Oil-in-water lecithin-based microemulsions as a potential delivery system for amphotericin B

The fabrication of multifunctional sodium alginate scaffold incorporating ibuprofen-loaded modified PLLA microspheres based on cryogenic 3D printing

A strategy to develop a multifunctional sodium alginate personalized scaffold with enhanced mechanical stability, osteogenesis activity and excellent anti-inflammatory activity by cryogenic 3 D printing combined with subsequent crosslinking with Sr²⁺ is proposed in this study. The ink for 3 D printing was prepared by dispersing modified PLLA droplets containing ibuprofen into sodium alginate aqueous solution using lecithin as stabilizer. The results showed that the drug-loaded microspheres formed from the low-temperature solidifying of the modified PLLA droplets were homogeneously dispersed in sodium alginate substrate, and the scaffold displayed a sustained drug release performance toward ibuprofen which endowed the scaffold with persistent anti-inflammatory effects. In vitro cell culture indicated that the lecithin not only acted as the stabilizer, but also stimulated the proliferation and mineralization of osteoblastic cells on the scaffold. Sr²⁺-crosslinking improved the mechanical properties and osteogenic activity of the scaffold.

Lecithins: A comprehensive review of their properties and their use in formulating microemulsions

Lecithins are a phospholipid-rich mixture recovered from the degumming process of crude vegetable oils. Since the nineteenth century, this by-product of oil processing has been used as a food and pharmaceutical ingredient. Lecithins' popularity as an ingredient in the pharmaceutical and food industries arises from their particular properties, such as their hydrophilic-lipophilic balance, critical micellar concentration, and assembly properties. However, there is limited knowledge of the use of lecithins to formulate pharmaceutical- and food-grade microemulsions. Unlike conventional emulsions, microemulsions are thermodynamically stable systems that offer long-term stability. Besides, microemulsions show nano-sized droplets, transparency, ease of preparation and scale-up, and do not require expensive equipment. This review aims to provide a comprehensive overview of lecithins, their properties, and their use in formulating microemulsions, a promising method to incorporate, protect, and deliver bioactive compounds in pharmaceutical and food products. PRACTICAL APPLICATIONS: Lecithins are a phospholipid-rich mixture recovered from the degumming process of crude vegetable oils. Since the nineteenth century, this by-product of oil processing has been used as a food ingredient. Lecithin phospholipids are commonly used as emulsifier agents in the food and pharmaceutical industries because of their particular properties. However, there is limited knowledge of the use of lecithins to formulate pharmaceutical- or food-grade microemulsions. Unlike conventional emulsions, microemulsions are stable systems that offer long-term stability, nano-sized droplets, transparency, ease of preparation and scale-up, and do not require expensive equipment. This review aims to provide a comprehensive overview of lecithins, their properties, and their use in formulating microemulsions, a promising method to incorporate, protect, and deliver bioactive compounds such as vitamins, flavors, antioxidants, nutrients, colors, antimicrobials, and polyphenols.

Herbal Drugs and Natural Products in the light of Nanotechnology and Nanomedicine for Developing Drug Formulations

Natural products and medicinal plants have played a vital role in providing healthcare and ensuring well-being for many civilizations since antiquity. It is estimated that around 50% of drugs in the market have a natural product origin especially medicinal plants and herbal drugs, animals, fungi, and marine organisms. Some of these biologically active constituents of extracts have low absorption and distribution which, as a result, lead to loss of bioavailability and efficacy and might hamper their applications in the clinic. To overcome these impediments for the formulation of herbal drugs, food supplements, and essential oils, several nanomedical approaches such as liposomes, microemulsions, polymeric nanoparticles, solid lipid nanoparticles (SLNs), liquid crystal systems (LC), and precursor systems for liquid crystals (PSLCs) have been proposed. Nanoparticles have been used to modify and ameliorate the pharmacokinetic and pharmacodynamic properties of different drugs, thus incorporating biotechnological systems may be useful to enhance the bioavailability and bioactivity of herbal drug formulations. Consequently, essential for any natural compounds is the extent of its absorption after being ingested and its ability to be distributed in various tissues or organs of the body. The present review article aims to give an overview of the recent advancements in developing herbal drug formulations based on nanoparticle technologies.

