Data supporting the physico-chemical characterization, cellular uptake and cytotoxicity of lipid nanocapsules.

The aim of this data article is to provide data for a basic knowledge of the properties of lipid nanocapsules, a new colloidal system with very promising applications in drug delivery. Firstly, we pay attention on how it is possible to determine their surface composition by means of electrokinetics measurements. On the other hand, we provide experimental evidences for a better understanding of the factors that determine the interactions of these nanoparticles with cells as a necessary step to guide the design of the most effective formulations. Additionally, we supply information about encapsulation efficiency of docetaxel, a potent chemotherapy drug, inside nanocapsules supporting the experimental cytotoxicity results of these nanosystems.

Balancing the effect of corona on therapeutic efficacy and macrophage uptake of lipid nanocapsules.

Several studies have shown the potential of biocompatible lipid nanocapsules as hydrophobic drug delivery systems. Understanding the factors that determine the interactions of these oil-in-water nanoemulsions with cells is a necessary step to guide the design of the most effective formulations. The aim of this study was to probe the ability of two surfactants with a markedly different nature, a non-ionic poloxamer, and a charged phospholipid, to prepare formulations with shells of different composition and different surface properties. Thus we determined their effects on the interaction with biological environments. In particular, we investigated how the shell formulation affected the adsorption of biomolecules from the surrounding biological fluids on the nanocapsule surface (corona formation). A complete physicochemical characterization including an isothermal titration calorimetry (ITC) study revealed that the use of poloxamer led to nanocapsules with a marked reduction in the number of protein-binding sites. Surface hydrophilicity and changes in corona formation strongly correlated to changes in uptake by cancer cells and by macrophages. Our results indicate that the nature and concentration of surfactants in the nanocapsules can be easily manipulated to effectively modulate their surface architecture with the aim of controlling the environmental interactions, thus optimizing functionality for in vivo applications. In particular, addition of surfactants that reduce protein binding can modulate nanoparticle clearance by the immune system, but also screens the desired interactions with cells, leading to lower uptake, thus lower therapeutic efficacy. The two effects need to be balanced in order to obtain successful formulations.

Chitosan nanocapsules: Effect of chitosan molecular weight and acetylation degree on electrokinetic behaviour and colloidal stability.

In recent years, chitosan nanocapsules have shown promising results as carriers for oral drug or peptide delivery. The success in their applicability strongly depends on the stability of these colloidal systems passing through the digestive tract. In gastric fluids, clear stability comes from the high surface charge density of the chitosan shell, which is completely charged at acidic pH values. However, in the intestinal fluid (where the pH is almost neutral) the effective charge of these nanocapsules approaches zero, and the electrostatic forces cannot provide any stabilization. Despite the lack of surface charge, chitosan nanocapsules remain stable in simulated intestinal fluids. Recently, we have demonstrated that this anomalous stability (at zero charge) is owed to short-range repulsive forces that appear between hydrophilic particles when immersed in saline media. The present work examines the influence of the chitosan hydrophobicity, as well as molecular weight, in the stability of different chitosan nanocapsules. A study has been made of the size, polydispersity, electrophoretic mobility, and colloidal stability of eight core-shell nanocapsule systems, in which the chitosan-shell properties have been modified using low-molecular-weight (LMW) and high-molecular-weight (HMW) chitosan chains having different degrees of acetylation (DA). With regard to the stability mediated by repulsive hydration forces, the LMW chitosan provided the best results. In addition, contrary to initial expectations, greater stability (also mediated by hydration forces) was found in the samples formed with chitosan chains of high DA values (i.e. with less hydrophilic chitosan). Finally, a theoretical treatment was also tested to quantify the hydrophilicity of the chitosan shells.

Physicochemical Studies on the Interaction between N-Decanoyl-N-methylglucamide and Bovine Serum Albumin.

The protein-surfactant system constituted by bovine serum albumin (BSA) and N-decanoyl-N-methylglucamide (MEGA-10) has been studied by using surface tension, steady-state fluorescence, and dynamic light scattering measurements. It was found that the presence of protein delays the surfactant aggregation, which was interpreted as a sign of binding between surfactant and protein. Binding studies were carried out by two different methods. First, a treatment based on surface tension measurements was used to obtain information on the number of surfactant molecules bound per protein molecule under saturation conditions. Second, the binding curve for the BSA/MEGA-10 system was determined by examining the behavior of the intrinsic BSA fluorescence upon the surfactant addition. Both approaches indicate that the binding process is essentially cooperative in nature. The results of the aggregation numbers of MEGA-10 micelles, as well as those of resonance energy transfer from tryptophan residues to 8-anilinonaphthalene-1-sulfonate, corroborate the formation of micelle-like aggregates of surfactants, smaller than the free micelles, adsorbed on the protein surface. The dynamic light scattering results were not conclusive, in the sense that it was not possible to discriminate between protein-surfactant complexes and free micelles. However, the overall results suggest the formation of "pearl necklace" complexes in equilibrium with the free micelles of the surfactant.

Thermodynamics and micellar properties of tetradecyltrimethylammonium bromide in formamide-water mixtures.

The effect of formamide on the micellization of tetradecyltrimethylammonium bromide has been investigated by conductance and fluorescence probe experiments. The critical micelle concentration and the degree of counterion dissociation of micelles were obtained from conductance measurements in the temperature range of 20 to 40 degrees C. It was found that these two parameters increase with both temperature and formamide content in the solvent system. The thermodynamic parameters of micellization were estimated using the equilibrium model of micelle formation. The standard free energy of micellization was found to be negative in all cases and becomes less negative as the formamide content in the mixed solvent increases, but it is roughly independent of temperature. Although the entropic contribution was found to be larger than the enthalpy one, in particular at lower temperatures, an enthalpy-entropy compensation effect was observed for all systems. Micellar aggregation numbers were determined by the static quenching method, using pyrene as a probe and cetylpyridinium chloride as a quencher. The observed decrease in the micelle aggregation number, which is controlled by the increase in the surface area per headgroup, was attributed to an enhanced solvation in formamide rich solvent mixtures. Changes in the pyrene 1:3 ratio index, indicating a more polar environment, are consistent with an increased micellar solvation. Fluorescence polarization of both coumarin 6 and fluorescein are indicative of a decrease in microviscosity with cosolvent addition. The data on fluorescence anisotropy of coumarin 6 were analyzed using the wobbling in cone model. Data indicated the formation of micelles with a less ordered structure as the formamide increases in the solvent system.

Interaction of bacterial endotoxine (lipopolysaccharide) with latex particles: application to latex agglutination immunoassays.

The latex agglutination immunoassay technique uses polymer colloids as carriers for antibodies or antigens to enhance the immunological reaction. In this work, the interaction of a lipopolysaccharide (LPS) of Brucella Melitensis with two conventional latexes has been studied. Some experiments on the physical adsorption of the LPS onto these polystyrene beads have been performed and several complexes with different coverage degrees were obtained by modifying the incubation conditions. Regarding the application in the development of diagnostic test systems, it is advisable to study the latex-LPS complexes from an electrokinetic and colloidal stability point of view. The complexes were electrokinetically characterized by measuring the electrophoretic mobility under different redispersion conditions. The colloidal stability was determined by simple turbidity measurements. Experimental and theoretical data have been employed to study the molecular disposition of the LPS in the latex particle surface to compare with the outer membrane of bacterial cells. Latex complexes covered by different LPS amounts showed high colloidal stability and adequate immunoreactivity that remains for a long time period.