Optimal Microemulsion Research Articles

Formulation and Stability of Microemulsion Preparations From Secang Wood Extract (Caesalpinia Sappan L) and Virgin Coconut Oil (VCO)

Research has been conducted to make microemulsion preparations from virgin coconut oil (VCO) and secang wood extract. The purpose of this study was to determine the characteristics of secang wood extract with ethanol solvent, determine the Hydrophilic Lipophilic Balance (HLB) value of a mixture of three surfactants that can form the most stable microemulsion preparations, and determine the most optimal variation in the concentration of secang wood extract in secang microemulsion formulations.This study began with the manufacture of secang wood ethanol extract from secang wood powder and 96% ethanol, then tested for flavonoid levels. Furthermore, VCO microemulsions in a mixture of water with secang extract are made with variations in HLB values, namely 12, 13, 14, and 15. Microemulsions with HLB variations were tested for stability through organoleptical observations and turbidity values by storage treatment at room temperature, heating, and centrifugation. Microemulsions were also tested for free fatty acid (FFA) levels. After that, the preparation of microemulsions with the most stable HLB is carried out with variations in the concentration of secang wood extract in the formulation. Microemulsions with extract variations were tested for stability through organoleptical observation and turbidity values after 24 hours, heating, and centrifugation. Microemulsions with optimal concentrations of secang wood extract were tested for antioxidant activity. The secang extract produced from the extraction was reddish-brown in color and had total flavonoids equivalent to 230.6 mg QE/g samples. The most stable microemulsion from this study is a microemulsion with an HLB value of 15 with a ratio of water:extract:VCO:surfactant which is 65:2,5:2,5:30. The microemulsion features transparent red, 1 phase, and smells like Tween 80 with turbidity value below 1% during storage, heating, and centrifugation with microemulsion FFA value of 0.53%. Based on variations in the concentration of secang wood extract, the higher the concentration of the extract, the more unstable the microemulsion produced. The 3% secang extract microemulsion is the most optimal microemulsion with antioxidant activity (IC50) of 1.4573±0.2694 mg/mL.

Development microemulsion formulation combination of citronella and red ginger essential oil

Acne vulgaris is a skin health problem. Citronella oil contains citronellal, geraniol, geranial, β-citronellol, and neral, which have antibacterial properties. Meanwhile, red ginger oil contains gingerol, which has anti-inflammatory properties. These two ingredients are suitable for treating acne vulgaris. The aim of this study are to develop microemulsion formulation combination of citronella and red ginger essential oil. In this experimental study, a microemulsion combination of citronella essential oil and red ginger essential oil was made using Tween 80 as a surfactant and Transcutol® as a co-surfactant, with variations of S-mix (surfactant:cosurfactant) of 3:3, 4:2, and 4.5:1.5 ratios. As an oil carrier, isopropyl myristate is used. The microemulsions are formulated using a titration method. The microemulsion was then tested for characteristics and stability. The results show that the most optimal microemulsion formula was obtained with an S-mix ratio of 4:2 with a globule size of 21.64 nm, a Polydispersion Index of 0.15, and a zeta potential of -3.82. Its pH and viscosity meet the required specifications and are stable.

Development and Evaluation of Self-Microemulsifying Drug Delivery System for Improving Oral Absorption of Poorly Water-Soluble Olaparib.

The purpose of this study is to develop and evaluate a self-microemulsifying drug delivery system (SMEDDS) to improve the oral absorption of poorly water-soluble olaparib. Through the solubility test of olaparib in various oils, surfactants and co-surfactants, pharmaceutical excipients were selected. Self-emulsifying regions were identified by mixing the selected materials at various ratios, and a pseudoternary phase diagram was constructed by synthesizing these results. The various physicochemical properties of microemulsion incorporating olaparib were confirmed by investigating the morphology, particle size, zeta potential, drug content and stability. In addition, the improved dissolution and absorption of olaparib were also confirmed through a dissolution test and a pharmacokinetic study. An optimal microemulsion was generated in the formulation of Capmul® MCM 10%, Labrasol® 80% and PEG 400 10%. The fabricated microemulsions were well-dispersed in aqueous solutions, and it was also confirmed that they were maintained well without any problems of physical or chemical stability. The dissolution profiles of olaparib were significantly improved compared to the value of powder. Associated with the high dissolutions of olaparib, the pharmacokinetic parameters were also greatly improved. Taken together with the results mentioned above, the microemulsion could be an effective tool as a formulation for olaparib and other similar drugs.