Development of a novel cannabinoid-loaded microemulsion towards an improved stability and transdermal delivery

The aim of this study was to develop a stable microemulsion (ME) for transdermal delivery of tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). The lipid-based vehicles were selected by screening cannabinoid solubility and the emulsifying ability of surfactants. Pseudo-ternary phase diagrams were constructed by formulation of cannabinoids with Capryol® 90 as oil phase, Tween® 80, Solutol® HS15, Procetyl® AWS, and Cremophor® RH40 as surfactants, ethanol as cosurfactant, and distilled water as the aqueous phase. A significant improvement in transmembrane flux (J_ss), permeability coefficient (K_p), and enhancement ratio (E_R) was found in one system compared to other formulations. This ME consisted of 1.0% (w/w) of cannabinoids, 5% (w/w) of Capryol® 90, 44% (w/w) S_mix (2:1, Procetyl® AWS and Ethanol) and 50.0% (w/w) of distilled water. Additionally, the effects of pH on the permeation of the cannabinoids were investigated. Based on the pH value THCA and CBDA-loaded ME exhibited the highest permeation at pH 5.17 and pH 5.25. After storing the pH-adjusted P2 ME and the optimized P2 ME for 180 days at 4℃ and 25℃, the content of cannabinoids was over 95%. Consequently, the cannabinoid-loaded ME system is a promising option for solubilizing and stabilizing lipophilic drugs like cannabinoids and utilize them for transdermal delivery.

Flow behavior of concentrated tricalcium phosphate suspensions in oil through injection for softgel encapsulation

Softgel encapsulation is an important manufacturing process used to produce convenient oral dosage forms of pharmaceuticals and dietary supplements. An important step in this process involves the injection of a fill material into a gelatin lined mold, and poor flow of the fill material during the injection may lead to undesired defects. We investigated the effect of fill composition on the injection behavior of an oil-based tricalcium phosphate (TCP) suspension containing lecithin by rheological measurements, capillary breakup extensional rheometry (CaBER), and high-speed flow visualization experiments. Shear rheology for TCP suspensions in soybean oil at concentrations of 27.8 wt% and 55.6 wt% showed shear thinning behaviors both with and without the addition of lecithin. Adding up to 0.5 wt% lecithin led to decreases in shear viscosity, while additions up to 1 wt% caused a slight increase. Results from CaBER and breakoff studies indicated that the length at which flow breakoff occurs was closely related to the Ohnesorge number, a dimensionless parameter representing the relative importance of viscous to surface-tension forces during breakoff, with higher values correlated to longer breakoff lengths. An optimal lecithin concentration exists for minimized TCP suspension viscosity which shortens flow breakoff times and improves softgel capsule seaming quality.

Microemulsion systems: from the design and architecture to the building of a new delivery system for multiple-route drug delivery

Poorly soluble active pharmaceutical ingredients (APIs) create major problems in drug dosage form formulation resulting in significant delays in drug pharmaceutical screening, impairing the drug dosage form production. Aiming to minimize the use of excipients for increasing drug apparent solubility and, as a result, its bioavailability, exploration of innovative approaches is an earnest need. Microemulsion is an alternative drug delivery system that emerged as a valuable tool to achieve safe formulations for insoluble compounds and to improve their biopharmaceutical properties and pharmacokinetics. This review aims to present the state of the art of microemulsion systems, bringing an overview about their origin and how they can be properly produced and thoroughly characterized by different approaches. Furthermore, comments on regulatory issues regarding stability assessment and toxicity evaluation are discussed. The review concludes with a current opinion on microemulsion systems. The overall objective of this work was to describe all the potentialities of microemulsion systems as a drug carrier for therapeutic purposes, highlighting the unique features of this nanotechnological platform. Display Image.

