0000000001091170
AUTHOR
Ali Assifaoui
Drug release from calcium and zinc pectinate beads: Impact of dissolution medium composition
The aim of this study was to investigate drug release from calcium and zinc pectinate beads and to understand the impact of medium electrolytes during drug transfer. A potential drug carrier for colonic drug delivery (rutin) was prepared with calcium and zinc pectinate beads and was tested in three different simulated intestinal fluids (pH 7.3) with phosphates (Sorensen’s and Mc Ilvaine’s buffers) and without phosphates (Tris-buffer). According to swelling studies and zinc ions release, it was showed that zinc ions keep adhering to the bead surface. Drug release and swelling behaviour from the two dosage forms depend not only on pH and ionic strength but also on the electrolytes there were …
Thermal Denaturation of Pea Globulins (Pisum sativum L.)—Molecular Interactions Leading to Heat-Induced Protein Aggregation
The heat-induced denaturation and aggregation of mixed pea globulins (8%, w/w) were investigated using differential scanning calorimetry (DSC), SDS-PAGE, and size-exclusion chromatography (SEC-HPLC). DSC data showed that the pea proteins denaturation temperature (T(d)) was heating-rate dependent. The T(d) value decreased by about 4 °C by lowering the heating rate from 10 to 5 °C/min. The SDS-PAGE analysis revealed that protein denaturation upon heating at 90 °C was mainly governed by noncovalent interaction. The SEC-HPLC measurements indicated that low-denatured legumin (≈350-410 kDa) and vicilin/convicilin (≈170 kDa) globulins were heat-denatured and most of their subunits reassociated int…
Silica-coated calcium pectinate beads for colonic drug delivery
The aim of this work is to develop novel organic-inorganic hybrid beads for colonic drug delivery. For this purpose, calcium pectinate beads with theophylline are prepared by a cross-linking reaction between amidated low-methoxyl pectin and calcium ions. The beads are then covered with silica, starting from tetraethyoxysilane (TEOS), by a sol-gel process. The influence of TEOS concentration (0.25, 0.50, 0.75 and 1.00 M) during the process is studied in order to modulate the thickness of the silica layer around the pectinate beads and thus to control the drug release. The interactions between the silica coating and the organic beads are weak according to the physicochemical characterizations…
Structure of calcium and zinc pectinate films investigated by FTIR spectroscopy
International audience; Calcium and zinc pectinate gels were prepared using a method which allowed calcium or zinc to diffuse from the cross-linking solution through a dialysis membrane to form a gel with amidated low-methoxyl pectin. The gel thus obtained was then dried, and the film structure was studied using FTIR spectroscopy as a function of the cation content (0%, 5%, 10%, and 15% w/v). Important consideration was given to the three functional groups (amide, carboxyl ester, and carboxylate groups) present in the pectin. When the zinc content was increased, the three wavenumber values corresponding to these three functional groups did not change significantly, while for calcium pectina…
Effect of pea proteins extraction and vicilin/legumin fractionation on the phase behavior in admixture with alginate
Abstract Soluble and natural mixed pea proteins (PP) were extracted from defatted pea seeds according to acidic precipitation (PPP) or ultrafiltration/diafiltration (PPDF) procedures. The isolates contained proteins with a low level of denaturation. Mixed pea globulins isolates presented quite similar solubility and thermal profiles, also a similar polypeptide composition. Vicilin/convicilin 7S (Vic) and legumin 11S (Leg) fractions were obtained by batch chromatography using a salt gradient for the elution. Several incompatible systems were built by mixing the pea proteins with an anionic polysaccharide (sodium alginate, SA), when biopolymers were both negatively charged. Most of mixtures e…