Acacetin-loaded microemulsion for transdermal delivery: preparation, optimization and evaluation

Context Acacetin is reported as a potential drug candidate for the treatment of atrial fibrillation. However, clinical applications are limited by poor water solubility, limited ethanol solubility, and extremely low oral bioavailability. Objective The present study prepared and evaluated acacetin-loaded microemulsion (ME) to achieve efficient pharmacokinetics together with no or minimal invasiveness for transdermal delivery. Materials and methods The formulation of ME was determined by the water titration method based on solubility results. The optimized formulation was achieved by the simplex lattice experiment design. The optimized ME formulations FA, FB and FC (FA with 10% and 50% DMSO as enhancers, respectively) were evaluated by ex vivo permeation with Franz diffusion cell and excised mice skin. In vivo pharmacokinetic studies were also performed at 8 mg/kg in rats within 6 h by transdermal administration. Results The optimal ME (FA) was comprised of 12.2% caprylic acid decanoate monoditriglyceride (MCF-NF), 39.8% Smix (RH40: Trans = 2:1 w/w) and 48% water, respectively. Acacetin-loaded FA with particle size 36.0 ± 3.6 nm and drug solubility 803.7 ± 32.1 mg/g was prepared. FB had significantly higher cumulative amounts and higher AUC0-∞ (196.6 ± 11.0 min × μg/mL, p < 0.05) than that FA alone (121.4 ± 33.1 min × μg/mL). Discussion and conclusions The formulation of ME combined with the penetration enhancer can effectively improve the solubility and percutaneous absorption efficiency of acacetin, providing a new option for the non-invasive delivery of acacetin.

OPTIMASI FORMULA HAIR TONIC MIKROEMULSI BIOTIN (VITAMIN B7) DENGAN METODE FACTORIAL DESIGN

Loss becomes a problem in the hair that causes baldness. Biotin is a vitamin that nourishes hair and prevents hair loss. Biotin which is formulated in microemulsion tends to be transparent, has low viscosity and high solubility. Formula optimization was carried out to determine the concentration of span 80, tween 80, and PEG 400 in biotin microemulsion hair tonic. The research was conducted on an experimental basis using a factorial design method with 3 factors, namely span 80, tween 80, and PEG 400. The optimum microemulsion formula was determined using Design Expert 13 software using the Factorial Design method. Testing the physical quality of the preparation is carried out at the optimum formula. Optimization of biotin microemulsion hair tonic showed results of span 80 (20%), tween 80 (9.466%) and PEG 400 (5%) with a predicted viscosity of 46.75 cPs and globule size of 2.98 µm. Prediction testing and test results compared to the One Sample T-test showed results that were not significantly different with a significance value of &gt;0.05. The optimum formula has a viscosity value of 47.67 cPs and a globule size of 2.4 µm. The results obtained concluded that the optimal composition composition of the biotin microemulsion formula from the combination of span 80, tween 80 and PEG 400 which produces hair tonic with good effects and physical quality is span 80 20%, tween 80 9.47% and PEG 400 5%.

Topical Delivery of Diacetyl Boldine in a Microemulsion Formulation for Chemoprotection against Melanoma.