Preparation and Characterization of Microemulsions Based on Antarctic Krill Oil

Antarctic krill oil is high in nutritional value and has biological functions like anti-inflammation and hypolipidemic effects. But it has and unpleasant smell, and unsaturated fatty acids are prone to oxidative deterioration. Its high viscosity and low solubility in water make it difficult for processing. Microemulsion can be a new promising route for development of krill oil product. We determined a formula of krill oil-in-water microemulsion with krill oil: isopropyl myristate = 1:3 as oil phase, Tween 80:Span 80 = 8:2 as surfactant, ethanol as co-surfactant and the mass ratio of surfactant to co-surfactant of 3:1. After screening the formula, we researched several characteristics of the prepared oil-in-water microemulsion, including electrical conductivity, microstructure by transmission electron microscope and cryogenic transmission electron microscope, droplet size analysis, rheological properties, thermal behavior by differential scanning calorimeter and stability against pH, salinity, and storage time.

Interferon-gamma carrying nanoemulsion with immunomodulatory and anti-tumor activities

The therapeutic administration of cytokines has been introduced aiming to modulate the immune response system, seeking for different approaches to face pathologies such as cancer, auto immune and infectious diseases. The objective of this study was to investigate the effects of a stable oil-in-water (O/W) nanoemulsion system carrying the cytokine Interferon gamma (IFN-γ) on the activity of phagocytes and MCF-7 human breast cancer cells. Nanoemulsions were prepared through ultra-homogenization, and they consisted of distilled water, triglycerides of capric acid/caprylic, sorbitan-oleate, polysorbate 80, and 1-butanol. IFN-γ (100 ng ml^-1 ) was incorporated into two O/W nanoemulsion formulations, and these formulations were characterized in terms of their preliminary and accelerated physicochemical stability, rheological properties, droplet size, polydispersity and surface charge. We identified the most optimal IFN-γ nanoemulsion (IFN-γNE2), which remained stable under extreme temperature variations for 90 days, contained an average dose of 97 ng ml^-1 of IFN-γ and exhibited a biocompatible pH and a relative stable rheological profile. Cell viability and intracellular Ca²⁺ release assays conducted showed that IFN-γNE2 reduced the cell viability of MCF-7 cells without affecting the cell viability of phagocytes. Furthermore, IFN-γNE2 was able to induce cellular activity of phagocytes as evidenced by increased intracellular Ca²⁺ release in these cells. Our findings on this IFN-γ nanoemulsion suggest that it can be a promising therapeutic agent for immunostimulation and cancer treatment.

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

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

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.

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

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

An analytical GC-MS method to quantify methyl dihydrojasmonate in biocompatible oil-in-water microemulsions: physicochemical characterization and in vitro release studies

Microemulsions (MEs) loaded with methyl dihydrojasmonate (MJ) were developed to improve the aqueous solubility of this drug. The composition of the formulations ranged according to the oil/surfactant ratio (O/S). The MEs were characterized according to diameter of droplets, X-ray diffraction and polarized light microscopy. The MJ identification and quantification was performed by gas chromatography-mass spectrometry (GC-MS). The MJ showed a retention time of ∼16.7 min for all samples. The obtained correlation coefficient from the calibration graph was 0.991. The developed analytical method was effective enough to quantify low and high concentrations of MJ. The increase of the O/S ME ratio led to a reduction of the droplet diameter. All formulations showed an amorphous structure and the behavior varied between isotropic and anisotropic systems. A decrease in the release of MJ with the increase of the O/S ratio in the formulations was observed. The analytical method developed for the quantitative determination of MJ is suitable to detect and quantify the drug compound from different compositions of MEs in the in vitro release test, and by analogy in other prolonged effects related to the drug reservoir effect of these systems was observed, revealing that ME can be a promising nanocarrier for MJ delivery to tumor cells.

