Characterization of microemulsion structures in the pseudoternary phase diagram of isopropyl palmitate/water/Brij 97:1-butanol

Topical Microemulsions: Skin Irritation Potential and Anti-Inflammatory Effects of Herbal Substances

Microemulsions (MEs) have gained prominence as effective drug delivery systems owing to their optical transparency, low viscosity, and thermodynamic stability. MEs, when stabilized with surfactants and/or co-surfactants, exhibit enhanced drug solubilization, prolonged shelf life, and simple preparation methods. This review examines the various types of MEs, explores different preparation techniques, and investigates characterization approaches. Plant extracts and bioactive compounds are well established for their utilization as active ingredients in the pharmaceutical and cosmetic industries. Being derived from natural sources, they serve as preferable alternatives to synthetic chemicals. Furthermore, they have demonstrated a wide range of therapeutic effects, including anti-inflammatory, antimicrobial, and antioxidant activities. However, the topical application of plant extracts and bioactive compounds has certain limitations, such as low skin absorption and stability. To overcome these challenges, the utilization of MEs enables enhanced skin absorption, thereby making them a valuable mode of administration. However, considering the significant surfactant content in MEs, this review evaluates the potential skin irritation caused by MEs containing herbal substances. Additionally, the review explores the topical application of MEs specifically for herbal substances, with an emphasis on their anti-inflammatory properties.

A Novel Nanoemulsion Formula for an Improved Delivery of a Thalidomide Analogue to Triple-Negative Breast Cancer; Synthesis, Formulation, Characterization and Molecular Studies

Background

Thalidomide (THD) and its analogues were recently reported as a promising treatment for different types of solid tumors due to their antiangiogenic effect.

Methods

In this work, we synthesized a novel THD analogue (TA), and its chemistry was confirmed with different techniques such as IR, mass spectroscopy, elemental analysis as well as ¹H and ¹³C NMR. To increase solubility and anticancer efficacy, a new oil in water (O/W) nanoemulsion (NE) was used in the formulation of the analogue. The novel formula's surface charge, size, stability, FTIR, FE-TEM, in vitro drug release and physical characteristics were investigated. Furthermore, molecular docking studies were conducted to predict the possible binding modes and molecular interactions behind the inhibitory activities of the THD and TA.

Results

TA showed a significant cytotoxic activity with IC₅₀ ranging from 0.326 to 43.26 µmol/mL when evaluated against cancerous cells such as MCF-7, HepG2, Caco-2, LNCaP and RKO cell lines. The loaded analogue showed more potential cytotoxicity against MDA-MB-231 and MCF-7-ADR cell lines with IC₅₀ values of 0.0293 and 0.0208 nmol/mL, respectively. Moreover, flow cytometry of cell cycle analysis and apoptosis were performed showing a suppression in the expression levels of TGF-β, MCL-1, VEGF, TNF-α, STAT3 and IL-6 in the MDA-MB-231 cell line.

Conclusion

The novel NE formula dramatically reduced the anticancer dosage of TA from micromolar efficiency to nanomolar efficiency. This indicates that the synthesized analogue exhibited high potency in the NE formulation and proved its efficacy against triple-negative breast cancer cell line.

Dihydroartemesinin and Curcumin Based Self-Microemulsifying Drug Delivery System for Antimalarial Activity

Malaria is a significant global problem which still persists despite the development of various effective antimalarial drugs. It is challenging to treat this disease due to the parasite's complex life cycle and high recrudensce of antimalarial drugs. A new self-micro emulsifying drug delivery system has been developed to improve the solubility of dihydroartemisinin and curcumin. The prepared formulation contained Dihydroartemesinin, curcumin, Groundnut Oil, Cremephor RH, and Tween 80. Self-micro emulsification time, zeta potential, droplet size, polydispersity index, transmission electron microscopy, drug release, and in-vivo studies were performed for characterization. The globule size was found to be 25.59±0.40 nm and the zeta potential was-5.75±0.18 mV. The globules prepared were spherical in shape. The in-vitro dissolution performance of formulation of dihydroartemisinin and curcumin self emulsifying drug delivery system showed significantly (p<0.05, Origin Pro 8.5) higher release as compared to the pure drugs. The results of the study suggested that the prepared self emulsifying drug delivery system combination of Dihydroartemesinin and curcumin has a better potential to cure parasitemia as compared to the individual drug.

