Maslinic acid solid lipid nanoparticles as hydrophobic anticancer drug carriers: Formulation, in vitro activity and in vivo biodistribution.

Maslinic acid (MA) is a natural pentacyclic triterpenoid with inherent antitumor activity which has a very low solubility in water. MA solid lipid nanoparticles (SLNs) were prepared using Poloxamer 407 and Dicarboxylic acid-Poloxamer 407 as surfactants. Both MA SLNs are monodisperse, with sizes around 130 nm, and stable. Curcumin has been encapsulated in both types of nanoparticles without altering their colloidal properties. Moreover, SLNs greatly improve the solubility of MA and Curcumin. The cytotoxicity of MA and SLNs has been evaluated in BxPC3 human pancreatic cancer cells, MCF7 human breast cancer cells, and in a human fibroblast primary cell line. MA shows higher cytotoxic effect in BxPC3 and MCF7 cancer cells than in human primary fibroblasts. Nile Red loaded MA SLNs are quickly uptaken by BxPC3 and MCF7 cells, and show different cytoplasmic distributions depending on the cellular line. The oral or intravenous administration of MA SLNs in mice does not report any toxic effect, and the intravenous administration of fluorescent MA SLNs shows a homogeneous distribution in mice, without site-specific accumulation. Results suggest the great potential of MA SLNs as nanocarriers of anticancer drugs and as promising targeted theranostic nanodevices.

Interactions between curcumin and cell membrane models by Langmuir monolayers.

Studying interactions between potential anticancer drugs and cell membrane models is of great interest to explore the capability of novel drugs in the development of anticancer treatments. Lipid membrane models are useful to understand cellular interactions and to discern drug mechanism action. Here, the interactions of curcumin, as a bioactive natural compound with anti-cancer properties, with both healthy and cancerous or tumor cell membrane models, based on Langmuir monolayers, have been studied. The healthy-cell membrane model is composed of cholesterol 67%, and saturated lipid dipalmitoylphosphatidylcholine 33%. The cancerous-cell-membrane-model is composed of a lower proportion of cholesterol, 25%, and unsaturated lipid sphingomyelin 75%. To compare their interaction with curcumin we report the compression isotherms registered for both lipid membrane models and curcumin in different proportions, their compression moduli and the thermodynamic interaction parameters. From this analysis, we evidence a destabilizing interaction between curcumin and the cancerous cell membrane model in comparison with the healthy one. This interaction is further visualized by micro-Brewster Angle and Atomic Force Microscopies. Our experiments show that the drug enhances cohesion in the healthy membrane model whereas it fluidifies the cancerous cell membrane model causing thermodynamic destabilization. These are useful results to improve the selectivity of the drug avoiding adverse side effects of most current anticancer therapies.

Solid lipid nanoparticles to improve bioaccessibility and permeability of orally administered maslinic acid.

Maslinic acid (MA) is a plant-derived, low water-soluble compound with antitumor activity. We have formulated MA in the form of solid lipid nanoparticles (SLNs) with three different shell compositions: Poloxamer 407 (PMA), dicarboxylic acid-Poloxamer 407 (PCMA), and HA-coated PCMA (PCMA-HA). These SLNs improved the solubility of MA up to 7.5 mg/mL, are stable in a wide range of pH, and increase the bioaccessibility of MA after in vitro gastrointestinal (GI) digestion. Gastrointestinal digested SLNs afforded MA delivery across in vitro gut barrier models (21 days old Caco-2 and mucus-producing Caco-2/HT29-MTX co-cultures). The cellular fraction of Caco-2/HT29-MTX co-cultures retained more MA from GI digested PCMA-HA than the Caco-2 monolayers. The concentration of MA reached in the basolateral chamber inhibited growth of pancreatic cancer cells, BxPC3. Finally, confocal microscopy images provided evidence that Nile Red incorporated in MA SLNs was capable of crossing Caco-2 monolayers to be taken up by basolaterally located BxPC3 cells. We have demonstrated that SLNs can be used as nanocarriers of hydrophobic antitumor compounds and that these SLNs are suitable for oral consumption and delivery of the bioactive across the gut barrier.

Hyaluronic acid and human/bovine serum albumin shelled nanocapsules: Interaction with mucins and in vitro digestibility of interfacial films.