Protein aggregation induced by phase separation in a pea proteins–sodium alginate–water ternary system
Abstract The physicochemical properties of a native, globular plant protein–linear anionic polysaccharide aqueous system at 20 °C were investigated in conditions where biopolymers carry a net negative charge (pH 7.2, 0.1 M NaCl). The pea proteins–sodium alginate mixtures showed a phase separation mainly by thermodynamic incompatibility, characterized at both the macroscopic and microscopic scale. Phase diagram was established and confocal laser scanning microscopy (CLSM) provided accurate data on the microstructure morphology of the system, regarding its phase behavior. In admixture, sodium alginate induced a protein aggregation, certainly by a local depletion of the polysaccharide. Protein…
Controlled release of tyrosol and ferulic acid encapsulated in chitosan–gelatin films after electron beam irradiation
Abstract This work deals with the study of the release kinetics of antioxidants (ferulic acid and tyrosol) incorporated into chitosan–gelatin edible films after irradiation processes. The aim was to determine the influence of electron beam irradiation (at 60 kGy) on the retention of antioxidants in the film, their release in water (pH=7) at 25 °C, in relation with the barrier and mechanical properties of biopolymer films. The film preparation process coupled to the irradiation induced a loss of about 20% of tyrosol but did not affect the ferulic acid content. However, 27% of the ferulic acid remained entrapped in the biopolymer network during the release experiments whereas all tyrosol was …
Controlled loading and release of beta-lactoglobulin in calcium-polygalacturonate hydrogels
International audience; We show here how the structure of polygalacturonate (polyGalA) hydrogels cross-linked by Ca2+ cations via external gelation controls the loading and the release rate of betalactoglobulin (BLG), a globular protein. Hydrogels prepared from a polyGalA/BLG solution are found similar to those obtained from a polyGalA solution in our previous study (Maire du Poset, et al. Biomacromolecules 2019, 20(7), 2864-2872): they exhibit similar transparencies and gradients of mechanical properties and polyGalA concentration. The nominal BLG/polyGalA ratio of the mixtures is almost recovered within the whole mixed hydrogel despite such strong concentration gradients, except in the pa…
Structural studies of adsorbed protein (betalactoglobulin) on natural clay (montmorillonite)
International audience; In this work, the adsorption of a small globular protein (betalactoglobulin, BLG), on a natural montmorillonite clay (Mt) was investigated in acidic buffer (pH = 3). The combination of different characterization techniques such as zetametry, X-ray diffraction, transmission electronic microscopy, fluorescence and solid state nuclear magnetic resonance spectroscopies shed light on the interaction mechanism between the clay mineral and the proteins. For low BLG concentration, a slight increase of the interlayer spacing of the clay mineral was noticed as well as structural changes of the protein. In contrast, as the concentration of BLG increased, the adsorption led to a…
Dielectric spectroscopy measurements of the sub-Tg relaxations in amorphous ethyl cellulose: A relaxation magnitude study
Amorphous ethyl cellulose exhibits three secondary relaxations at temperatures below its glass transition. The fitted parameters that describe these processes and the comparison with other polysaccharides allow to ascribe the relaxations to lateral groups on one hand and to local main chain motion on the other hand. Their contributions to the dielectric constant overlap and induce a broad dielectric losses peak. The amplitude of one of these relaxations is found to decrease regularly with time. It is believed it comes from a gradual change of the polar groups chemical environment that constrains their motion.