This study aimed to develop a microemulsion formulation for topical delivery of Diacetyl Boldine (DAB) and to evaluate its cytotoxicity against melanoma cell line (B16BL6) in vitro. Using a pseudo-ternary phase diagram, the optimal microemulsion formulation region was identified, and its particle size, viscosity, pH, and in vitro release characteristics were determined. Permeation studies were performed on excised human skin using Franz diffusion cell assembly. The cytotoxicity of the formulations on B16BL6 melanoma cell lines was evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay. Two formulation compositions were selected based on the higher microemulsion area of the pseudo-ternary phase diagrams. The formulations showed a mean globule size of around 50 nm and a polydispersity index of <0.2. The ex vivo skin permeation study demonstrated that the microemulsion formulation exhibited significantly higher skin retention levels than the DAB solution in MCT oil (Control, DAB-MCT). Furthermore, the formulations showed substantially higher cytotoxicity toward B16BL6 cell lines than the control formulation (p < 0.001). The half-maximal inhibitory concentrations (IC50) of F1, F2, and DAB-MCT formulations against B16BL6 cells were calculated to be 1 µg/mL, 10 µg/mL, and 50 µg/mL, respectively. By comparison, the IC50 of F1 was 50-fold lower than that of the DAB-MCT formulation. The results of the present study suggest that microemulsion could be a promising formulation for the topical administration of DAB.

From medicinal and food homologous biomass to total glycosides in Rehmannia glutinosa leaves extracts: Microemulsion-based negative pressure cavitation-assisted extraction

Food-grade and sustainable peppermint oil microemulsion was prepared through gradual screening of components for extraction of total glycosides in Rehmannia glutinosa leaves. The optimal microemulsion was: 6:3:1:25.71 (Tween 80: ethanol: peppermint oil: 0.02 mol/L KCl, w-w:w:w). 1 mol/L KCl solution was used for back-extraction to achieve sustainability of microemulsion. Microemulsion could be used at least 4 cycles. To optimize sustainability of microemulsion, negative pressure cavitation-assisted extraction technology was used as an auxiliary method. Which also makes extraction more suitable for large-scale industrial production. Consequently, microemulsion-based negative pressure cavitation-assisted extraction technology was developed. The optimal conditions for technology were as follows: 5.5 of pH, 37 min of time, and 10 mL/g of liquid-solid ratio. The yield of total glycosides was 45.13 mg/g. This newly established technology, as a cleaner alternative approach, can therefore be used to extract total glycosides from Rehmannia glutinosa leaves.

Microemulsion-based lutein extraction from marigold petals: Process optimization and stabilization evaluation

In present study, a novel, efficient and environmental friendly microemulsion extraction method was established to extract lutein from marigold petals powder (MPP). The optimum microemulsion formulation was obtained by combining the screening of oils, co-surfactants and ternary phase diagram. Based on the saturation solubility of lutein, isoamyl acetate and n-propanol were selected as oil phase and co-surfactant, respectively. A 5 mL microemulsion consisting of Tween80/n-propanol/isoamyl acetate/water (36:36:18:10 wt%) was used for the extraction of lutein from 20 mg MPP, with the highest extraction efficiency of 95.17%. For lutein microemulsion, the average droplet size was 26.44 ± 0.17 nm, the polydispersity index was 0.37 ± 0.00 and Zeta potential was − 11.20 ± 0.26 mV. Compared with ethanol extract (EE), MPP microemulsion extract (LME) had higher stability under different temperature, pH, and storage time conditions. This study would provide a new alternative method for lutein extraction, and also could be expected to be applied for other poorly water-soluble ingredients.

Review on Microemulsions for Conformance Improvement Technology: Fundamentals, Design Considerations, and Perspectives

The area of conformance improvement technology (CIT) encompasses the application of a myriad range of conventional fluids, including polymers, gels, foams, polymer-enhanced gels and foams, bacteria, and emulsions. However, these routes show operational limitations in terms of chemical degradation, thermal degradation, formation damage, susceptibility to high salinity, and segregation within pore spaces. To mitigate these problems, it is necessary to employ conformance agents that can be effectively tuned for a wide variety of reservoir conditions. Microemulsions are a promising class of fluids that exhibit thermodynamic stability, robust structure, and tunable properties. The concept of this research is to inject the optimal (correct) dosage of surfactants, which form micelles with in situ hydrocarbons to form microemulsions. Microemulsions are characterized by direct and reverse micelles, which contribute to their intermolecular interactions responsible for fluid stability and propagation under dynamic shear conditions. Design and reservoir considerations must comprise of a number of factors, namely, salinity, pH, temperature, slug concentration, and fluid activation/placement. An optimal microemulsion can be identified by understanding the flow mechanisms while accounting for mobility control, rock permeability and heterogeneity, thief zone permeabilities, and the presence of anomalies. It has been established in this review that microemulsions help plug the high permeability pore throats via a combination of the “Jamin effect” and viscosity modification. By adoption of a proper workflow design, the reservoir may be tuned via the introduction of microemulsions to suit the needs of the industry. However, considerable research is still needed to validate the design aspects and application of microemulsions for conformance improvement.

