Abdesslem Ben Haj Amara

Characterization of hemoglobin immobilized in MgAl-layered double hydroxides by the coprecipitation method.

Hemoglobin was immobilized in Mg(2)Al-Layered Double Hydroxides (LDH) by coprecipation method at pH 9.0. Interactions between Hb and LDH particles were investigated by X-ray diffraction patterns, FTIR, UV-vis, circular dichroism, and fluorescence spectroscopies. Morphology and porosity of Mg(2)Al-Hb(cop) biohybrid are analyzed from SEM and TEM images and permeability measurement. The direct electron transfer of immobilized Hb was studied by cyclic voltammetry, and the electrocatalytic activity was evaluated at glassy carbon modified with this Mg(2)Al-Hb(cop) biohybrid. Even though the percentage of electroactive Hb was less than 2%, this bioelectrode showed a low detection limit (1.5 x 10(-8) M) and a very high sensitivity (37 A/M cm(2)) for the amperometric detection of H(2)O(2).

Preparation and optimization of a drug delivery system based on berberine chloride-immobilized MgAl hydrotalcite

Hydrotalcite (HT), also known as a layered double hydroxide (LDH) compound, has been widely used in past years in the formulation of drugs due to its specific properties including good biocompatibility, null toxicity, high chemical stability and pH-dependent solubility which aid in drug controlled release. In this work, berberine chloride (BBC) class antibacterial agent was immobilized into magnesium-aluminum LDH in order to improve the drug efficiency as well as to achieve the controlled release property. BBC molecules were immobilized into MgAl LDH through a conventional ion exchange reaction and co-precipitation method. The ion-exchange experiments of BBC on MgAl LDH were investigated with particular attention paid to the influence of the layer charge, the nature of the intercalated anion and the morphology. The immobilization efficiency was dependent upon the LDH properties and the immobilization process. Characterization by powder x-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and contact angle measurements revealed that the interaction of BBC with MgAl LDH occurs by adsorption rather than intercalation of BBC within LDH layers. In vitro anti-bacterial tests were carried out using disc diffusion assay to prove the effectiveness of these novel biohybrid beads as a controlled drug delivery method. Consequently, the BBC-LDH co-precipitated formulation revealed an enhanced anti-bacterial activity compared to the ion-exchanged formulation not only due to an improvement of chemical stability and retained amount of BBC molecules but also due to the release property.

Delivery system for berberine chloride based on the nanocarrier ZnAl-layered double hydroxide: Physicochemical characterization, release behavior and evaluation of anti-bacterial potential

Layered double hydroxide (LDH) has attracted major interest as one of the most versatile drug delivery systems especially for adsorption capacity and/or controlled delivery property of bioactive agents owing to their combining features of biohybrid. ZnAl synthesized layered double hydroxide can offer a platform to immobilize various types of bioactive compounds, particularly berberine chloride (BBC). However, the immobilization reaction of berberine chloride into ZnAl-LDH was performed by direct co-precipitation method at different ratios of BBC/LDH. BBC-ZnAl-LDH biohybrids were characterized in terms of structure, surface morphology, in vitro drug release profile and antibacterial assay against various bacterial cells. The BBC biomolecules were attached by coordinate bond. Structural and microstructural characterization confirms that interaction of BBC with ZnAl-LDH occurs by adsorption rather than intercalation of BBC within LDH layers. The BBC release profiles from BBC-ZnAl-LDH had a longer release duration compared to the physical mixture, and the drug release seemed faster with the low ratio of BBC/LDH. BBC-ZnAl-LDH can be internalized into bacterial cells. In vitro experiments in PBS medium showed that BBC-ZnAl-LDH biohybrid had higher cytotoxicity and inhibitory effects against three pathogenic bacteria; Staphylococcus aureus CIP 543154, Pseudomonas aeruginosa A22 and Bacillus subtilus ILP 1428B upon the drug release profiles and its destructive potential depends on the loading BBC on the LDH layers. Nonetheless these results prove that the prepared BBC-ZnAl-LDH biohybrids retain the anti-bacterial character of the BBC molecules and are therefore potential modified drug delivery system (DDS).