Mitigated Oxidative Stress and Cognitive Impairments in Transient Global Ischemia using Niosomal Selegiline-NBP delivery

Stroke is the most common reason for adult disabilities and the second ground for death worldwide. Our previous study revealed that selegiline serves as an alternative candidate in transient hypoxia-ischemia. However, aggressive and restless behavior was observed in stroke-induced rats receiving 4 mg/kg selegiline. In comparison, 1 mg/kg selegiline could induce negligible therapeutic effects on mitochondrial dysfunction and histopathological changes. Therefore, we designed oral noisome-based selegiline attached to 4-(4-nitrobenzyl) pyridine to improve transient global ischemia by attenuating cognitive impairments, oxidative stress, and histopathological injury. The investigation was performed in transient hypoxia-ischemia-induced rats by oral administration of nanoformulation containing selegiline (0.25-1 mg/kg) for 4 weeks (3 times a week). Novel object recognition (NOR) was considered to evaluate their cognitive dysfunction. Oxidative stress parameters and brain histopathological assessments were determined following the scarification of rats. Outstandingly, our data demonstrated slower selegiline release from niosomes relative to free drug, which was also in a controlled manner. Our data confirmed significant improvement in cognitive behavior in the NOR test, an increase in glutathione level and total antioxidant power, a decline in MDA and protein carbonyl level, as well as a decreased number of dead cells in histopathological assessment after being exposed to (0.5-1 mg/kg) selegiline-NBP nanoformulation. These data manifested that the selegiline-NBP nanoformulation (0.5-1 mg/kg) could significantly reduce oxidative damage, cognitive dysfunction, and histopathological damage compared to transient hypoxia-ischemia rats, which is 20 times lower than the therapeutic dose in humans. Therefore, the proposed nanoformulation would be capable as an alternative candidate without side effects in stroke.

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.

Nanoemulsions as novel nanocarrieres for drug delivery across the skin: In-vitro, in-vivo evaluation of miconazole nanoemulsions for treatment of Candidiasis albicans

In the current research, attempt is made to fabricate a nanoemulsion (NE) containing an antifungal agent. The prepared formulation has been expected to enhance skin penetration. It is also studied for in vitro drug release and toxicity assessment. Spontaneous titration method was used for preparation of NE. Prepared NE were characterized for their charge, size, morphology, rheological behaviour, drug release profile, skin permeability. The drug permeation and skin irritation were investigated. The in vitro antifungal activity was inspected using the well agar diffusion method. Miconazole NE showed good penetration in the skin as compared to marketed products. SEM showed semispherical shapes of the droplets. Zeta potential and zeta sizer showed that size was in nano ranges having positive charge.

Thermodynamic Investigation of Droplet-Droplet and Bubble-Droplet Equilibrium in an Immiscible Medium

In the absence of external fields, interfacial tensions between different phases dictate the equilibrium morphology of a multiphase system. Depending on the relative magnitudes of these interfacial tensions, a composite system made up of immiscible fluids in contact with one another can exhibit contrasting behavior: the formation of lenses in one case and complete encapsulation in another. Relatively simple concepts such as the spreading coefficient (SC) have been extensively used by many researchers to make predictions. However, these qualitative methods are limited to determining the nature of the equilibrium states and do not provide enough information to calculate the exact equilibrium geometries. Moreover, due to the assumptions made, their validity is questionable at smaller scales where pressure forces due to curvature of the interfaces become significant or in systems where a compressible gas phase is present. Here we investigate equilibrium configurations of two fluid drops suspended in another fluid, which can be seen as a simple building block of more complicated systems. We use Gibbsian composite-system thermodynamics to derive equilibrium conditions and the equation acting as the free energy (thermodynamic potential) for this system. These equations are then numerically solved for an example system consisting of a dodecane drop and an air bubble surrounded by water, and the relative stability of distinct equilibrium shapes is investigated based on free-energy comparisons. Quantitative effects of system parameters such as interfacial tensions, volumes, and the scale of the system on geometry and stability are further explored. Multiphase systems similar to the ones analyzed here have broad applications in microfluidics, atmospheric physics, soft photonics, froth flotation, oil recovery, and some biological phenomena.