Structural Features and the Anti-Inflammatory Effect of Green Tea Extract-Loaded Liquid Crystalline Systems Intended for Skin Delivery

Camellia sinensis, which is obtained from green tea extract (GTE), has been widely used in therapy owing to the antioxidant, chemoprotective, and anti-inflammatory activities of its chemical components. However, GTE is an unstable compound, and may undergo reactions that lead to a reduction or loss of its effectiveness and even its degradation. Hence, an attractive approach to overcome this problem to protect the GTE is its incorporation into liquid crystalline systems (LCS) that are drug delivery nanostructured systems with different rheological properties, since LCS have both fluid liquid and crystalline solid properties. Therefore, the aim of this study was to develop and characterize GTE-loaded LCS composed of polyoxypropylene (5) polyoxyethylene (20) cetyl alcohol, avocado oil, and water (F25E, F29E, and F32E) with different rheological properties and to determine their anti-inflammatory efficacy. Polarized light microscopy revealed that the formulations F25, F29, and F32 showed hexagonal, cubic, and lamellar liquid crystalline mesophases, respectively. Rheological studies showed that F32 is a viscous Newtonian liquid, while F25 and F29 are dilatant and pseudoplastic non-Newtonian fluids, respectively. All GTE-loaded LCS behaved as pseudoplastic with thixotropy; furthermore, the presence of GTE increased the S values and decreased the n values, especially in F29, indicating that this LCS has the most organized structure. Mechanical and bioadhesive properties of GTE-unloaded and -loaded LCS corroborated the rheological data, showing that F29 had the highest mechanical and bioadhesive values. Finally, in vivo inflammation assay revealed that the less elastic and consistent LCS, F25E and F32E presented statistically the same anti-inflammatory activity compared to the positive control, decreasing significantly the paw edema after 4 h; whereas, the most structured and elastic LCS, F29E, strongly limited the potential effects of GTE. Thereby, the development of drug delivery systems with suitable rheological properties may enhance GTE bioavailability, enabling its administration via the skin for the treatment of inflammation.

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.

Preparation and Characterization of Microemulsions of Myricetin for Improving Its Antiproliferative and Antioxidative Activities and Oral Bioavailability

To improve the bioactivity and oral bioavailability of myricetin, a microemulsion formulation was successfully developed, which consisted of Cremophor RH40 (12%), Tween 80 (6%), Transcutol HP (9%), WL 1349 (18%), and distilled water (55%). With lower content of surfactants and higher stability after dilution and storage for 6 months, the optimized myricetin microemulsion (MYR-ME) could dramatically enhance the solubility of myricetin 1225 times that in water. MYR-ME significantly increased antiproliferative activity against human cancer cell HepG2 without influence on normal cell LO2. It also notably improved the cellular antioxidative activity of myricetin. Furthermore, the oral bioavailability of myricetin was remarkably enhanced by MYR-ME in Sprague-Dawley rats after oral administration, which was 14.43-fold that with myricetin suspension. Therefore, the MYR-ME developed here could be used as a potential carrier for myricetin with substantially enhanced bioactivities and bioavailability and might promote myricetin's future utilization in functional foods and cosmetics.

Phase Transitions of Isotropic to Anisotropic Biocompatible Lipid-Based Drug Delivery Systems Overcoming Insoluble Benznidazole Loading

Previous studies reported low benznidazole (BNZ) loading in conventional emulsions due to the weak interaction of the drug with the most common oils used to produce foods or pharmaceuticals. In this study, we focused on how the type of surfactant, surfactant-to-oil ratio w/w (SOR) and oil-to-water ratio w/w (OWR) change the phase behavior of different lipid-based drug delivery systems (LBDDS) produced by emulsion phase inversion. The surfactant mixture composed of soy phosphatidylcholine and sodium oleate (1:7, w/w, hydrophilic lipophilic balance = 16) stabilized medium chain triglyceride in water. Ten formulations with the clear aspect or less turbid dispersions (five with the SOR ranging from 0.5 to 2.5 and five with the OWR from 0.06 to 0.4) were selected from the phase behavior diagram to assess structural features and drug-loading capacity. The rise in the SOR induced the formation of distinct lipid-based drug delivery systems (nanoemulsions and liquid crystal lamellar type) that were identified using rheological measurements and cross-polarized light microscopy images. Clear dispersions of small and narrow droplet-sized liquid-like nanoemulsions, Newtonian flow-type, were produced at SOR from 0.5 to 1.5 and OWR from 0.12 to 0.4, while clear liquid or gel-like liquid crystals were produced at SOR from 1.5 to 2.5. The BNZ loading was improved according to the composition and type of LBDDS produced, suggesting possible drug location among surfactant layers. The cell viability assays proved the biocompatibility for all of the prepared nanoemulsions at SOR less than 1.5 and liquid crystals at SOR less than 2.5, demonstrating their promising features for the oral or parenteral colloidal delivery systems containing benznidazole for Chagas disease treatment.