Formulation and stability of silkworm pupae oil microemulsion

Because of the instability, perishable odor and peculiar smell, a microemulsion system was designed to safely and effectively supply α-linolenic acid from silkworm pupae oil. Microemulsion-loaded silkworm pupae oil was prepared from isoamyl acetate, castor oil polyoxyethylene ether 35 (EL-35), ethanol and water. The optimal microemulsion formulation was a 4% composite oil phase (silkworm pupae oil: isoamyl acetate, 1:2), 16% composite surfactant (EL-35: ethanol, 2:1) and 80% water, with uniformly dispersed spherical particles with diameters of 16.25 nm. The color of the microemulsion was transparent and had no peculiar smell. The investigation results of environmental stress show that the transmittance is 86%–99%, and there is no significant difference from the control group (p > 0.05). Compared with silkworm pupae oil, the total antioxidant capacity of the microemulsion was increased by 7.70 times. Microemulsion-loaded silkworm pupae oil exhibited good physical and antioxidation stability. This work provides a feasible new scheme for ensuring the nutritional and health functions of silkworm pupae oil and supplying α-linolenic acid safely and effectively.

CHARACTERISTICS AND STABILITY OF IBUPROFEN MICROEMULSION PER INJECTION USING A COMBINATION OF MEDIUM-CHAIN TRIGLYCERIDE OIL, EXTRA VIRGIN OLIVE OIL, AND VIRGIN COCONUT OIL AS THE OIL PHASE

Injectable ibuprofen has been formulated as nanoemulsion, prodrug microemulsion, and freeze-dried. However, its application is limited because of solubility, high dosing, and complex formulation. Microemulsion ibuprofen injection is an alternative dosage form that increases solubility and bioavailability. The study aimed to formulate an ibuprofen microemulsion injection that can fulfill the prerequisites for injection preparations with a simple method and simple reconstitution before use. All combinations of the oil and aqueous phases were formed using the self-emulsification technique. The optimum stability was estimated on particle size, polydispersity index (PDI), and zeta potential at 5°C, 25°C, and 40°C for 120 days. Based on the minimum amount of Tween 80, drug loading, and the highest transmittance value, the optimal microemulsion formula was obtained at a concentration of 2.8% (1:1 combination of olive oil and medium-chain triglyceride oil), 11.2% Tween 80, 2.8% propylene glycol, and 83.2% water for injection. The optimal formula has a droplet size of 16.7 ± 11.2 nm, a zeta potential of 0.8 mV, and a PDI of 0.196. The formula was stable at 45°C storage for up to 14 days, at 25°C, and at 5°C, steady at 120 days based on droplet size diameter of 21.27 ± 0.00 nm, zeta potential -1.3 ± 0.10 mV, and PDI 0.38 ± 0.02. The optimum formula by simple reconstitution without additional isotonization has fulfilled the requirements for injection preparation. It was concluded that the ibuprofen microemulsion with a combination of medium-chain triglyceride oil and olive oil could form a stable microemulsion and has the potential to be developed as a pharmaceutical preparation in the form of injectable ibuprofen.