Adsorption of nisin into layered double hydroxide nanohybrids and in-vitro controlled release

Layered double hydroxide (LDH) nanohybrid intercalated biomolecules, including oligonecluotides, genes and peptides/proteins, have attracted particular attention since they exhibit improved safety and effectiveness as successful delivery biosystems. The current study specifically investigated the adsorption of nisin peptide and precisely the control of the release of the payload. Adsorption occurred from peptide solution in contact with zinc-aluminum LDH at room temperature, looking out over the influence of the Zn2+/Al3+ ratio, the anion exchange capacity, the nature of the intercalated anion, the host matrix, and the host morphology. Higher adsorption was obtained, around 80% of the loaded nisin and successful intercalation was verified by X-ray diffraction. The in-vitro release tests of the nisin from the biohybrid formulation was held over 25days in PBS medium (0.01M, pH7,4) and showed that no burst release phenomenon occurred at the beginning step, in addition, a sustained-time release of nisin was obtained compared with the free nisin. Therefore, these preliminary results are encouraging for the development of bioprotectors based on nisin intercalated LDH and being implemented in the food and medical industries.

Structure and antibacterial activity relationships of native and amyloid fibril lysozyme loaded on layered double hydroxide

Lysozyme from hen egg white is composed by a unique linear chain of 129 amino acids. It is known to inhibit Gram positive bacteria and to form amyloid fibrils at low pH, under 75°C. This work investigates the effect of the fibrillation and/or adsorption onto a layered double hydroxide material on the antibacterial properties of lysozyme. The kinetics of adsorption follows a behavior of pseudo second order model. The X-ray diffraction and the Fourier transform infrared spectroscopy highlight that adsorption occurs only on the external surface of the material. Interestingly, the amyloid fibrils of lysozyme retain their antibacterial properties when they are adsorbed on the layered double hydroxide; even if their activity is lowered, the active site of the enzyme is not fully denatured and is still accessible. This is confirmed by the study of the tryptophan using time-resolved fluorescence spectroscopy.

Quantitative XRD analysis of the dehydration–hydration performance of (Na+, Cs+) exchanged smectite

AbstractThe clay mineral membrane is increasingly used, as a natural geological barrier, in wastewater treatment. The variation of the environmental condition (T, P, RH, etc.) induces probably several change on the materials structure. This work aims at characterizing the link between dehydration–hydration behavior, charge location, and the ionic radius, in the case of dioctahedral smectites, exchanged with Na+ and Cs+ cation, which are occurred from industrial waste. A natural montmorillonite and beidellite, with different charge location (respectively, dioctahedral and trioctahedral), are selected. The exchange process is directed using Na+ and Cs+ cations. The hydration hysteresis is investigated “in situ” as a function of relative humidity condition rates. All samples are studied using quantitative X-ray diffraction (XRD) analysis. This method allows us to determine the structural parameters obtained from the theoretical mixed layer structure used to fit experimental XRD patterns. For both Na+ and/or ...

Structural and Electrochemical Properties of Cementitious and Hybrid Materials Based on Nacrite

This chapter gives possible valorization of a well-crystallized Tunisian nacrite as an interesting clay mineral belonging to the kaolin group: The first part of the chapter aims to produce a new synthetic material labeled ‘‘metanacrite”. Metanacrite is a supplementary cementitious material originated by heating a raw Tunisian nacrite at 823 K. The structure of the amorphous synthetic product was corroborated by X-ray diffraction (XRD) and infrared spectroscopy (IR). The decomposition of the silicate framework was confirmed by transmission electron microscope (TEM). The obtained metanacrite was also examined by electrochemical impedance spectroscopy (EIS). Accordingly, a semiconductor behavior of the novel synthetic material is evidenced. The second part of this chapter deals with the intercalation of lithium chloride salt between the planar layers of this Tunisian nacrite. The intercalation leads to a stable hybrid material that after calcination under inert atmosphere at 723–873 K induces an amorphous hybrid. The structural identification of the obtained nacrite–LiCl hybrid was determined by means of XRD, IR, TGA, and EIS. Finally, the resulting amorphous hybrid shows a superionic behavior with high ionic conductivity up to 10–2 S.m–1, good electrochemical stability, and can be used as an innovative solid electrolyte in lithium batteries and other electrochemical devices.

