Synthesis and Properties of New Multilayer Chitosan@layered Double Hydroxide/Drug Loaded Phospholipid Bilayer Nanocomposite Bio-Hybrids.

A novel bio-hybrid drug delivery system was obtained involving a Mg/Al-NO3 layered double hydroxide (LDH) intercalated either with ibuprofenate anions (IBU) or a phospholipid bilayer (BL) containing a neutral drug, i.e., 17ß-estradiol, and then embedded in chitosan beads. The combination of these components in a hierarchical structure led to synergistic effects investigated through characterization of the intermediates and the final bio-composites by XRD, TG, SEM, and TEM. That allowed determining the presence and yield of IBU and of BL in the interlayer space of LDH, and of the encapsulated LDH in the beads, as well as the morphology of the latter. Peculiar attention has been paid to the intercalation process of the BL for which all available data substantiate the hypothesis of a first interaction at the defect of the LDH, as well as on the interaction mode of these components. 1H, 31P and 27Al MAS-NMR studies allowed establishing that the intercalated BL is not homogeneous and likely formed patches. Release kinetics were performed for sodium ibuprofenate as well as for the association of 17ß-estradiol within the negatively charged BL, each encapsulated in the LDH/chitosan hybrid materials. Such new bio-hybrids offer an interesting outlook into the pharmaceutical domain with the ability to be used as sustained release systems for a wide variety of anionic and, importantly, neutral drugs.

Original synthesis and spectroscopic study of thiophene triazine derivatives with enhanced luminescence properties.

A straightforward access to π-conjugated oligothiophenes bearing amino-rich groups was developed. Palladium-catalyzed C-H arylation applied in the main step of the synthesis allowed to couple 2-thiophenecarbonitriles and aryl bromides with moderate to excellent yields (35-93%). Then, to improve their basic fluorescence properties, these compounds were transformed into their 2,4-diamino-1,3,5-triazine derivatives, also with good to excellent yields (74-98%). UV-Visible absorption and fluorescence studies identified a strongly emissive molecule (fluorescence quantum yield: ΦF = 0.78 ±â€¯0.05), which could find use in sensors for applications in biology and in material chemistry. We observed an antagonistic effect in the spectroscopic properties of oligothiophenes bearing 2,4-diamino-1,3,5-triazine, resulting in improved absorptive and emissive properties for more constrained structures having shorter oligothiophenes chains.

Preparation of layered double hydroxide/chlorophyll a hybrid nano-antennae: a key step.

In the first step to obtain an efficient nano-antenna in a bottom-up approach, new hybrid materials were synthesized using a set of layered double hydroxides (LDHs) with basic properties and pure chlorophyll a (Chl a). The stability of the adsorbed monolayer of Chl a was shown to be dependent on the nature and the ratio of the different metal ions present in the LDHs tested. The hybrid materials turned out to be adequate for stabilizing Chl a on Mg/Al LDHs for more than a month under ambient conditions while a limited catalytic decomposition was observed for the Ni/Al LDHs leading to the formation of pheophytin. These changes were followed by namely XRD, DR-UV-vis and fluorescence spectroscopies of the hybrid antennae and of the solutions obtained from their lixiviation with acetone or diethylether. On Mg/Al hydrotalcites the stability of the adsorbed Chl a was equivalent for values of the metal atom ratio ranging from 2 to 4. The latter hybrids should constitute a good basis to form efficient nanoscale light harvesting units following intercalation of selected dyes. This work describes an efficient preparation of Chl a that allows scale-up as well as the obtention of a stable Chl a monolayer on the surface of various LDHs.

Azoic dye hosted in layered double hydroxide: physicochemical characterization of the intercalated materials.

