Improvement of an encapsulation process for the preparation of pro- and prebiotics-loaded bioadhesive microparticles by using experimental design.

The purpose of this study was to design a new vaginal bioadhesive delivery system based on pectinate-hyaluronic acid microparticles for probiotics and prebiotics encapsulation. Probiotic strains and prebiotic were selected for their abilities to restore vaginal ecosystem. Microparticles were produced by emulsification/gelation method using calcium as cross-linking agent. In the first step, preliminary experiments were conducted to study the influence of the main formulation and process parameters on the size distribution of unloaded microparticles. Rheological measurements were also performed to investigate the bioadhesive properties of the gels used to obtain the final microparticles. Afterwards an experimental design was performed to determine the operating conditions suitable to obtain bioadhesive microparticles containing probiotics and prebiotics. Experimental design allowed us to define two important parameters during the microencapsulation process: the stirring rate during the emulsification step and the pectin concentration. The final microparticles had a mean diameter of 137µm and allowed a complete release of probiotic strains after 16h in a simulated vaginal fluid at +37°C.

Evaluation of gliadins nanoparticles as drug delivery systems: a study of three different drugs.

In this paper, biopolymer nanoparticles are studied, which unlike many synthetic carriers used for controlled release, are biocompatible and biodegradable systems. Gliadins nanoparticles are obtained by a desolvatation method, also known as drawning-out precipitation. These particles have been shown to be interesting as drug release systems for all-trans-retinoic acid. The aim of this paper was to study the influence of the polarity of different drugs on nanoparticle characteristics such as size and drug loading efficiency. Three drugs of three different polarities were studied: the hydrophobic Vitamin E (VE), the slightly polar mixture of linalool and of linalyl acetate (LLA) and the cationic amphiphilic benzalkonium chloride (BZC). This comparative work shows that the amount of the entrapped VE and LLA is higher than that of the cationic BZC, confirming a strong interaction between gliadins and apolar compounds, due to the apolarity of the proteins. This interaction results in a low diffusion coefficient and a partition coefficient in favour of gliadins, resulting in a low permeability coefficient. The drug release kinetics of two substances, LLA and BZC, are observed, in showing a burst effect, then a diffusion process, which can be modelled assuming that the particles are homogeneous spheres.

Biopolymeric colloidal carriers for encapsulation or controlled release applications.

Biopolymers represent an interesting alternative to synthetic polymers in order to be used as structured carriers for controlled release and encapsulation applications. In particular, the ability of these carriers to entrap both hydrophilic and hydrophobic drugs may be very promising for many applications. In addition, the absence of chemical compounds and organic solvents used to produce biopolymeric matrices could be very interesting for some industrial applications. Simple or complex coacervation methods involving proteins or protein and polysaccharide mixtures were used to create new matrices dedicated to controlled release applications. Controlled release experiments with model compounds were conducted in order to evaluate the performance of such matrices. An alternative and promising research field deals with particles obtained from hydrogel systems. Totally transparent solid matrices resulting from the dehydration of new protein gels were formed and swelling capacities of these matrices were studied.

Alpha-tocopherol encapsulation and in vitro release from wheat gliadin nanoparticles.

Alpha-tocopherol, or vitamin E (VE), is widely used as a strong antioxidant in many medical and cosmetic applications, but is rapidly degraded, because of its light, heat and oxygen sensitivity. Thus, all of its formulation has to avoid contact with light, heat or air. Drug loaded carriers are an attractive opportunity, especially if they are made for bioacceptable macromolecules such as vegetal proteins. For instance, gliadins, extracted from wheat gluten, generate nanoparticles by a desolvatation method and may interact with epidermal keratin for therapeutic or cosmetic formulations. Their lipophilic drug loading capacities have been investigated. The VE loaded gliadin nanoparticles have been characterized by their size, by their zeta potential, by their VE payload, and by their entrapment efficiency. When VE loaded, the gliadin particle size is approximately 900 nm and their charge is close to zero. They are suitable VE drug carriers with an optimum encapsulation rate approximately 100 VE microg/gliadin mg with an efficiency of more than 77%. The release behaviour of VE loaded nanoparticles may be interpreted as a 'burst effect', followed by a diffusion process through an homogeneous sphere.

[Wheat gliadin nanoparticle size control by determination of the solubility parameters of these plant proteins]. / Maîtrise de la taille de nanoparticules de gliadines de blé par la détermination de leur paramètre de solubilité.

Gliadins nanoparticles, protein complex from wheat gluten, were prepared by coacervation (macromolecules desolvatation). The objective was to prepare nanometric colloidal systems whith both smallest particle size and polidispersity index. Macromolecules solvent choice is predominant. Their total solvatation enables of control the desolvatation process and thence particle sizes. Different pharmaceutical solvents were assayed. In order to select the best of them, a thermodynamical approach was used. It rests on the determination of the solubility parameter delta G of the gliadins complex. The best solvent is the one whose solubility parameter (calculated or experimentally determined) is equal to the plant protein's.

Vesicles and particles of sodium bis(2-ethylhexyl) phosphate in binary and ternary systems.

Vesicles were identified in aqueous solution of pure sodium bis(2-ethylhexyl) phosphate, a short branched chain surfactant. Superficial tension measurements show that the vesicles appear above a molality of 0.02 (0.69 %w). These aggregates are equilibrium structures. The "packing parameter' theory established by Israelachvili et al. allows the prediction of the occurrence of such vesicles. If an organic solvent, such as xylene or ethylhexanoate, is added to the binary system, a different type of aggregate appears, the size of which is determined by several methods including electron microscopy and light scattering. Interfacial tension measurements show that these aggregates would be expected to form above a molality of 0.02. According to our experimental results, the microstructure of these aggregates can be described as micelles and/or vesicles, swollen or not.