Lipid nanoparticles containing coenzyme Q10 for topical applications: An overview of their characterization.

The coenzyme Q10 is a compound widely used in pharmaceutical and cosmetic formulations because it is a potent eliminator of free radicals, giving it antioxidant and anti-aging properties. It is naturally synthesized by the human body, but its production wanes with age, leading to the formation of wrinkles. The efficacy of topical application of the coenzyme to counteract this process is subject to several difficulties, due to its instability in the presence of light, low solubility in water and high lipophilicity. Because of these drawbacks, many studies have been conducted of release systems. Lipid nanoparticles stand out in this sense due to the advantages of skin compatibility, protection of the active ingredient against degradation in the external medium, capacity to increase penetration of that ingredient in the skin, and its controlled and prolonged release. In this context, this article presents a review of the main studies of the coenzyme Q10 encapsulated in lipid nanoparticles for topical use, focusing on the analytic methods used to characterize the systems regarding morphology, zeta potential, release profile, Q10 content, encapsulation efficiency, crystalline organization and structure of the lipid matrix, rheology, antioxidant activity, skin penetration and efficacy, among other aspects. We also describe the main results of the different studies and discuss the critical aspects - the simplest, most reproducible, best, and most relevant - that characterize lipid nanoparticles with encapsulated Q10 for topical use.

Synthesis of Hydrogel Nanocomposites Based on Partially Hydrolyzed Polyacrylamide, Polyethyleneimine, and Modified Clay.

Polymeric gels have been an important category for material scientists due its versatile structural features. Hence, hydrogels are being used to reduce excess production water in oil reservoirs. In this work, cross-linked partially hydrolyzed polyacrylamide (HPAM) composite hydrogels impregnated with bentonite clay (Bent) and bentonite clay modified (Orgbentent) with the surfactant hexadecyltrimethylammonium bromide were synthesized and characterized as a sealing agent in high water producing permeable zones in the petroleum industry. The concept of utilizing hydrophobically modified clay as an inorganic additive in the hydrogel matrix emanates from the fact that this additive exhibit greater interaction with the polymer chains. These interactions can promote the inherent properties of the hydrogel. Polyethyleneimine (PEI) was chosen as the cross-linking agent. HPAM/PEI conventional hydrogels and HPAM/PEI/Bent and HPAM/PEI/Orgbent at 100 mg·L-1 clay were synthesized. The developed hydrogels were characterized by a hybrid rheometer and Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA) instruments. Rheological results reveal that the (HPAM/PEI/Bent-3 and HPAM/PEI/Orgbent-3) composite hydrogels showed higher elastic modulus (G') and durability in the studied conditions (stable at 30 days) than conventional ones (HPAM/PEI), indicating the dispersion and reinforcing effect of clay. The functional groups of these hydrogels were confirmed by FTIR, and TGA demonstrated the structural reinforcement due to the presence of the clays, which had lower weight loss than the conventional hydrogel. The hydrogel morphologies were analyzed by SEM, and the results corroborated with those obtained by TGA, indicating better structural reinforcement when using organophilic clay.

Development of Oil-in-Water Microemulsions and Evaluation of Its Presence in the Treatment of Produced Water.

Enhanced oil recovery (EOR) by chemical methods, such as injection of surfactants and polymers, increases the efficiency of extracting petroleum. However, after permeating the reservoir, these products remain in the produced water and hamper its treatment, including the efficiency reduction of the flocculants normally used for this purpose. In this work, oil-in-water (O/W) microemulsions were prepared according to ternary phase diagrams, with two oil phases, solbrax and kerosene, extracted from oil fractions, and two ethoxylated nonylphenol surfactants with 8 and 9.5 ethylene oxide units (NP80 and NP95), respectively, along with brine. The objective was to evaluate the effects of these components' presence in the microemulsions on the treatment of produced water. The microemulsified systems were characterized regarding viscosity, size of the dispersed droplets and stability. The results showed that the microemulsions containing the most polar surfactant (NP95) caused greater stabilization of the O/W emulsion (produced water). However, there also was a synergistic effect when using a commercial flocculant along with the microemulsion based on NP80, diminishing the residual oil content in the produced water.

Gelation Kinetics of Hydrogels Based on Acrylamide⁻AMPS⁻NVP Terpolymer, Bentonite, and Polyethylenimine for Conformance Control of Oil Reservoirs.