Synthesis, characterization and applications of a new nanohybrid composite: Nacrite/MgCl 2 .6H 2 O/ethanol

In this paper, we present an experimental study about the functionalization of a Tunisian nacrite with a hydrated magnesium chloride salt. The elaborated nanomaterial composite have been studied via X-ray diffraction, IR spectroscopy and EDXS. The quantitative XRD analysis allowed us to determine the structural parameters related to the number and position along the normal of the layers of the alkaline bivalent cations Mg2+, halide anions Cl- and water molecules in the interlamellar space. The obtained results showed that the basal spacing value shifted from 0.72 nm related to the unexpanded nacrite to 1.5 nm attributed to the nacrite/MgCl2.6H2O composite. The existence of intercalated water is verified by infrared spectroscopy, and revealed that the active groups on the nacrite layers and the intercalated species are linked by hydrogen bonds. Moreover, microstructure investigation by transmission electron microscopy (TEM) coupled with energy dispersive X-ray spectroscopy (EDXS) were carried out. TEM analyses confirm the intercalation of MgCl2.6H2O into the nacrite matrix. The main objective of this paper was to elucidate the influence of the new physicochemical properties of the modified nacrite layers that allows the evaluation of the applicability of this innovative composite material “nacrite/MgCl2.6H2O/ethanol”.

Removal of two anionic reactive textile dyes by adsorption into MgAl-layered double hydroxide in aqueous solutions

Textile dyes pose a significant challenge for water pollution due to the poor degradability of their complex aromatic structures (e.g., RR-120 and RBB-150). In order to minimize the harmful effects of RR-120 and RBB-150, the capacity of MgAl-layered double hydroxide for removing of these contaminants was studied herein. Batch adsorption experiments were conducted to investigate the effect of various operating parameters, such as solution pH, contact time, dye concentration, and temperature in order to provide optimal conditions for removal. Structural and morphological analyses were used to highlight the assembly and/or interaction LDH-dye. The state of equilibrium of RR-120 and RBB-150 adsorption was pH- and temperature-dependent and followed the pseudo-second-order rate model. Also, the equilibrium adsorption data of both dyes were found to adopt the Langmuir type isotherm model, which assumes a monolayer arrangement in LDH-dye. Furthermore, the effects of four major coexisting and competing mono- and divalent interlayer anions, such as NO3−, Cl−, CO32−, and SO42−, on the uptakes of RR-120 and RBB-150 were studied and the results showed that NO3− anions had insignificant effect on the uptakes of RR-120 and RBB-150 by MgAl. An equivalent study on the presence of both dyes in competitive trial adsorption/desorption from binary aqueous solution was investigated. And finally, the reuse operation of recovered material after dye adsorption was tested in up to 5 cycles of recyclability.

Nanoscale zero-valent iron functionalized Posidonia oceanica marine biomass for heavy metal removal from water

Because of the excellent reducing capacity of nanoscale zero-valent iron (NZVI), it can be used as alternative materials for the removal of a variety of reducible water contaminants including toxic metals. The current paper reports the research results obtained for self-prepared biosorbent, Posidonia oceanica biomass, activated in alkaline medium and functionalized with NZVI particles. The structural characteristics, surface morphology, and binding properties of the resulting nanobiosorbent are presented. Batch comparative adsorption trials including adsorption kinetics and isothermals onto raw Posidonia, Posidonia–OH and Posidonia–OH–NZVI were investigated on three heavy metal ions: Cd(II), Pb(II), and Cu(II). The nanobiosorbent showed better properties, such as high reactivity and high uptake rate through the sorption process. The toxic metal removal has been monitored in terms of pseudo-first- and pseudo-second-order kinetics, and both Langmuir- and Freundlich-type isotherm models have been used to describe the sorption mechanism. The experimental data of all studied systems showed that the uptake kinetics follow the pseudo-second-order kinetic model and the equilibrium uptake can adopt the Langmuir-type isotherm model which assumes a monolayer coverage as the adsorption saturates and no further adsorption occurs. The thermodynamic results confirm that all sorption processes were feasible, spontaneous and thermodynamically favorable. Zeta potential data displayed that Cd(II), Pb(II), and Cu(II) tend to be reduced after exposure on the Posidonia–OH–NZVI surface. Furthermore, sorption competitions of the metals from binary and ternary systems were carried out onto Posidonia–OH–NZVI in order to gain further insight into the sorption efficiency of this material. Therefore, as a result, the proposed new nanobiosorbent could offer potential benefits in remediation of heavy metal-contaminated water as a green and environmentally friendly bionanocomposite.