Lipid-Based Nanocarriers for Ophthalmic Administration: Towards Experimental Design Implementation

Nanotherapeutics based on biocompatible lipid matrices allow for enhanced solubility of poorly soluble compounds in the treatment of ophthalmic diseases, overcoming the anatomical and physiological barriers present in the eye, which, despite the ease of access, remains strongly protected. Micro-/nanoemulsions, solid lipid nanoparticles (SLN) or nanostructured lipid carriers (NLC) combine liquid and/or solid lipids with surfactants, improving drug stability and ocular bioavailability. Current research and development approaches based on try-and-error methodologies are unable to easily fine-tune nanoparticle populations in order to overcome the numerous constraints of ocular administration routes, which is believed to hamper easy approval from regulatory agencies for these systems. The predictable quality and specifications of the product can be achieved through quality-by-design (QbD) implementation in both research and industrial environments, in contrast to the current quality-by-testing (QbT) framework. Mathematical modelling of the expected final nanoparticle characteristics by variation of operator-controllable variables of the process can be achieved through adequate statistical design-of-experiments (DoE) application. This multivariate approach allows for optimisation of drug delivery platforms, reducing research costs and time, while maximising the understanding of the production process. This review aims to highlight the latest efforts in implementing the design of experiments to produce optimised lipid-based nanocarriers intended for ophthalmic administration. A useful background and an overview of the different possible approaches are presented, serving as a starting point to introduce the design of experiments in current nanoparticle research.

Nanoemulsions Loaded with Amphotericin B: Development, Characterization and Leishmanicidal Activity

Leishmaniasis is one of the most neglected diseases in the world. Its most severe clinical form, called visceral, if left untreated, can be fatal. Conventional therapy is based on the use of pentavalent antimonials and includes amphotericin B (AmB) as a second-choice drug. The micellar formulation of AmB, although effective, is associated with acute and chronic toxicity. Commercially-available lipid formulations emerged to overcome such drawbacks, but their high cost limits their widespread use. Drug delivery systems such as nanoemulsions (NE) have proven ability to solubilize hydrophobic compounds, improve absorption and bioavailability, increase efficacy and reduce toxicity of encapsulated drugs. NE become even more attractive because they are inexpensive and easy to prepare. The aim of this work was to incorporate AmB in NE prepared by sonicating a mixture of surfactants, Kolliphor® HS15 (KHS15) and Brij® 52, and an oil, isopropyl myristate. NE exhibited neutral pH, conductivity values consistent with oil in water systems, spherical structures with negative Zeta potential value, monomodal size distribution and average diameter of drug-containing droplets ranging from 33 to 132 nm. AmB did not modify the thermal behavior of the system, likely due to its dispersion in the internal phase. Statistically similar antileishmanial activity of AmB-loaded NE to that of AmB micellar formulation suggests further exploring them in terms of toxicity and effectiveness against amastigotes, with the aim of offering an alternative to treat visceral leishmaniasis.

In vivo and in vitro biocompatibility study of novel microemulsion hybridized with bovine serum albumin as nanocarrier for drug delivery

The present study aimed to synthesize triacetin-microemulsion (T-ME) and T-ME hybridized with bovine serum albumin nanoparticles (T-BSA-ME) having narrow particle size distribution and versatile carrier systems as a novel microemulsion system. The suggested ME system was characterized by Fourier Transform Infrared spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Atomic Force Microscopy (AFM). The physicochemical properties of microemulsion system including particle size, PDI and ζ-potential, refractive index, Conductivity, %Transmittance, pH, and rheological behavior were also evaluated. In vivo biocompatibility was done using Median Lethal Dose (LD 50) calculated and trialed to evaluate the acute toxicity. In Addition, hemolysis and leukocyte proliferation assay were characterized to evaluate in-vitro biocompatibility of the suggested MEs systems. Moreover, cytotoxicity of MEs systems was also investigated on HFF-2 and HEK-293 cells. The presence of BSA NPs as a macromolecular biomaterial hybridized with T-ME reduced the cytotoxicity. The properties of the suggested MEs system proposed the T-ME hybridized with BSA-NPs as a promising candidate for co-delivery and multifunctional biomedicine applications.

Synthesis and Characterization of Covalently Crosslinked pH-Responsive Hyaluronic Acid Nanogels: Effect of Synthesis Parameters

Stable hyaluronic acid nanogels were obtained following the water-in-oil microemulsion method by covalent crosslinking with three biocompatible crosslinking agents: Divinyl sulfone, 1,4-butanediol diglycidyl ether (BDDE), and poly(ethylene glycol) bis(amine). All nanoparticles showed a pH-sensitive swelling behavior, according to the pKa value of hyaluronic acid, as a consequence of the ionization of the carboxylic moieties, as it was corroborated by zeta potential measurements. QELS studies were carried out to study the influence of the chemical structure of the crosslinking agents on the particle size of the obtained nanogels. In addition, the effect of the molecular weight of the biopolymer and the degree of crosslinking on the nanogels dimensions was also evaluated for BDDE crosslinked nanoparticles, which showed the highest pH-responsive response.