Relatively smaller volumes of gelling systems had been used to address conformance problems located near the wellbore in oil reservoirs with harsh temperature and salinity conditions. These gelling systems were formulated with high concentrations of low-molecular-weight acrylamide-based polymers crosslinked with polyethylenimine (PEI). However, for in-depth conformance control, in which large gelant volumes and long gelation times were required, lower-base polymer loadings were necessary to ensure the economic feasibility of the treatment. In this study, a gelling system with high-molecular weight 2-acrylamido-2-methylpropane sulfonic acid (AMPS), N-vinyl-2-pyrrolidone (NVP), acrylamide terpolymer, and PEI, with the addition of bentonite as a filler, was formulated. The influence of the gelant formulation and reservoir conditions on the gelation kinetics and final gel strength of the system was investigated through bottle tests and rheological tests. The addition of clay in the formulation increased the gelation time, thermal stability, and syneresis resistance, and slightly improved the final gel strength. Furthermore, samples prepared with polymer and PEI concentrations below 1 wt %, natural bentonite, and PEI with molecular weight of 70,000 kg/kmol and pH of 11: (i) presented good injectivity and propagation parameters (pseudoplastic behavior and viscosity ~25 mPa·s); (ii) showed suitable gelation times for near wellbore (~5 h) or far wellbore (~21 h) treatments; and (iii) formed strong composite hydrogels (equilibrium complex modulus ~10⁻20 Pa and Sydansk code G to H) with low syneresis and good long-term stability (~3 to 6 months) under harsh conditions. Therefore, the use of high-molecular-weight base polymer and low-cost clay as active filler seems promising to improve the cost-effectiveness of gelling systems for in-depth conformance treatments under harsh conditions of temperature and salinity/hardness.

Polymeric Nanostructured Systems for Liquid Formulation of Praziquan-tel: Development and in vitro Assessment.

Praziquantel (PZQ) is widely used in the treatment of several parasitic infections in both humans and animals, and is the first choice in the treatment of Schistosomiasis in humans. However, PZQ is a hydrophobic drug, and its low aqueous solubility has been a significant barrier to the development of oral liquid formulations that may provide improved bioavailability, pharmacokinetic profile, and compliance. The aim of this study was thus (i) to develop an oil-in-water (O/W) nanoemulsion(NE)-based platform for the delivery of PZQ in liquid form; (ii) to study the transport of PZQ formulated in NEs across an in vitro model of the intestinal epithelium; and (iii) to determine the toxicity profile of the NEs and their individual components on the model epithelium. We also sought to compare the toxicity and transport profiles of the proposed formulations, with those of PZQ in a solid nanostructured particle system - PZQ encapsulated within poly(lactic acid-co-glycolic acid) (PLGA) nanoparticles (NPs). Two essential oils were selected as the oil phase in the NEs, namely clove and orange. The NEs were prepared with selected non-ionic surfactants and had high solubilization capacity towards PZQ, and average diameters well below 100nm. The NEs also showed long term physical stability at both simulated physiological and gastric conditions. NEs with clove oil (NEC-PZQ) were observed to have a lower cytotoxic profile when compared to the orange oil NEs (NEO-PZQ). The results also showed that the transport of PZQ formulated within such nanostructured systems was much greater and larger rates across confluent and polarized Caco-2 monolayers when compared to free PZQ. Interestingly, little difference in PZQ transport between the NEs and NPs was observed. These results point to NEs as potentially viable strategies for the liquid formulation of PZQ in particular, and more broadly to the formulation of other hydrophobic therapeutics that may be employed in the fight against important neglected diseases such as Schistosomiasis, which alone affects more than 240 million people worldwide.

Nanosystems in Photoprotection.

The ultraviolet (UV) radiation is responsible for stimulating acute responses in the human skin, those including positive responses like vitamin D synthesis along with negative ones such as erythema. The chronic effects of UV radiation include photoaging and cancer. Sunscreens are classified as organic and inorganic and the safety of the products containing them is related to the evaluation of the effects of these actives on the skin (irritation and sensitization) and also the possibility of cutaneous permeation that may cause the product to permeate into the bloodstream, possibly generating systemic toxicity. Nanotechnology plays an important role in overcoming the obstacles related to sunscreens. In this context, there are the nanosystems that have been widely used as vehicles to sunscreens. The use of nanosystems aims to reduce phototoxicity and cutaneous permeation of sunscreens and also to act in improving the photostability, the sun protection factor (SPF) and the protection spectrum of sunscreens. The most studied nanosystems in photoprotection are: liposomes, nanoparticles (lipid, polymeric and inorganic), cyclodextrins and nanoemulsions.

