could act as a potential drug delivery system and nontoxic nanotemplate for other applications.

Microemulsions as vehicles for topical administration of voriconazole: formulation and in vitro evaluation

This work was undertaken to investigate microemulsion (ME) as a topical delivery system for the poorly water-soluble voriconazole. Different ME components were selected for the preparation of plain ME systems with suitable rheological properties for topical use. Two permeation enhancers were incorporated, namely sodium deoxycholate or oleic acid. Drug-loaded MEs were evaluated for their physical appearance, pH, rheological properties and in vitro permeation studies using guinea pig skin. MEs based on polyoxyethylene(10)oleyl ether (Brij 97) as the surfactant showed pseudoplastic flow with thixotropic behavior and were loaded with voriconazole. Jojoba oil-based MEs successfully prolonged voriconazole release up to 4 h. No significant changes in physical or rheological properties were recorded on storage for 12 months at ambient conditions. The presence of permeation enhancers favored transdermal rather than dermal delivery. Sodium deoxycholate was more effective than oleic acid for enhancing the voriconazole permeation. Voriconazole-loaded MEs, with and without enhancers, showed significantly better antifungal activity against Candida albicans than voriconazole supersaturated solution. In conclusion, the studied ME formulae could be promising vehicles for topical delivery of voriconazole.

Tween-embedded microemulsions--physicochemical and spectroscopic analysis for antitubercular drugs

The microemulsion composed of oleic acid, phosphate buffer, ethanol, and Tween (20, 40, 60, and 80) has been investigated in the presence of antitubercular drugs of extremely different solubilities, viz. isoniazid (INH), pyrazinamide (PZA), and rifampicin (RIF). The phase behavior showing the realm of existence of microemulsion has been delineated at constant surfactant/co-surfactant ratio (K (m) = 0.55) with maximum isotropic region resulting in the case of Tween 80. The changes in the microstructure of Tween 80-based microemulsion in the presence of anti-TB drugs have been established using conductivty (sigma) and viscosity (eta) behavior. The optical microscopic images of the system help in understanding the effect of dilution and presence of drug on the structure of microemulsion. Partition coefficient, particle size analysis, and spectroscopic studies (UV-visible, Fourier transform infrared, and 1H NMR) have been performed to evaluate the location of a drug in the colloidal formulation. To compare the release of RIF, PZA, and INH from Tween 80 formulation, the dissolution studies have been carried out. It shows that the release of drugs follow the order INH>PZA>RIF. The kinetics of the release of drug has been analyzed using the Korsmeyer and Peppas equation. The results have given a fair success to predict that the release of PZA and INH from Tween 80 microemulsion is non-Fickian, whereas RIF is found to follow a Fickian mechanism.

Formulation and characterization of microemulsions based on mixed nonionic surfactants and peppermint oil

Water/sucrose laurate/ethoxylated mono-di-glyceride/ethanol/peppermint oil microemulsion systems were formulated and characterized using electrical conductivity, dynamic viscosity, nuclear magnetic resonance, dynamic light scattering, small angle X-ray scattering and cryogenic transmission electron microscopy. The solubilization capacity of water in the oil is dependent on the surfactants and ethanol/oil mixing ratios (w/w). Static percolation phenomena were observed in these systems, and the water volume fraction percolation threshold was determined. A progressive transformation of the water-in-oil to bicontinuous and inversion to oil-in-water microemulsions occurs upon dilution with water, which was revealed by the determination of the diffusion coefficients of both oil and water inside the microemulsions. The diffusion coefficients of the surfactants at the interface of the microemulsions increase with increasing water volume fraction. The periodicity of the microemulsions increases linearly with increasing water volume fraction. In addition, the correlation length increases with water volume fraction to a certain value then decreases. Cryo-TEM images of the oil-in-water microemulsions revealed the presence of spheroidal droplets of up to 12 nm diameter.

Microemulsion system with improved loading of piroxicam: a study of microstructure

Formulation of a new oil-in-water (o/w) microemulsion composed of castor oil/Tween 80/ethanol/phosphate buffer for enhancing the loading capacity of an anti-inflammatory drug piroxicam has been accomplished. The pseudo-ternary phase diagram has been delineated at constant surfactant/cosurfactant ratio (1:2). The internal structure of so created four-component system was elucidated by means of an analysis of isotropic area magnitudes in the phase diagram. Conductivity (sigma), kinematic viscosity (keta), and surface tension (gamma) studies with the variation in Phiw (weight fraction of aqueous phase) show the occurrence of structural changes from water-in-oil (w/o) microemulsion to oil-in-water (o/w). Along with the solubility and partition studies of piroxicam in microemulsion components, the changes in the microstructure of the microemulsion after incorporation of drug have been evaluated using pH, sigma, gamma, keta, and density studies. Piroxicam, a poorly water-soluble drug displayed high solubility (1.0%) in an optimum microemulsion formulation using ethanol (55.0%), Tween 80 (26.5%), castor oil (7.5%), and phosphate buffer (11.0%). The results have shown that the microemulsion remained stable after the incorporation of piroxicam. Fluorescence spectra analysis taking pyrene as fluorescent probe was performed, and the results showed that pyrene was completely solubilized in the oil phases of the bicontinuous microemulsions. The fluorescence spectrum of the model drug piroxicam was used to probe the intramicellar region of nonionic microemulsion. The results showed that the piroxicam was localized in the interfacial film of microemulsion systems more deeply in the palisade layer with ethanol as the cosurfactant.