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.

Structural Characterization of Biocompatible Reverse Micelles Using Small-Angle X-ray Scattering, 31P Nuclear Magnetic Resonance, and Fluorescence Spectroscopy

The most critical problem regarding the use of reverse micelles (RMs) in several fields is the toxicity of their partial components. In this sense, many efforts have been made to characterize nontoxic RM formulations on the basis of biological amphiphiles and/or different oils. In this contribution, the microstructure of biocompatible mixed RMs formulated by sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) and tri- n-octylphosphine oxide (TOPO) surfactants dispersed in the friendly solvent methyl laurate was studied by using SAXS and ³¹P NMR and by following the solvatochromic behavior of the molecular probe 4-aminophthalimide (4-AP). The results indicated the presence of RM aggregates upon TOPO incorporation with a droplet size reduction and an increase in the interfacial fluidity in comparison with pure AOT RMs. When confined inside the mixed systems, 4-AP showed a red-edge excitation shift and confirmed the increment of interfacial fluidity upon TOPO addition. Also, the partition between the external nonpolar solvent and the RM interface and an increase in both the local micropolarity and the capability to form a hydrogen bond interaction between 4-AP and a mixed interface were observed. The findings have been explained in terms of the nonionic surfactant structure and its complexing nature expressed at the interfacial level. Notably, we show how two different approaches, i.e., SAXS and the solvatochromism of the probe 4-AP, can be used in a complementary way to enhance our understanding of the interfacial fluidity of RMs, a parameter that is difficult to measure directly.

Micropolarity and Hydrogen-Bond Donor Ability of Environmentally Friendly Anionic Reverse Micelles Explored by UV/Vis Absorption of a Molecular Probe and FTIR Spectroscopy

In the present work we show how two biocompatible solvents, methyl laurate (ML) and isopropyl myristate (IPM), can be used as a less toxic alternative to replace the nonpolar component in a sodium 1,4-bis-2-ethylhexylsulfosuccinate (AOT) reverse micelles (RMs) formulation. In this sense, the micropolarity and the hydrogen-bond ability of the interface were monitored through the use of the solvatochromism of a molecular probe (1-methyl-8-oxyquinolinium betaine, QB) and Fourier transform infrared spectroscopy (FTIR). Our results demonstrate that the micropolarity sensed by QB in ML RMs is lower than in IPM RMs. Additionally, the water molecules form stronger H-bond interactions with the polar head of AOT in ML than in IPM. By FTIR was revealed that more water molecules interact with the interface in ML/AOT RMs. On the other hand, for AOT RMs generated in IPM, the weaker water-surfactant interaction allows the water molecules to establish hydrogen bonds with each other trending to bulk water more easily than in ML RMs, a consequence of the dissimilar penetration of nonpolar solvents into the interfacial region. The penetration process is strongly controlled by the polarity and viscosity of the external solvents. All of these results allow us to characterize these biocompatible systems, providing information about interfacial properties and how they can be altered by changing the external solvent. The ability of the nontoxic solvent to penetrate or not into the AOT interface produces a new interface with attractive properties.

Development and Evaluation of a Novel Microemulsion of Dexamethasone and Tobramycin for Topical Ocular Administration

PURPOSE

The purpose of this study was to develop and evaluate a novel dexamethasone- and tobramycin-loaded microemulsion for its potential for treating anterior segment eye infections.

METHODS

The microemulsion was evaluated for pH, particle size, zeta potential, light transmittance, morphology, and in vitro drug release. Sterility of the microemulsion was evaluated by direct as well as plate inoculation methods. Anti-inflammatory activity of dexamethasone, bactericidal activity of tobramycin, and cytotoxicity of the microemulsion were assessed and compared to that of the marketed eye drop suspension (Tobradex^®). Histological evaluation was performed in bovine corneas to assess the safety of microemulsion in comparison to Tobradex suspension. In addition, the stability of the microemulsion was studied at 4°C, 25°C, and 40°C.

RESULTS

The pH of the microemulsion was close to the pH of tear fluid. The microemulsion displayed an average globule size under 20 nm, with light transmittance around 95%-100%. The aseptically prepared microemulsion remained sterile for up to 14 days. The cytotoxicity of the microemulsion in bovine corneal endothelial cells was comparable to that of the Tobradex suspension. The anti-inflammatory activity of dexamethasone and the antibacterial activity of tobramycin from the microemulsion were significantly higher than those of the Tobradex suspension (P < 0.05). Histological evaluation showed an intact corneal epithelium without any signs of toxicity, and the developed microemulsion was found to be stable at 4°C and 25°C for 3 months.