Development and Evaluation of Nanoemulsions Containing Phthalocyanines for Use in Photodynamic Cancer Therapy.

This work reports the development of oil in water (o/w) nanoemulsions containing poly(ethylene oxide)-poly(propylene oxide) block copolymer surfactant for the formulation of a delivery system for endovenous zinc and chloroaluminum phthalocyanines. A solubility study suggested clove oil and its combination with ethanol as the best candidates for the oil phase composition. The nanoemulsions were obtained using a high-pressure homogenizer and analyzed for droplet size to determine their short- and long-term stability. Formulations containing 7 and 10% oil phase and 12% surfactant presented higher stability and allowed the incorporation of a bigger amount of phthalocyanines in the formulation. Rheological analyses showed the prevailing Newtonian behavior of the nanoemulsions. Studies of toxicity and phototoxicity determined that the nanoemulsions produced were capable of inhibiting the growth of adenocarcinoma tumor cells. The nanoemulsions proved to be a good alternative for use in photodynamic therapy.

Determination of oil-in-water using nanoemulsions as solvents and UV visible and total organic carbon detection methods.

The aim of this study was to investigate the application of oil in water (O/W) nanoemulsion as solvent in the extraction step for determination of oil content in oily water, measured using a UV visible spectrophotometer (UV-vis) and a total organic carbon (TOC) analyzer. The optical micrographs and distribution size curves showed that the use of a small amount of nanoemulsion was capable of transforming the oily water in a colloidal dispersion that can be read in the UV-vis and TOC-VCHS devices. The oil content results obtained showed great accuracy between the measurements, with very low average standard deviation (∼5%) for both UV-vis and TOC-VCHS. The new methods suggested in this work are very promising, since they allow simple, quick and accurate analyses, and especially require a lower volume of solvent (less than 1%) compared to those used in conventional analytic methods.

Nanoemulsions containing octyl methoxycinnamate and solid particles of TiO2: preparation, characterization and in vitro evaluation of the solar protection factor.

The objective of this work was to develop and evaluate the physical-chemical properties of oil-in-water nanoemulsions for application as nanocosmetics for sun protection. Oil-in-water dispersions were processed by ultrasound (US) to obtain small emulsion droplets. These emulsions were obtained in the presence of commercial nonionic surfactants based on polyoxides and avocado oil as the oil phase. The US generated small but unstable droplets. This problem was solved by using a different surfactant, with a longer ethylene oxide chain, able to promote stabilization by steric mechanisms. The light scattering technique was used to characterize the nanoemulsions by their dispersed droplets' size, size distribution and variation of distribution with time (stability). Chemical and physical sunscreens - octyl methoxycinnamate (OMC) and titanium dioxide (TiO2), respectively - were added to the stable system. The anti-UVB activity of the nanoemulsions and their components were evaluated by the method of Mansur et al. (1986) and spectral transmittance. The solar protection factor (SPF) was proportional to the OMC and TiO2 concentrations. The in vitro OMC release was evaluated, and the presence of TiO2 in the nanoemulsion did not affect the release profile, which showed the diffusion-dependent kinetics of the active ingredient in the formulation.

The application of nanoemulsions with different orange oil concentrations to remediate crude oil-contaminated soil.

The petroleum industry stands out for causing significant environmental risks from contamination of the air, water and soil. The removal of organic pollutants from the environment poses a great technological challenge, making it increasingly necessary to develop efficient clean-up technologies. Surfactant solutions have been used to remediate soils and aquifers contaminated by hydrocarbons or crude oil derivatives. The aim of this study was to develop nanoemulsions and analyze their efficiency in extracting crude oil from a sand sample. The nanoemulsions were prepared by the phase inversion temperature (PIT) method. The oil phase consisted of orange oil and the nonionic surfactant ethoxylated lauryl ether (Ultrol L70) was used to stabilize the nanoemulsions. The surfactant concentrations were varied from 10 to 12 wt% and the oil phase from 5 to 20 wt%. The efficiency of extraction of oil from sand was assessed using the two nanoemulsions that presented the greatest stability (containing 5 wt% oil phase with 12 wt% surfactant and 20 wt% oil phase with 10 wt% surfactant). A 2(3) factorial experimental design with center point was used to evaluate and improve the soil washing process, varying the time, temperature and agitation speed of the system. The highest efficiencies were obtained at 45 degrees C.