Microemulsion interface model for chemical enhanced oil recovery design

The surfactant phase behavior laboratory test for chemical enhanced oil recovery (EOR) formulation design is time consuming. However, it is possible to use computational chemistry simulation to minimize the duration. The only known non-empirical approach to predict surfactant phase behavior is by surface tension analysis, but the optimum phase behavior boundary is unclear and its applicability in actual complex crude oil is unproven. This research overcomes these issues by developing a microemulsion interface model using digital oil model with accurate representation of atomistic components of actual crude oil as inputs to the simulation. The microemulsion interface model is developed based on physical chemistry of surface tension and torque concepts coupled with solution of interface bending rigidity in relation to surfactant solubilization and interface energy. The model is implemented in coarse-grained molecular dynamics simulation technique. The microemulsion interface model is verified with surfactant phase behavior laboratory data using actual crude oil. Good agreement for 12 out of 14 chemical EOR formulations between simulations and phase behavior laboratory results is achieved. This indicates that the main characteristics and physics of the formation of optimal microemulsion were captured correctly in the microemulsion interface model. The duration for surfactant phase behavior determination can be reduced from 14 days in laboratory down to 1.5 day by using the microemulsion interface model, resulting in 90%-time reduction. This faster and more informed formulation development process can minimize time and costly resources as chemical EOR formulations proceed into field implementation.

Development and optimization of finasteride-cinnamon oil-loaded ethanol-free microemulsions for transdermal delivery

Finasteride (FN) is an FDA-approved pharmacologic agent for androgenic alopecia in men. However, systemic adverse effects have been observed in the majority of patients, so topical formulations are preferred over oral administration. The objectives of this study were to develop and optimize ethanol-free microemulsion (ME) systems for the transdermal delivery of FN by using a Design Expert®. The components of MEs were screened. The hexagonal lattice design was used in this study. An FN-loaded ME composed of cinnamon oil (CNO) as the oil phase, Tween® 20 as the surfactant, propylene glycol as the cosurfactant and reverse osmosis water as the aqueous phase was prepared. The physicochemical characteristics of the ME, the FN content, and the in vitro skin permeation were then investigated. The response surface methodology and optimal FN-CNO-loaded MEs were estimated using Design Expert®. The optimal formulation was composed of 11.58% CNO, 58.42% surfactant mixture (Smix) and 30% water. The physicochemical characteristics of the optimal MEs were very close to the predicted values estimated by the computer software. Scanning electron microscopy images showed that the damage to hair fibers treated and not treated with optimal MEs was not significantly different. Our study successfully and optimally predicted ethanol-free ME systems for FN transdermal delivery.

Insights from a Box-Behnken Optimization Study of Microemulsions with Salicylic Acid for Acne Therapy.

The present study brings to attention a method to develop salicylic acid-based oil in water (O/W) microemulsions using a tensioactive system based on Tween 80, lecithin, and propylene glycol (PG), enriched with a vegetable oat oil phase and hyaluronic acid. The systems were physically characterized and the Quality by design approach was applied to optimize the attributes of microemulsions using Box–Behnken modeling, combined with response surface methodology. For this purpose, a 33 fractional factorial design was selected. The effect of independent variables namely X1: Tween 80/PG (%), X2: Lecithin (%), X3: Oil phase (%) was analyzed considering their impact upon the internal structure and evaluated parameters chosen as dependent factors: viscosity, mean droplet size, and work of adhesion. A high viscosity, a low droplet size, an adequate wettability—with a reduced mechanical work—and clarity were considered as desirable for the optimal systems. It was found that the optimal microemulsion which complied with the established conditions was based on: Tween 80/PG 40%, lecithin 0.3%, oat oil 2%, salicylic acid 0.5%, hyaluronic acid 1%, and water 56.2%. The response surface methodology was considered an appropriate tool to explain the impact of formulation factors on the physical properties of microemulsions, offering a complex pattern in the assessment of stability and quality attributes for the optimized formulation.