CONCLUSION

In conclusion, the developed microemulsion could be explored as a suitable alternative to the marketed suspension for treating anterior segment eye infections.

Fatty Acid Based Microemulsions to Combat Ophthalmia Neonatorum Caused by Neisseria gonorrhoeae and Staphylococcus aureus

The bacterial species Neisseria gonorrhoeae (N. gonorrhoeae) and Staphylococcus aureus (S. aureus) are amongst the main microorganisms that cause ophthalmia neonatorum. The current treatment involves the use of various antibiotics such as ciprofloxacin, cephalosporin, ceftriaxone and cefotaxime. However, this treatment strategy is becoming more ineffective due to the antibiotic resistance in N. gonorrhoeae. The current study explores the potential use of fatty acid based microemulsions (ME) to prevent N. gonorrhoeae and S. aureus infections in new-borns' eyes without harmful side effects such as corneal or conjunctiva irritation. Pseudo-ternary phase diagrams were constructed to evaluate microemulsion regions and six different α-linolenic acid based microemulsions were prepared. The prepared formulations were characterized for α-linolenic acid content, size, transparency, zeta potential, Polarized light Microscopy, antimicrobial activity and ex vivo ocular toxicity. The mean droplet size of the ME formulations was in the range of 190.4 to 350.5 nm and polydispersity index (PDI) values were in the range of 0.102 to 0.561. All formulations were found stable upon storage for at least 8 weeks. In addition, self-diffusion coefficients determined by nuclear magnetic resonance (NMR) reflected that the diffusability of water increased at higher than 30% w/w water, while that of fatty acids and surfactants was in reverse. The antimicrobial efficacy of microemulsions was determined against N. gonorrhoeae and S. aureus. It was concluded that all microemulsions have strong antimicrobial effects against N. gonorrhoeae and S. aureus. Finally, bovine corneal opacity permeability (BCOP) and hen's egg chorioallantoic (HET-CAM) tests results showed that all microemulsion formulations were not strong ocular irritants.

Anti-Inflammatory Activity of Babassu Oil and Development of a Microemulsion System for Topical Delivery

Babassu oil extraction is the main income source in nut breakers communities in northeast of Brazil. Among these communities, babassu oil is used for cooking but also medically to treat skin wounds and inflammation, and vulvovaginitis. This study aimed to evaluate the anti-inflammatory activity of babassu oil and develop a microemulsion system with babassu oil for topical delivery. Topical anti-inflammatory activity was evaluated in mice ear edema using PMA, arachidonic acid, ethyl phenylpropiolate, phenol, and capsaicin as phlogistic agents. A microemulsion system was successfully developed using a Span® 80/Kolliphor® EL ratio of 6 : 4 as the surfactant system (S), propylene glycol and water (3 : 1) as the aqueous phase (A), and babassu oil as the oil phase (O), and analyzed through conductivity, SAXS, DSC, TEM, and rheological assays. Babassu oil and lauric acid showed anti-inflammatory activity in mice ear edema, through inhibition of eicosanoid pathway and bioactive amines. The developed formulation (39% A, 12.2% O, and 48.8% S) was classified as a bicontinuous to o/w transition microemulsion that showed a Newtonian profile. The topical anti-inflammatory activity of microemulsified babassu oil was markedly increased. A new delivery system of babassu microemulsion droplet clusters was designed to enhance the therapeutic efficacy of vegetable oil.

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

HYPOTHESIS

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

EXPERIMENTS

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

FINDINGS

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

Formulation of Propolis Phenolic Acids Containing Microemulsions and Their Biopharmaceutical Characterization

Microemulsions (MEs) were formulated using PEG-8 caprylic/capric glycerides and ethanolic propolis extracts. Characterization of MEs was performed by determining mean droplet size, polydispersity index, stability under varying external factors, and formulation effect on delivery of phenolic compounds into the skin ex vivo. Essential oils were included into the formulations of MEs and their influence on physical characteristics of the nanostructured systems as well as penetration into epidermis and dermis were evaluated. The droplet size, their distribution, and stability of the formulated MEs were not affected. Presence of essential oils in the formulation increased penetration of phenolic compounds in general, but only the amount of ferulic acid increased significantly. Mean droplet size increased with increase of oily phase amount, suggesting that phenolic compounds and components of essential oils were not modifying the formation of the interphase film composition and/or structure. Phenolic compounds were predominantly located in the lipid phase of the MEs thus minimizing their availability at the surface of the skin.