Biocompatible microemulsions and their prospective uses in drug delivery

Efficacy of lipophilic drugs is often hindered due to their poor aqueous solubility leading to low absorption after in vivo administration. A part of the administered dose is absorbed and reaches the pharmacological site of action and the remainder causes toxicity and undesirable side effects due to unwanted biodistribution. Enhancement in drug efficacy and lowering of drug toxicity could be achieved through encapsulation and delivery of the lipophilic drugs in aqueous based delivery systems. Microemulsions are macroscopically homogeneous pseudoternary and ternary colloidal assemblies having polar and nonpolar micro domains. Their dispersed phases in nanodimension have good shelf-life (due to thermodynamic stability), large surface area, low viscosity (in some compositions), and ultraslow surface tension. These properties qualify them to be prospective drug delivery systems provided they are composed of biocompatible excipients. Due to the existence of polar, nonpolar, and interfacial microdomains, encapsulation of different kinds of drugs is possible. The review entails reports on development and characterization of biocompatible microemulsion systems and their evaluation as probable vehicles for encapsulation, stabilization, and delivery of bioactive natural products and prescription drugs.

Analysis of Tween based microemulsion in the presence of TB drug rifampicin

The purpose of present study was to formulate microemulsion composed of oleic acid+phosphate buffer (PB)+Tween 80+ethanol and to investigate its potential as drug delivery system for an antitubercular drug rifampicin. The pseudo-ternary phase diagram has been delineated at constant surfactant/cosurfactant ratio (K(m) 0.55). Conductivity (sigma) and viscosity (keta) studies with variation in Phi (weight fraction of aqueous phase) and omega (molar concentration ratio) show the occurrence of structural changes from water-in-oil (w/o) microemulsion to oil-in-water (o/w). Along with the solubility and partition studies of rifampicin in microemulsion components, the changes in the microstructure of the microemulsion after incorporation of drug have been evaluated using pH, sigma and keta studies. The results have shown that the microemulsion remained stable after the incorporation of rifampicin (in terms of optical texture and phase separation). In addition, the particle size analysis indicates that the microemulsion changes into o/w emulsion at infinite dilution. Dissolution studies infer that a controlled release of rifampicin is expected from o/w emulsion droplet.

Incorporation of Antitubercular Drug Isoniazid in Pharmaceutically Accepted Microemulsion: Effect on Microstructure and Physical Parameters

PURPOSE

The purpose of present study is to formulate microemulsion composed of oleic acid, phosphate buffer, Tween 80, ethanol and to investigate its potential as drug delivery system for an antitubercular drug isoniazid.

MATERIALS AND METHODS

The pseudo-ternary phase diagram (Gibbs Triangle) was delineated at constant surfactant/co-surfactant ratio (Km 0.55). Changes in the microstructure were established using conductivity (sigma), viscosity (eta), surface tension (gamma) and density measurements. Dissolution studies and particle size analysis were carried out to understand the release of isoniazid from the microemulsion formulation. Further, partitioning studies and spectroscopic analysis (FT-IR and (1)H NMR) was performed to evaluate the location of drug in the colloidal formulation.

RESULTS

Physico-chemical analysis of microemulsion system showed the occurrence of structural changes from water-in-oil to oil-in-water microemulsion. It has been observed that the microemulsion remained stable after the incorporation of isoniazid (in terms of optical texture, pH and phase separation). The changes in the microstructure of the microemulsion after incorporation of drug was analyzed on the basis of partition studies of isoniazid in microemulsion components and various parameters viz pH, sigma, eta,gamma. In addition, the particle size analysis indicates that the microemulsion changes into o/w emulsion at infinite dilution. The spectroscopic studies revealed that most of the drug molecules are present in the continuum region of an o/w microemulsion. Dissolution studies infer that a controlled release of drug is expected from o/w emulsion droplet. In the present system the release of isoniazid from microemulsion was found to be non-Fickian.

CONCLUSION

The present Tween based microemulsion appears beneficial for the delivery of the isoniazid in terms of easy preparation, stability, low cost, sustained and controlled release of a highly water soluble drug.