Microemulsion as solvent for naphthoquinones extraction from walnut (Juglans mandshurica Maxim) green husk using high voltage electrical discharge

• An efficient method for obtaining naphthoquinones from walnut husk was developed. • High voltage electric discharge extraction with microemulsion was explored. • The effects of microemulsion formula and discharge conditions were investigated. • High voltage electric discharge with microemulsion shows favorable superiority. Walnut green husks are a good source of natural naphthoquinones (NQs). In this study, a novel extraction strategy combining microemulsion and high voltage electric discharge (HVED) was proposed to extract the NQs from walnut green husks and maximize the value of this agro-byproduct. Firstly, the optimum microemulsion formula (ME8) for NQs extraction was determined among 17 microemulsions prepared with various contents ratios. Then the single factor experiments were conducted to explore the effect of discharge parameters (voltage, treatment time, liquid-solid ratio) on NQs yield. These parameters were further optimized by response surface methodology with Box-Behnken design, and the highest yield of NQs (67.1 ± 0.3 mg/g) was obtained under the predicted optimal conditions. The combination of HVED and microemulsion showed favorable synergistic preponderance and the NQs yield was 1.52 times higher than heating reflux extraction. Moreover, this strategy presented a competitive option to extract hydrophobic compounds in a less-organics-consumption way.

Research on evaluating, selecting and manufacturing the VPI SP chemical product for conducting field test to enhance oil recovery coefficient of oil fields in Cuu Long basin, offshore Vietnam

The Vietnam Petroleum Institute (VPI) is implementing a multi-task national level project entitled “Research, evaluate, select and develop a pilot programme for industrial application of solutions to improve oil recovery coefficient for clastic oil bearing reservoirs of oil fields in the Cuu Long basin, on the continental shelf of Vietnam”. Specifically, detailed evaluation studies have been carried out from geological characteristics, reservoir engineering, production to EOR mechanism to develop technical criteria for the process of manufacturing and evaluating the efficiency of the chemical system to optimise the laboratory scale, propose the production and injection scenarios to optimize the development plan as well as evaluate the efficiency of increasing oil recovery coefficient on the reservoir simulation model; conduct production at pilot scale and implement industrial application testing on the field scale for clastic oil bearing reservoir, Cuu Long basin.&#x0D; The article presents the results of research, evaluation, selection and successful manufacture of a VPI SP chemical system based on the combined mechanism of anionic - non-ionic surfactants and polymers to ensure satisfying the harsh technical requirements of oil fields in Vietnam such as resistance to high temperature, high pressure, high mineralisation, very low surface tension, optimal micro-emulsion, low adsorption onto reservoir rocks, reducing residual oil saturation in the reservoir. Results of the evaluation of increased efficiency of oil recovery on actual samples of Miocene reservoir showed an increase of over 21%. The VPI SP chemical system has been included in the plan of industrial-scale testing by Vietsovpetro in Bach Ho and other producing fields in the clastic sections of the Cuu Long basin.

Formulation and evaluation of a α-linolenic acid and vitamin E succinate microemulsion with low surfactant content and free of co-surfactant for use as a nutritional supplement

Herein, we have designed an alcohol-free and low-surfactant microemulsion to safely and effectively supply α-linolenic acid (ALA) and vitamin E (VE). Ternary phase diagrams show that the use of medium- or short-chain alcohols as the co-surfactant (CoS) was unfavorable for the formation of the ALA microemulsion due to the competitive hydrogen bonding effect and vitamin E succinate (VES) significantly increased the ALA microemulsion region by improving the hydrophilicity of the oil phase. The optimal microemulsion formulation (Mav) was 6.86% ALA, 1.14% VES, 12% surfactant and 80% water, with uniformly dispersed spherical particles with diameters of ~ 25.41 nm and viscosity of 35.17 mPa·s. The Mav was stable to high temperature, ionic strength and pH, and exhibited good physical and anti-oxidation stability. The Mav facilitated the release and hydrolysis of VES, indicating that the CoS-free microemulsion with low surfactant content is promising for the safe and effective supply of ALA and VE.