Microemulsions based on paeonol-menthol eutectic mixture for enhanced transdermal delivery: formulation development and in vitro evaluation

In this work, microemulsion-based gels were prepared for transdermal delivery of paeonol. Microemulsions containing eutectic mixtures of paeonol and menthol were developed. The obtained microemulsions were evaluated for particle size, viscosity and physical stability. The selected microemulsions were incorporated into Carbopol gels. Drug crystallization behavior during a short-term storage was compared and in vitro permeation and deposition study were conducted on mouse skin. Results showed that the eutectic liquids of paeonol and menthol at all ratio (6:4, 5:5 and 4:6) could form microemulsions but with significantly different physical characteristics. As the ratio of paeonol increased, the prepared microemulsions exhibited larger droplet size, higher viscosity and quicker crystal growth. Microemulsion containing paeonol and menthol at a ratio of 4:6 possessed the smallest size of 27 nm. Accordingly, the related gel showed better physical stability during 10 days of storage, as well as the highest percent of drug deposition (111.8 μg/cm²) and steady-state flux (0.3 μg/cm² h). These results suggested that the microemulsion formulation is a preferable approach for enhanced skin permeation, and the microemulsion based on drug-menthol eutectic mixture might be used as a potential transdermal delivery system for better therapeutic efficacy.

Match of Solubility Parameters Between Oil and Surfactants as a Rational Approach for the Formulation of Microemulsion with a High Dispersed Volume of Copaiba Oil and Low Surfactant Content

PURPOSE

Aim was to formulate oil-in-water (O/W) microemulsion with a high volume ratio of complex natural oil, i.e. copaiba oil and low surfactant content. The strategy of formulation was based on (i) the selection of surfactants based on predictive calculations of chemical compatibility between their hydrophobic moiety and oil components and (ii) matching the HLB of the surfactants with the required HLB of the oil.

METHOD

Solubility parameters of the hydrophobic moiety of the surfactants and of the main components found in the oil were calculated and compared. In turn, required HLB of oils were calculated. Selection of surfactants was achieved matching their solubility parameters with those of oil components. Blends of surfactants were prepared with HLB matching the required HLB of the oils. Oil:water mixtures (15:85 and 25:75) were the titrated with surfactant blends until a microemulsion was formed.

RESULTS

Two surfactant blends were identified from the predictive calculation approach. Microemulsions containing up to 19.6% and 13.7% of selected surfactant blends were obtained.

CONCLUSION

O/W microemulsions with a high volume fraction of complex natural oil and a reasonable surfactant concentration were formulated. These microemulsions can be proposed as delivery systems for the oral administration of poorly soluble drugs.

Design and Formulation of Optimized Microemulsions for Dermal Delivery of Resveratrol

The objective of this study was to formulate optimal formulations of microemulsions (MEs) and evaluate their feasibility for delivery of resveratrol into human skin ex vivo. Oil-in-water MEs were formulated using surfactant (S) PEG-8 caprylic/capric glycerides and cosurfactant (CoS) polyglyceryl-6-isostearate. Ethyl oleate was used as an oily phase. MEs were formulated using 5 : 1, 6 : 1, and 7 : 1 surfactant and cosurfactant (S : CoS) weight ratios. Pseudoternary phase diagrams were constructed and optimal compositions of MEs were obtained using Design Expert software. Mean droplet size for optimized ME formulations was determined to be 68.54 ± 1.18 nm, 66.08 ± 0.16 nm, and 66.66 ± 0.56 nm for systems with S : CoS weight ratios 5 : 1, 6 : 1, and 7 : 1, respectively. Resveratrol loading resulted in mean droplet size increase. The distribution of droplet size between fractions changed during storage of formulated MEs. Results demonstrated the increase of number of droplets and relative surface area when S : CoS weight ratios were 6 : 1 and 7 : 1 and the decrease when S : CoS weight ratio was 5 : 1. The highest penetration of resveratrol into the skin ex vivo was determined from ME with S : CoS weight ratio 5 : 1. It was demonstrated that all MEs were similar in their ability to deliver resveratrol into the skin ex vivo.