Development and Characterization of a Biocompatible Soybean Oil-Based Microemulsion for the Delivery of Poorly Water-Soluble Drugs

The aim of this work was the development and characterization of a biocompatible microemulsion (ME) containing soybean oil (O), phosphatidylcholine/sodium oleate/Eumulgin®HRE40 as the surfactant mixture (S) and water or buffer solution as the aqueous phase (W), for oral delivery of the poorly water-soluble drugs sulfamerazine (SMR) and indomethacin (INM). A wide range of combinations to obtain clear oil-in-water (o/w) ME was observed from pseudo-ternary phase diagrams, which was greater after the incorporation of both drugs, suggesting that they acted as stabilizers. Drug partition studies indicated a lower affinity of the drugs for the oil domain when they were ionized and with increased temperature, explained by the fact that both drugs were introduced inside the oil domain, determined by nuclear magnetic resonance. High concentrations of SMR and INM were able to be incorporated (22.0 and 62.3 mg/mL, respectively). The ME obtained presented an average droplet size of 100 nm and a negative surface charge. A significant increase in the release of SMR was observed with the ME with the highest percentage of O, because of the solubilizing properties of the ME. Also, a small retention effect was observed for INM, which may be explained by the differences in the partitioning properties of the drugs.

Microemulsions based on a sunflower lecithin-Tween 20 blend have high capacity for dissolving peppermint oil and stabilizing coenzyme Q10

The objectives of the present study were to improve the capability of microemulsions to dissolve peppermint oil by blending sunflower lecithin with Tween 20 and to study the possibility of codelivering lipophilic bioactive compounds. The oil loading in microemulsions with 20% (w/w) Tween 20 increased from 3% (w/w) to 20% (w/w) upon gradual supplementation of 6% (w/w) lecithin. All microemulsions had particles of <12 nm that did not change over 70 d of storage at 21 °C. They had relatively low Newtonian viscosities and were physically and chemically stable after 50-200-fold dilution in water, resulting from similar hydrophile-lipophile-balance values of the surfactant mixture and peppermint oil. Furthermore, the microemulsions were capable of dissolving coenzyme Q10 and preventing its degradation at UV 302 nm, more significant for the microemulsion with lecithin. Therefore, natural surfactant lecithin can reduce the use of synthetic Tween 20 to dissolve peppermint oil and protect the degradation of dissolved lipophilic bioactive components in transparent products.

Development and characterization of biocompatible isotropic and anisotropic oil-in-water colloidal dispersions as a new delivery system for methyl dihydrojasmonate antitumor drug

Microemulsions (MEs) are colloidal systems that can be used for drug-delivery and drug-targeting purposes. These systems are able to incorporate drugs modifying bioavailability and stability and reducing toxic effects. The jasmonate compounds belong to a group of plant stress hormones, and the jasmonic acid and its methyl ester derivative have been described as having anticancer activity. However, these compounds are very poorly water-soluble, not allowing administration by an intravenous route without an efficient nanostructured carrier system. In this work, biocompatible MEs of appropriate diameter size for intravenous route administration, loaded and unloaded with methyl dihydrojasmonate (MJ), were developed and described in a pseudo-ternary phase diagram. The compositions of the MEs were carefully selected from their own regions in the pseudo-ternary phase diagram. The formulations were analyzed by light scattering, polarized light microscopy, and X-ray diffraction. Also, a study on rheological profile was performed. The results showed that the droplet size decreased with both MJ incorporation and oil phase/surfactant ratio. All compositions of the studied MEs showed rheological behavior of pseudoplastic fluid and amorphous structures. In the absence of MJ, most of the studied MEs had thixotropic characteristics, which became antithixotropic in the presence of the drug. Almost all MJ-unloaded MEs presented anisotropic characteristics, but some formulations became isotropic, especially in the presence of MJ. The results of this study support the conclusion that the studied system represents a promising vehicle for in vivo administration of the MJ antitumor drug.