Antifungal Activity of Topical Microemulsion Containing Ziziphus spina-christi L. for the Treatment of Fungal Vaginitis

Background: vulvovaginal candidiasis (VVC) caused by Candida albicans and other Candida species are high-risk event in patients admitted to hospital. Ziziphus genus is a rich source of medicinal compounds, effective for the treatment or prevention of some diseases. Objectives: This study aimed to evaluate the antifungal effect of topical microemulsion containing Ziziphus spina-christi L (ZSC) extracts against Candida spp.Methods: Z. Spina-Christi was collected and extracted in a Soxhlet apparatus using the ethanol and methanol solvents. Microemulsions were formulated by varying the composition of surfactant (Tween 80) along with cosurfactant (propylene glycol), oil, and water and were characterized regarding their stability. The microemulsion without extract as placebo and the active microemulsion containing ZSC extract as active formulation were applied to test the antifungal activity against C. albicans, C. parapsilosis and C. krusei using well diffusion test. The optimal microemulsion was selected and then analyzed for average diameter of droplets, pH, viscosity and zeta potential.Results: The microemulsion containing ZSC ethanolic extract had a significant inhibitory effect on the different species of Candida, but the most inhibitory effect was found against C. albicans. Conclusion: The results of this study indicate that the ethanol extract has interesting antimicrobial properties and can used for the treatment of fungal infections. More research is required to check this plant performance to treat the Candidiasis.

Preparation, optimization and evaluation of transdermal therapeutic system of celecoxib to treat inflammation for treatment of rheumatoid arthritis.

The purpose of present study was to prepare transdermal therapeutic system that could enhance dissolution of poorly aqueous soluble drug Celecoxib and thus increase its skin permeation. Solubility studies screened triacetin as oil, cremophor RH 40 as surfactant and Polyethylene Glycol 400 as co-surfactant. Pseudoternary phase diagrams were constructed to find out microemulsion region. Independent variables (oil, Smix and water) concentration was used at high (+1) and low levels (-1) that would generate 17 different combinations of microemulsions. Microemulsions were characterized, optimized and evaluated. pH, viscosity, conductivities, refractive index, droplet size and poly-dispersity-index was investigated. Prepared microemulsions were oil in water, thermodynamically stable, isotropic, transparent, deflocculated and within narrow range of size. Mathematical equations and response surface plots related the independent and dependent variables. Optimum microemulsion ME6 was further incorporated with carbomer 940 gel base to produce microemulsion based gel. ME6 and its gel showed significant difference (p<0.05) from control gel. Stability studies showed prepared MEBG of celecoxib was stable during storage period. Skin irritation studies found the gel was safe and non-irritating to skin. Anti-inflammatory studies showed significant difference (p<0.05) compared to control gel. Thus, the therapeutic system was successfully developed and optimized using Box Behnken statistical design.

Preparation and characterization of an oil-in-water microemulsion of thiamethoxam and acetamiprid without organic solvent for unmanned aerial vehicle spraying

Spraying pesticides is an essential measure for crop protection in agricultural production process. However, the large organic solvents and surfactants usage of common pesticide formulations have caused concern about environmental pollution. In recent years, unmanned aerial vehicle (UAV) spraying has gained more and more attention because of its ability to reduce the usage of pesticide and replace traditional human-powered spraying equipment. Nevertheless, the potential pollution hazard, spray drift and loss of current pesticide formulations in actual aerial spraying also remain challenging to date. Based on the requirement of appropriative pesticide formulation for UAV spraying, a novel oil-in-water microemulsion of thiamethoxam and acetamiprid without any organic solvents was investigated in this study. Complex emulsifiers were proposed to increase the solubility of pesticides in water, which could avoid the addition of unnecessary organic solvents in microemulsions. The physicochemical properties and application performance of the microemulsions were determined using visual observation, Turbiscan technique, laser particle size, indoor spraying experiments, high-performance liquid chromatography with ultraviolet detection and transmission electron microscopy. The optimal microemulsion with the formulation of 10 % sodium dodecyl sulfate and 10 % fatty alcohol polyoxyethylene ether sulfate consisted of small particles with a mean diameter of 1.9 nm, and exhibited good stability, improved wettability, anti evaporation, and spraying performance with deposition coverage rate of 16.2 %. This study expanded the possibility of the preparation and development of environmentally friendly pesticide formulations applicable for UAV agricultural spraying.