Dimethyl silicone dry nanoemulsion inhalations: Formulation study and anti-acute lung injury effect

Acute lung injury (ALI) is a severe disease, leading to death if not treated quickly. An emergency medicine is necessary for ALI therapy. Dimethyl silicone (DMS) is an effective agent to defoam the bubbles in the lung induced by ALI. However, DMS aerosols, a marketed formulation of DMS, affect environments and will be limited in the future. Here we firstly report a dry nanoemulsion inhalation for pulmonary delivery. Novel DMS dry nanoemulsion inhalations (DSNIs) were developed in this study. The optimal formulation of stable and homogenous DMS nanoemulsions (DSNs) was composed of Cremophor RH40/PEG 400/DMS (4:4:2, w/w/w) and water. The DSNs showed the tiny size of 19.8 nm, the zeta potential of -9.66 mV, and the low polydispersity index (PDI) of 0.37. The type of DSNs was identified as oil-in-water. The DSNs were added with mannitol followed by freeze-drying to obtain the DSNIs that were loose white powders, showed good fluidity, and were capable of rapid reconstitution to DSNs. The DSNs could adhere on the surfaces of lyophilized mannitol crystals. The aerodynamic diameter of DSNIs was 4.82 μm, suitable for pulmonary inhalation. The in vitro defoaming rate of DSNIs was 1.25 ml/s, much faster than those of the blank DSNIs, DMS, and DMS aerosols. The DSNIs showed significantly higher anti-ALI effect on the ALI rat models than the blank DSNIs and the DMS aerosols according to lung appearances, histological sections, and lung wet weight/dry weight ratios. The DSNIs are effective anti-ALI nanomedicines. The novel DMS formulation is a promising replacement of DMS aerosols.

Self-Microemulsifying Drug Delivery Systems: An Attractive Strategy for Enhanced Therapeutic Profile

Ease of administration and painless approach made oral route the most preferred. Poor oral bioavailability is pronounced with the majority of recent active ingredients because of dissolution rate limited absorption. Failure to attain intended therapeutic effect of the poor water soluble drugs by this route led to development of novel drug delivery systems which will fulfill therapeutic needs with minimum dose. Although many formulation approaches like solid dispersions, complexation, pH modification, and cocrystals exist, lipid based delivery systems finding increased appliance with the apparent increase in absorption of drug. Among lipid based formulations, self-microemulsifying formulations (droplet size < 100 nm) are evident to improve the oral bioavailability of hydrophobic drugs primarily due to their efficiency in facilitating solubilization and in presenting the hydrophobic drug in solubilized form whereby dissolution process can be circumvented. Various components that are used to formulate these dosage forms like surfactants and lipids contribute to the overall improvement in oral bioavailability via promoting the lymphatic transport; thereby hepatic first pass metabolism can be surmounted. The present paper gives exhaustive information on the formulation design and characterization of SMEDDS along with the probable mechanisms by which the bioavailability can be improved with SMEDDS.

Evaluation of nicotinamide microemulsion on the skin penetration enhancement

This study purposed to evaluate a microemulsion containing nicotinamide for its characteristics, stability, and skin penetration and retention comparing with a solution of nicotinamide in 2:1 mixture of water and isopropyl alcohol (IPA). The microemulsion system was composed of 1:1 mixture of Span80 and Tween80 as a surfactant mixture, isopropyl palmitate (IPP) as an oil phase, and 2:1 mixture of water and IPA as an aqueous phase. Nicotinamide microemulsion was prepared by dissolving the active in the aqueous phase before simply mixing with the other components. It was determined for its characteristics and stability under various conditions. The skin penetration and retention studies of nicotinamide microemulsion and solution were performed by modified Franz diffusion cells, using newborn pig skin as the membrane. The results showed that nicotinamide microemulsion could be obtained as clear yellowish liquid, was water-in-oil (w/o) type, possessed Newtonian flow, and exhibited physicochemical stability when kept at 4 °C and room temperature (≈30 ± 2 °C) during 3 months. From the skin penetration data, the microemulsion could enhance the skin penetration of nicotinamide comparing with the solution. Additionally, nicotinamide microemulsion could provide much higher amount of skin retention than that of skin penetration, resulting in suitability for a cosmeceutical product.