The effects of sodium alginate and calcium levels on pea proteins cold-set gelation
Abstract A multi-scale investigation of pea proteins – alginate cold-set gels was proposed in this study. The gel preparation followed a two-steps procedure. Globular pea proteins were first denatured and aggregated by a pre-heating step. Sodium alginate was then added at different concentrations. Thereafter the in situ gelation process was induced at 20 °C using glucono-δ-lactone (GDL) and two calcium carbonate (CC) levels; calcium cations were released as the pH decreased. Small-amplitude rheology measurements (storage modulus G′) showed that stronger mixed gels were obtained than single-biopolymer solutions. Confocal laser scanning microscopy (CLSM) revealed phase-separating microstructu…
Tuning the Structure of Galacturonate Hydrogels: External Gelation by Ca, Zn, or Fe Cationic Cross-Linkers
International audience; We show here how the nature of various divalent cations M2+ (Ca2+, Zn2+, or Fe2+) influences the structure and mechanical properties of ionotropic polygalacturonate (polyGal) hydrogels designed by the diffusion of cations along one direction (external gelation). All hydrogels exhibit strong gradients of polyGal and cation concentrations, which are similar for all studied cations with a constant ratio R = [M2+]/[Gal] equal to 0.25, showing that every M2+ cation interacts with four galacturonate (Gal) units all along the gels. The regions of the hydrogels formed in the early stages of the gelation process are also similar for all cations and are homogeneous, with the s…
Interactions between proteins, phytic acid and calcium in Fava Bean concentrate
Interactions between proteins, phytic acid and calcium in Fava Bean concentrate
Structural behaviour differences in low methoxy pectin solutions in the presence of divalent cations (Ca 2+ and Zn 2+ ): a process driven by the binding mechanism of the cation with the galacturonate unit
International audience; In this paper, we compare the interactions between low methoxy pectin (LMP) and either Ca2+ or Zn2+ in semi-dilute solutions. Intrinsic viscosity and turbidity measurements reveal that pectin-calcium solutions are more viscous, but yet less turbid, than pectin-zinc ones. To get a molecular understanding on the origin of this rather unexpected behavior, we further performed isothermal titration calorimetry, small angle neutron scattering experiments, as well as molecular dynamics simulations. Our results suggest that calcium cations induce the formation of a more homogeneous network of pectin than zinc cations do. The molecular dynamics simulations indicate that this …
Pellets based on polyuronates: Relationship between gelation and release properties
International audience; Three polyuronates: amidated low methoxyl pectin (ALMP), low methoxyl pectin (LMP) and polygalacturonic acid (PGA) were used to encapsulate rutin in pellets, and they were characterized by different techniques (macroscopic properties, Calcium and rutin release). The ability of the three polyuronates to bind calcium ions and the viscoelastic properties of gels were performed to relate the properties of the pellets to the gel structures. The pellets size, the water content, the water uptake, the release of calcium and rutin varied depending on the polyuronate used. The pellets size of ALMP were smaller than LMP and PGA with a lower water content, but this matrix was mo…
Influence of low methoxyl pectin gel textures and in vitro release of rutin from calcium pectinate beads.
This study described the preparation and characterization of low methoxyl pectin (LMP) gels and beads for controlled release applications. The rheological characterization of the various formulations was proposed. Then the mechanical and morphological characterizations of beads were determined. Finally, the controlled release studies taking rutin as a model drug was evaluated. The results showed that Young's modulus values of non-amidated LMP gels decrease when adding up to 15% sorbitol. Calcium pectinate beads loaded with rutin are about 600 μm, oblong shaped with dense matrix. Beads containing sodium bicarbonate showed about 80% lower rutin encapsulation efficiency by increasing the pH of…
Pectin as Drug-Release Vehicle
Pectin as a natural biopolymer is extensively used for pharmaceutical and biomedical applications, essentially due to its gelling properties that could be influenced by pectin sources and extraction methods. This chapter focuses on an overview of pectin drug delivery systems classified by their administration routes. Oral drug delivery systems have been mainly developed, as pectin could be used in tablets as binder or matrix excipients and in microparticles/beads obtained by ionotropic gelation. The main objective is to target the colon, as pectin is resistant in acidic pH and sensitive to pectinolytic enzymes in the colon. To obtain suitable properties, pectin could be used in its native s…
How Accurate Is the Egg-Box Model in Describing the Binding of Calcium to Polygalacturonate? A Molecular Dynamics Simulation Study
We performed molecular dynamics (MD) simulations of octameric galacturonate, GalA8, chains in the presence of Ca2+ in a ratio of R = [Ca2+]/[GalA] = 0.25 in order to determine to which extent the popular "egg-box model" (EBM) is able to describe the association between Ca2+ cations and polygalacturonate (polyGalA) chains. To this aim, we slig h t l y revised the empirical parameters for the interaction between Ca2+ and the carboxylate oxygen atoms of GalA units so as to reproduce the experimental Ca2+-GalA association constant. We also defined an ad hoc order parameter, referred to as the egg-box score (EBS), that quantifies any deviation of the local coordination geometry of calcium cation…