Liquid lipid nanocapsules are oil droplets surrounded by a protective shell, which enable high load and allow controlled delivery of lipophilic compounds. However, their use in food formulations requires analysing their digestibility and interaction with mucin. Here, serum albumins and hyaluronic acid shelled olive oil nanocapsules are analysed to discern differences between human and bovine variants, the latter usually used as model system. Interfacial interaction of albumins and hyaluronic acid reveals that human albumin presents limited conformational changes upon adsorption, which increase by complexation with the polysaccharide present at the interface. The latter also promotes hydrophobic interactions with mucin, especially at pH 3 and protects albumin interfacial layer under in vitro gastric digestion. The interfacial unfolding induced in human albumin by hyaluronic acid facilitates in vitro lipolysis while its limited conformational changes provide the largest protection against in vitro lipolysis.

Preparation of highly stable oleogel-based nanoemulsions for encapsulation and controlled release of curcumin.

Oleogels have been proposed as suitable systems for the encapsulation and delivery of lipophilic bioactive compounds. This work aimed to produce stable nanoemulsions of gelled-oil particles using monoglyceride (MG) oleogels loaded with curcumin. High-speed homogenization followed by ultrasonication was used for obtaining colloidal dispersions. The effects of ultrasonication processing parameters and formulation were evaluated to optimize particle size, polydispersity index (PDI), and stability during storage. All sonication parameters had a significant effect on particle size and PDI. A Pluronic F-68 + Tween 80 surfactant mixture with the lowest oleogel/aqueous phase ratio (5/95) produced nanoemulsions which were at least 10-month stable. The nanoemulsions showed a higher encapsulation efficiency than the sample without the gelator (73.85-91.05% vs. 56.99%). Furthermore, it was corroborated that structuring oil particles with MG crystals produces a matrix that entraps curcumin molecules and slows down their release. These findings provide useful information for the development of new nutraceutical products.

Applications of serum albumins in delivery systems: Differences in interfacial behaviour and interacting abilities with polysaccharides.

One of the major applications of Serum Albumins is their use as delivery systems for lipophilic compounds in biomedicine. Their biomedical application is based on the similarity with Human Serum Albumin (HSA), as a fully biocompatible protein. In general, Bovine Serum Albumin (BSA) is treated as comparable to its human homologue and used as a model protein for fundamental studies since it is available in high amounts and well understood. This protein can act as a carrier for lipophilic compounds or as protective shell in an emulsion-based vehicle. Polysaccharides are generally included in these formulations in order to increase the stability and/or applicability of the carrier. In this review, the main biomedical applications of Albumins as drug delivery systems are first presented. Secondly, the differences between BSA and HSA are highlighted, exploring the similarities and differences between these proteins and their interaction with polysaccharides, both in solution and adsorbed at interfaces. Finally, the use of Albumins as emulsifiers for emulsion-based delivery systems, concretely as Liquid Lipid Nanocapsules (LLNs), is revised and discussed in terms of the differences encountered in the molecular structure and in the interfacial properties. The specific case of Hyaluronic Acid is considered as a promising additive with important applications in biomedicine. The literature works are thoroughly discussed highlighting similarities and differences between BSA and HSA and their interaction with polysaccharides encountered at different structural levels, hence providing routes to control the optimal design of delivery systems.

Effect of Hyaluronic Acid and Pluronic-F68 on the Surface Properties of Foam as a Delivery System for Polidocanol in Sclerotherapy.

The use of foams to deliver bioactive agents and drugs is increasing in pharmaceutics. One example is the use of foam as a delivery system for polidocanol (POL) in sclerotherapy, with the addition of bioactive compounds to improve the delivery system being a current subject of study. This work shows the influence of two bioactive additives on the structure and stability of POL foam: hyaluronic acid (HA) and Pluronic-F68 (F68). HA is a natural non-surface-active biopolymer present in the extracellular matrix while F68 is a surface-active poloxamer that is biocompatible with plasma-derived fluids. Both additives increase the bulk viscosity of the sample, improving foam stability. However, HA doubled and F68 quadruplicated the foam half lifetime of POL. HA reduced the size and polydispersity of the bubble size distribution and increased the surface elasticity with respect to POL. Both facts have a positive impact in terms of foam stability. F68 also altered bubble structure and increased surface elasticity, again contributing to the enhancement of foam stability. The surface characterization of these systems is important, as in foam sclerotherapy it is crucial to assure the presence of POL at the surface of the bubbles in order to deliver the sclerosant agent in the target vein.

Effects of cooling temperature profiles on the monoglycerides oleogel properties: A rheo-microscopy study.