Relationship between composition and organizational levels of nanostructured systems formed by Oleth 10 and PPG-5-Ceteth-20 for potential drug delivery

In this paper, nanostructured systems were developed, with the aid of ternary phase diagrams, from two surfactants, of differing degrees of lipophilicity (PPG-5-Ceteth-20 and the Oleth 10) and two oil phases (oleic acid and isopropyl myristate). It was observed that there were differences between the four resulting phase diagrams in the physical properties of the systems they represent. Thus, due to the capacity of Oleth 10 (as surfactant) and oleic acid (as the oil phase) to reduce interfacial tension, large regions of translucent systems were seen on the diagrams produced by them. By polarized light microscopy, it was possible to identify the isotropic and anisotropic properties of these systems, which were confirmed by small-angle X-ray scattering (SAXS) analysis. Furthermore, it was found that increasing the proportion of water in the formulations led to more highly organized structures, resulting in narrower and well defined SAXS peaks.

A green protocol for the Pd catalyzed ligand free homocoupling reaction of arylboronic acids under ambient conditions

A simple, competent, green pathway has been developed for the Pd catalyzed ligand free homocoupling reaction of arylboronic acids in water under ambient conditions.

Formula Design of Pesticide Microemulsion Formulation

Microemulsions are regarded as one of the most promising pesticide formulations. However, formulation of pesticide microemulsions is not simple. Obtaining efficient, scientific and inexpensive formulation designs is challenging. In this work, cyhalothrin was used as a pesticide sample, and a systematic study on microemulsion formula design was carried out based on its pseudo-ternary phase diagram and the orthogonal design method. An explanation of the use of our approach is included to assist the formulator, and the development of a 5.28% w/w cyhalothrin microemulsion is described.

Microemulsion-based oxyresveratrol for topical treatment of herpes simplex virus (HSV) infection: physicochemical properties and efficacy in cutaneous HSV-1 infection in mice

The physicochemical properties of the optimized microemulsion and the permeating ability of oxyresveratrol in microemulsion were evaluated, and the efficacy of oxyresveratrol microemulsion in cutaneous herpes simplex virus type 1 (HSV-1) infection in mice was examined. The optimized microemulsion was composed of 10% w/w of isopropyl myristate, 35% w/w of Tween 80, 35% w/w of isopropyl alcohol, and 20% w/w of water. The mean particle diameter was 9.67 ± 0.58 nm, and the solubility of oxyresveratrol in the microemulsion was 196.34 ± 0.80 mg/ml. After accelerated and long-term stability testing, the microemulsion base and oxyresveratrol-loaded microemulsion were stable. The cumulative amount of oxyresveratrol permeating through shed snake skin from microemulsion at 6 h was 93.04 times compared to that of oxyresveratrol from Vaseline, determined at 20% w/w concentration. In cutaneous HSV-1 infection in mice, oxyresveratrol microemulsion at 20%, 25%, and 30% w/w, topically applied five times daily for 7 days after infection, was significantly effective in delaying the development of skin lesions and protecting from death (p < 0.05) compared with the untreated control. Oxyresveratrol microemulsion at 25% and 30% w/w was significantly more effective than that of 30% w/w of oxyresveratrol in Vaseline (p < 0.05) and was as effective as 5% w/w of acyclovir cream, topically applied five times daily (p > 0.05). These results demonstrated that topical oxyresveratrol microemulsion at 20-30% w/w was suitable for cutaneous HSV-1 mouse infection.

Lecithin-based microemulsions for targeted delivery of ceramide AP into the stratum corneum: formulation, characterizations, and in vitro release and penetration studies

PURPOSE

To improve the solubility and penetration of Ceramide AP (CER [AP]) into the stratum corneum that potentially restores the barrier function of aged and affected skin.

METHODS

CER [AP] microemulsions (MEs) were formulated using lecithin, Miglyol® 812 (miglyol) and water-1,2 pentandiol (PeG) mixture as amphiphilic, oily and hydrophilic components, respectively. The nanostructure of the MEs was revealed using electrical conductivity, differential scanning calorimeter (DSC) and electron paramagnetic resonance (EPR) techniques. Photon correlation spectroscopy (PCS) was used to measure the sizes and shape of ME droplets. The release and penetration of the CER into the stratum corneum was investigated in vitro using a multi-layer membrane model.

RESULTS

The MEs exhibited excellent thermodynamic stability (>2 years) and loading capacity (0.5% CER [AP]). The pseudo-ternary phase diagrams of the MEs were obtained and PCS results showed that the droplets are spherical in shape and bigger in size. In vitro investigations showed that the MEs exhibited excellent rate and extent of release and penetration.

CONCLUSIONS

Stable lecithin-based CER [AP] MEs that significantly enhance the solubility and penetration of CER [AP] into the stratum corneum were developed. The MEs also have better properties than the previously reported polyglycerol fatty acid surfactant-based CER [AP] MEs.