Intercalation compounds were obtained by introduction of guest methyl orange (MO) into the interlayer space of host Mg/Al and Ni/Al layered double hydroxides (LDHs). Three synthesis methods of organic anion-LDH intercalation compounds, i.e., coprecipitation, reconstruction of the MII(Al)O mixed oxides, and anion exchange of LDH, were compared. The former method gives rise to a highly organized MO-intercalated Mg/Al LDH with an interlayer spacing of 2.43 nm and up to seven (00l) reflection orders. Reconstruction of the mixed oxide by intercalation with MO in the restored LDH was only achieved with Mg(Al)O. In this case, a competitive adsorption of MO on the external surface of the crystals was also seen. On the other hand, intercalation compounds exhibiting interlayer spacing of 2.43 nm were obtained with both Mg- and Ni-containing LDH using the anionic exchange method. The equilibrium and kinetic adsorption properties of the compounds were analyzed by UV-visible spectroscopy in anionic exchange experiments. According to the pseudo-second-order adsorption model, the amounts of adsorbed MO reach 3.82 and 2.83 mequiv/g for Mg- and Ni-containing LDHs, respectively, which are close to their respective anionic exchange capacity. The adsorption rates are on the same order of magnitude for the two LDHs (0.10-0.44 g mmol(-1) min(-1)), the equilibrium being reached in less than 60 min. The decomposition of MO by combustion of the organic moieties under an oxidizing atmosphere is delayed in Mg-containing MO-LDH hybrids when compared to the free MO molecule, showing that the thermal stability of MO species is enhanced after intercalation. In Ni-containing LDH, the main decomposition step of MO occurs 300 degrees C below that of Mg-containing LDH. This was rationalized in terms of a catalysis by the Ni-containing oxides formed during the thermal treatment. So these materials exhibit several advantages useful for the development of eco-friendly processes for the removal of dyes from effluents of textile, plastic, and paper industries.

Single-step dispersion of functionalities on a silica surface.

A new process for coating a mesoporous silica gel with a mixture of the grafting reagents para-aminophenyltrimethoxysilane and phenyltrimethoxysilane is thoroughly analyzed. The dilution of para-aminophenylsilane with phenylsilane at different ratios allows the density of the functional amino groups present on the silica surface to be controlled, while keeping constant the overall number of grafts. Furthermore, the choice of a rigid linker prevents undesirable interactions between the active function and the inorganic support that could alter the function reactivity. This simple and new method, which results in the improvement of the dispersion of a functionality in a one-pot synthesis, could be particularly interesting in the field of supported catalysis and molecular recognition. The dispersion of the functional groups of the synthesized hybrid solids is investigated using a pyrene derivative covalently linked to the free amino groups of the para-aminophenylsilanes by analyzing the excimer and monomer fluorescence properties of the probe.

Liposil, a promising composite material for drug storage and release.

Preliminary tests in the field of drug storage and release of composite materials known as liposils were described. These silica-based particles were obtained via liposome templating. The non-porous amorphous silica cladding of liposils protected the liposomes which retained the fundamental properties of their phospholipid bilayer. In an improved synthesis, two formulations were used, one with and the other without cholesterol in the phospholipid bilayer. Stability tests were done using carboxyfluorescein as a model hydrophilic drug loaded in the liposomes aqueous phase before the templating process. The stability of the loaded liposils was analyzed at two different pH (1.2 and 7.4) in a flow cell, according to the USP 28 norm. At pH 1.2, the silica shell was stable and prevented their rapid degradation. Interestingly, at pH 7.4 the analysis of the release kinetics revealed that the hydrolysis of the silica shell initially released intact liposomes. Characterizations of liposils were done at various steps of these processes. The stability observed for liposils make them good starting material for drug storage and release schemes. For instance, functionalization of their external surface should improve their capture by cells whereby drug release could then be induced by external stimuli, such as ultrasounds or microwaves.

Theoretical study of DHEA: comparative HF and DFT calculations of the electronic properties of a complex between DHEA and serotonin.

Molecular parameters (interatomic distances and angles, total atomic charge, dipole moments) of DHEA (Dehydroepiandrosterone), serotonin and of their putative complex including its heat of formation, have been computed in an ab initio comparative study involving HF and DFT calculations. The 6-31G* basis set and the B3LYP functional were employed. The aim of this study is to emphasize by DFT calculation the possible existence of a complex between DHEA and serotonin that may have the properties of a new drug. A Natural Bond Orbital analysis description offers supplementary details for the structure of the molecular units and their interaction.