Nanotechnology-based drug delivery systems and herbal medicines: a review

Herbal medicines have been widely used around the world since ancient times. The advancement of phytochemical and phytopharmacological sciences has enabled elucidation of the composition and biological activities of several medicinal plant products. The effectiveness of many species of medicinal plants depends on the supply of active compounds. Most of the biologically active constituents of extracts, such as flavonoids, tannins, and terpenoids, are highly soluble in water, but have low absorption, because they are unable to cross the lipid membranes of the cells, have excessively high molecular size, or are poorly absorbed, resulting in loss of bioavailability and efficacy. Some extracts are not used clinically because of these obstacles. It has been widely proposed to combine herbal medicine with nanotechnology, because nanostructured systems might be able to potentiate the action of plant extracts, reducing the required dose and side effects, and improving activity. Nanosystems can deliver the active constituent at a sufficient concentration during the entire treatment period, directing it to the desired site of action. Conventional treatments do not meet these requirements. The purpose of this study is to review nanotechnology-based drug delivery systems and herbal medicines.

Development of oil-in-water microemulsions for the oral delivery of amphotericin B

Amphotericin B (AmB) is a very efficient drug against serious diseases such as leishmaniasis and systemic fungal infections. However, its oral bioavailability is limited due to its poor solubility in water. Nevertheless, it is marketed as high-cost lipid parenteral formulations that may induce serious infusion-related side effects. In this study, oil-in-water (O/W) microemulsions (MEs) were developed and characterized with a view to their use as solubility enhancers and oral delivery systems for AmB. Therefore, different nonionic surfactants from the Tween(®) and Span(®) series were tested for their solubilization capacity in combination with several oils. Based on pseudoternary phase diagrams, AmB-loaded MEs with mean droplet sizes about 120 nm were successfully produced. They were able to improve the drug solubility up to 1000-fold. Rheological studies showed the MEs to be low-viscosity formulations with Newtonian behavior. Circular dichroism and absorption spectra revealed that part of the AmB in the MEs was aggregated as an AmB reservoir carrier. Cytotoxicity studies revealed limited toxicity to macrophage-like cells that may allow the formulations to be considered as suitable carriers for AmB.

Corneal absorption of a new riboflavin-nanostructured system for transepithelial collagen cross-linking

Corneal collagen cross-linking (CXL) has been described as a promising therapy for keratoconus. According to standard CXL protocol, epithelium should be debrided before treatment to allow penetration of riboflavin into the corneal stroma. However, removal of the epithelium can increase procedure risks. In this study we aim to evaluate stromal penetration of a biocompatible riboflavin-based nanoemulsion system (riboflavin-5-phosphate and riboflavin-base) in rabbit corneas with intact epithelium. Two riboflavin nanoemulsions were developed. Transmittance and absorption coefficient were measured on corneas with intact epithelia after 30, 60, 120, 180, and 240 minutes following exposure to either the nanoemulsions or standard 0.1% or 1% riboflavin-dextran solutions. For the nanoemulsions, the epithelium was removed after measurements to assure that the riboflavin had passed through the hydrophobic epithelium and retained within the stroma. Results were compared to de-epithelialized corneas exposed to 0.1% riboflavin solution and to the same riboflavin nanoemulsions for 30 minutes (standard protocol). Mean transmittance and absorption measured in epithelialized corneas receiving the standard 0.1% riboflavin solution did not reach the levels found on the debrided corneas using the standard technique. Neither increasing the time of exposure nor the concentration of the riboflavin solution from 0.1% to 1% improved riboflavin penetration through the epithelium. When using riboflavin-5-phosphate nanoemulsion for 240 minutes, we found no difference between the mean absorption coefficients to the standard cross-linking protocol (p = 0.54). Riboflavin nanoemulsion was able to penetrate the corneal epithelium, achieving, after 240 minutes, greater stromal concentration when compared to debrided corneas with the standard protocol (p = 0.002). The riboflavin-5-phosphate nanoemulsion diffused better into the stroma than the riboflavin-base nanoemulsion.