Nanoemulsions as delivery systems for lipophilic drugs.

Nanoemulsions have received a growing attention as colloidal drug carriers for pharmaceutical applications. Their advantages over conventional formulations include drug enhanced solubility and bioavailability, protection from toxicity, improved pharmacological activity and stability, more sustained delivery and protection from physical and chemical degradation. Nanoemulsions can be prepared by two major techniques, high-energy and low-energy emulsification. Both these emulsification methods have proved to be efficient to obtain stable nanoemulsions with small and highly uniform droplets. Further research into nanoemulsions is important to develop novel liquid formulations with more efficient results in therapeutic.

Stability of orange oil/water nanoemulsions prepared by the PIT method.

This article reports the preparation and characterization of orange oil/water nanoemulsions stabilized by commercial nonionic surfactants based on ethoxylated lauryl ether (Ultrol line), by the phase inversion temperature (PIT) method. The orange oil/surfactant/water dispersions were prepared at different HLB values, by varying the concentrations of the surfactants as well as the concentration of the oil phase. The stability of the o/w nanoemulsions and the size distribution of the dispersed particles in these systems in general depended on the concentration of the oil phase used: the emulsions prepared with an oil phase of 14 wt% had smaller droplet size in the dispersed phase than the emulsions prepared in the presence of oil phases of 20 and 30 wt%. The nanoemulsions prepared with pure surfactants were more stable in the presence of Ultrol L60, but the surfactants' cloud point had a strong influence on the stability of the emulsions formed when this was very near room temperature. Because of this, we prepared systems containing mixtures of surfactants. Among these systems, the most stable nanoemulsions were those prepared with a Ultrol L100/Ultrol L20 mixture with HLB of 12.40. This behavior can be attributed to the complete solubilization in mixed micelles of the more hydrophobic surfactant.

Influence of the hydrotrope structure on the physical chemical properties of polyoxide aqueous solutions.

The physical chemical properties of block substituted poly(ethylene oxide-propylene oxide) (PEO-PPO) block copolymer aqueous solutions were evaluated in the presence of two hydrotropes of different structures: sodium p-toluene sulfonate (NaPTS) and butyl monoglycol sodium sulfonate (NaBMGS). The critical micelle concentration and the cloud point of the copolymer solutions were displaced to higher concentration values, indicating that the solubility of the copolymer was increased in the presence of the hydrotropes. Temperature increased the micelle hydrodynamic radius, but concentration had a limited effect. Carbon-13 nuclear magnetic resonance (13C NMR) permitted the interaction between the surface-active agent and the hydrotrope to be evaluated: NaBMGS, which presented a more pronounced hydrotropic effect, interacts more effectively with the hydrophobic moiety of the surfactant, while NaPTS interacts rather mainly with the hydrophilic oxyethylenic groups. The results furnish experimental evidence to conclude that the hydrotropic phenomenon is specific in relation to both the hydrotrope and the solubilizate.

PLURONIC x TETRONIC polyols: study of their properties and performance in the destabilization of emulsions formed in the petroleum industry.

In this work, a new family of branched poly(ethylene oxide-propylene oxide) (PEO-PPO) block copolymers designed as TETRONIC polyols is evaluated and compared to linear PEO-PPO block copolymers designed as PLURONIC polyols. Additives have been employed as well in order to improve solubility of these materials in aqueous solution. Such additives include the sodium p-toluene sulfonate (NaPTS) hydrotrope and concentrated hydrochloric acid. Solubility tests and aqueous solution surface tension data showed consistent results: the structure of the block PEO-PPO copolymers exerts a huge influence on their solubility in water. The solubility of such copolymers is increased by the presence of the sodium toluene sulfonate (NaPTS) hydrotrope. The presence of HCl caused increased solubility for the copolymer TETRONIC polyol only, the effect being less than that observed for the hydrotrope. It is concluded that as regards emulsion stabilization, TETRONIC copolymer polyols perform better. Correlation between structure and properties leads to the optimization of block PEO-PPO copolymer selection aiming at using these materials for the separation of petroleum industry emulsions.