The oleogelation process has become in a great interest area for the food sector. The aim of this study was to understand the effect of cooling temperature profiles (CTP) applied during oleogelation on microstructure and some macroscopic properties of monoglycerides (MG) oleogels. To this purpose, oleogels from MG and high oleic sunflower oil were produced using programed CTP corresponding to the actual temperature evolution of the samples when they are left at rest to progress in a specific ambient temperature (AT). In order to evaluate the crystal formation during the gelation process, a torsional rheometer equipped with a rheo-microscope (RM) module was used. This allowed us to carry out simultaneously rheological measurements and record images of the gels during their formation process. Overall, microstructural characteristics were determined: fractions of crystalline material and oil, crystal length and shape, the Avrami index, and the fractal dimension. Although crystal formation took place during a similar range of temperatures (~55-46 °C), significant morphological differences in the distribution and size of crystal and aggregates were observed depending on the applied CTP, and the area occupied by the crystals and oil phase did not depend on CTP used. RM images were useful to follow the kinetics of crystallization as well as to identify a more restricted time domain in the rheological behavior allowing to find more accurate Avrami index values. Furthermore, the analysis of RM images turned out to be an efficient approach to obtain accurate measurements of the fractal dimension. High fractal dimension values were associated with gels exhibiting high number of homogeneous small crystals. Oleogels composed by this network generated a material with high capacity to retain oil. A weak-link regime approach applied to the dynamic systems was appropriate to describe the relationship between the elastic modulus and the crystal formation during the oleogels structuration. In conclusion, these findings may serve to the food industry to achieve a better understanding of the oleogelation process that allows it to control the quality of obtained oleogels, which could be utilized to replace and/or reduce the trans and saturated fats in food formulations.

Different approaches to study protein films at air/water interface.

In this review classical studies on insoluble liquid monolayers formed by proteins are examined and compared. It has been focused the attention on the information that it is possible to obtain from the π-a isotherms recorded by compression of the monolayers. In recent decades new techniques have developed, mainly microscopy, that provide valuable information on the behavior and structure of fluid films. However, frequently the data are difficult to interpret and require a previous thermodynamic study of them on the basis of the surface tension (or surface pressure) as a function of the molecular area measurement. The main aim of this paper is to underline that surface balance type of Langmuir is a powerful technique since it enables to obtain information at molecular level from a macroscopic analysis. Notably, this information is revealed very interesting when it comes to studying protein films. From this point of view it has been reviewed the study methods and results for four proteins.

Natural Inhibitors of Lipase: Examining Lipolysis in a Single Droplet.

Inhibition of lipase activity is one of the approaches to reduced fat intake with nutritional prevention promoting healthier diet. The food industry is very interested in the use of natural extracts, hence reducing the side effects of commercial drugs inhibiting lipolysis. In this work we propose a novel methodology to rapidly assess lipolysis/inhibition in a single droplet by interfacial tension and dilatational elasticity. The evolution of the interfacial tension of lipase in simplified duodenal fluid in the absence and that in the presence of the pharmaceutical drug Xenical are the negative (5 ± 1 mN/m) and positive (9 ± 1 mN/m) controls of the inhibition of lipolysis, respectively. Then, we correlate the inhibition with the reduction of the interfacial activity of lipase and further identify the mode of action of the inhibition based on dilatational response (conformational changes induced in the molecule/blocking of adsorption sites). This work provides new insight into the lipase inhibition mechanism and a rapid methodology to identify the potential of new natural inhibitors.

Block copolymers at interfaces: interactions with physiological media.

Triblock copolymers (also known as Pluronics or poloxamers) are biocompatible molecules composed of hydrophobic and hydrophilic blocks with different lengths. They have received much attention recently owing to their applicability for targeted delivery of hydrophobic compounds. Their unique molecular structure facilitates the formation of dynamic aggregates which are able to transport lipid soluble compounds. However, these structures can be unstable and tend to solubilize within the blood stream. The use of nanoemulsions as carriers for the lipid soluble compounds appears as a new alternative with improved protection against physiological media. The interfacial behavior of block copolymers is directly related to their peculiar molecular structure and further knowledge could provide a rational use in the design of poloxamer-stabilized nanoemulsions. This review aims to combine the new insights gained recently into the interfacial properties of block copolymers and their performance in nanoemulsions. Direct studies dealing with the interactions with physiological media are also reviewed in order to address issues relating metabolism degradation profiles. A better understanding of the physico-chemical and interfacial properties of block copolymers will allow their manipulation to modulate lipolysis, hence allowing the rational design of nanocarriers with efficient controlled release.