Effects of oil and drug concentrations on droplets size of palm oil esters (POEs) nanoemulsion

Aim of the present work is to study the effects of oil and drug concentrations on droplets size of a nanoemulsion. Newly introduced oil, palm oil esters (POEs) by Universiti Putra Malaysia researchers was selected for the oil phase of the nanoemulsion, because the oil was reported to be a good vehicle for pharmaceutical use. Nanoemulsions were prepared with different concentrations of oil and drug and their effects on droplets size were studied by laser scattering spectroscopy (Nanophox). The results of droplets size analysis shows the droplets size increase with increasing concentration of oil and drug concentrations. It can be concluded from this study, that oil and drug concentrations have an effect on the droplets size of POEs nanoemulsion system.

A novel hydrophilic poly(lactide-co-glycolide)/lecithin hybrid microspheres sintered scaffold for bone repair

Novel 3-D porous scaffolds made of sintered poly(lacide-co-glycolide) (PLGA)/lecithin hybrid microspheres (PLGA/Lec-SMS) were developed and investigated. The addition of lecithin in PLGA bulk successfully managed the desired hydrophilic modification without sacrificing bulk properties. The outcomes were verified with infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and contact angle analyses. Specifically, this model of scaffold gained significant improvement in mechanical (mainly compressive) strength upon an optimization of lecithin fractions aligning with sintering conditions. Given a perspective of bone tissue engineering use, human fetal osteoblasts were seeded into a series of these PLGA/Lec-SMS scaffolds upon which key parameters of cytocompatibility and osteoconductivity (including cell viability, alkaline phosphatase activity, calcium secretion, and osteogenic genes expression) were assessed. Osteoblasts seeded on PLGA scaffolds with 5 wt % lecithin demonstrated high cell viability and alkaline phosphatase activity. Moreover, elevated lecithin also enhanced the expression of type I collagen. Taken together, these results suggest PLGA/Lec-SMS are promising scaffolds for bone repair.

Lipid microspheres loaded with antigenic membrane proteins of the Leishmania amazonensis as a potential biotechnology application

Lipid microspheres (LM) are excellent drug delivery or vaccines adjuvant systems and are relatively stable. The aim of this work is to develop and characterize a system that is able to encapsulate and present antigenic membrane proteins from Leishmania amazonensis. Membrane proteins are important for vaccine's formulation because these proteins come in contact with the host cell first, triggering the cell mediated immune response. This is a useful tool to avoid or inactivate the parasite invasion. The LM are constituted by soybean oil (SO), dipalmitoylphosphatidilcholine (DPPC), cholesterol and solubilized protein extract (SPE). The particles formed presented an average diameter of 200 nm, low polydispersion and good stability for a period of 30 days, according to dynamic light scattering assays. Isopycnic density gradient centrifugation of LM-protein showed that proteins and lipids floated in the sucrose gradient (5-50%w/v) suggesting that the LM-protein preparation was homogeneous and that the proteins are interacting with the system. The results show that 85% of SPE proteins were encapsulated in the LM. Studies of cellular viability of murine peritoneal macrophages show that our system does not present cytotoxic effect for the macrophages and still stimulates their NO production (which makes its application as a vaccine adjuvant possible). LM-protein loaded with antigenic membrane proteins from L. amazonensis seems to be a promising vaccine system for immunization against leishmaniasis.