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cited By 0; International audience; Chitosan (an amino‐polysaccharide obtained from deacetylation of chitin, the major constituent of crustaceous shells and insect cuticles) presents a cationic character in acidic media allowing its dissolution, its shaping and possible ion‐exchange interactions with anionic compounds (a property applied in adsorption and coagulation–flocculation processes). In neutral media, non‐protonated amino groups allow complexation of metal cations or organic chemicals. These different properties explain the interest taken by the scientific community in using this biopolymer. In solution it contributes to complex metals and their recovery by complexation‐assisted ultrafiltration. It can also be used to coagulate–flocculate organic compounds (as anionic dyes). In the solid state, it can be used for metal ion adsorption, as well as adsorption of organic compounds (dyes, pesticides, drugs, endocrine disruptors, etc.). The adsorption and coagulation–flocculation processes will be compared and examples considered. Moreover, it is noteworthy that the thermal degradation of this type of material is also more environmentally friendly than that of conventional synthetic resins (production of hazardous by‐products, etc.), a supplementary advantage of these biopolymer‐based sorbents. Combined with its ability to be chemically or physically modified improving the potential and phase separation of chitosan‐based materials, all these properties mean it is an excellent candidate for wastewater treatment.

cited By 0; International audience; In this paper, we study the possibility of valorization of the waste of crustaceans and cephalopods, rejected by the seafood restaurants in Essaouira, by the production of chitin and chitosan. It is part of the continuity of previous works which have been interested in the exploration of the chitinous sources of the Moroccan coast and in the preparation of chitins and chitosan with controlled physico-chemical characteristics. We realized an investigation about fishing activity in Essaouira and the quantities of waste from marine sources that could be valorized, Sources chosen further to this investigation were the object of reactions of extraction and of N-deacetylation to prepare the chitin and the chitosan. The followed processes are chosen to obtain products of good quality; in particular chitosan of varied molar weight but highly deacetylated (low degree of acetylation DA) were targetted. An estimation of the annual quantities of chitin and chitosan can be produced only from the waste of restaurants in this small coastal city will be presented.

International audience; In order to analyze the effect induced by encapsulating the drug in liposomes, comparative studies were performed for control hydrogels and complex systems (the same hydrogels containing liposomes). The results showed that the use of liposomes entrapped within chitosan hydrogels allows a strong decrease of burst effect and, moreover, the mechanism of drug release is a complex Fickian diffusion, consisting of drug diffusion through the swollen hydrogel and/or water filled pores, being continuously fed by calcein loaded in liposomes.

International audience; The production of cationized chitosan derivatives via reaction between chitosan and quaternary epoxides has the advantage of producing substances with a better regioselectivity and with structures that do not change as a function of pH, unlike N,N,N-trimethylchitosan. Moreover, this reaction allows the production of cationized derivatives having different hydrophobic/hydrophilic balances because quaternary epoxides with different alkyl chains can be used in this reaction. The effects of reaction parameters, namely time, temperature and glycidyltrimethylammonium chloride (GTMAC)/chitosan (Ch) molar ratio, on the structural and hydrodynamic characteristics of N-(2-hydroxy)propyl-3-trimethylammoniumchitosan chloride (ChCat) and on reaction yield were evaluated using chemometrics and response surface methodology (RSM). Structural characterization and determination of intrinsic viscosity were realized using spectroscopic techniques (Fourier transform infrared and 1H NMR) and capillary viscometry, respectively. The polynomial functions and RSM developed from 23 full-factorial analysis show the influence of the reaction parameters on the characteristics and properties of the ChCat produced, permitting the choice of appropriate reaction conditions to suit its desired application. Results show, as an example, that when the N-substitution is carried out for 6h at 50°C employing excess of GTMAC (GTMAC/Ch=4:1), water-soluble moderately substituted (DS = 33.0%) ChCat ([η]=293.4 mLg-1) can be produced with moderate reaction yield (30.9%). Furthermore, as GTMAC is the simplest quaternary epoxide, the study of its reaction with chitosan serves as a template for more complex quaternary epoxides as they may be used for the production of new cationized chitosan derivatives possessing alkyl chains with various chain lengths. © 2016 Society of Chemical Industry.

cited By 2; International audience; The synthesis of new derivatives of 1,3,4-thiadiazoles and 1,2,4-triazoles was achieved using the 1,4-disubstituted thiosemicarbazides as intermediaries. © 2013 HeteroCorporation.

cited By 5; International audience; New thiazolidine 2,3 disubstituted derivatives of 1'-acetamidyl-5'-nitroindazole with antitumoral activity against the Walker Carcinosarcoma and Jensen Sarcoma were designed and synthesized. The structural features of new compounds have been established by chemical elemental and spectral ( 1HNMR and IR) analyses. The optimized molecular geometry, the length of the covalent bonds, the atomic charges and some electro-optical parameters influencing the bioactivity of the new compounds were established by using HyperChem 5.0 programs. The determined values of the 1,3-thiazolidines toxicity are in the limits of the laboratory screening. The new compounds prove inhibition activity when they were tested on experimental tumors, the most active being 4-oxo-1,3-thiazolidine (VI) with ortho-hydroxy-phenyl.

cited By 4; International audience; New biologically active compounds, obtained by synthesizing new hydrazides derived from benzoxazolyl-2mercaptoformic acid, respectively benzoxazolyl-2-mercaptoacetic acid, have been chemically immobilized onto poly(maleic anhydride-alt-vinyl acetate) supports, forming drug-polymer conjugates with controlled delivery. The reaction products were characterized by elemental and spectral analyses (FT-IR, 1H-NMR). Toxicological and tuberculostatic activity tests recommend certain reaction products as therapeutic candidates with pharmacological application.

cited By 4; International audience; New 1,3,4-oxadiazoles with pharmacological potential, derived from 5-nitroindazole, have been synthesized. Their chemical structure has been established by elemental and spectral analyses (FT-IR and 1H-NMR). The oxadiazoles presented low toxicity, one compound, either in a free form or loaded in polymeric microcapsules, also showing a remarkable antipyretic activity, similar to that of acetylsalicylic acid.

International audience; abstract simple

cited By 4; International audience; The aim of this work is obtaining and characterizing Interpenetrating Network hydrogel based microparticles. They are elaborated by the inverse emulsion co-crosslinking reaction of carboxymethylcellulose and gelatin with epichlorohydrin. The influence of parameters related with the particles elaboration process (ratio of polymers in the mixture, ratio between polymer mixture and crosslinking agent, concentration of polymer solution, duration of crosslinking reaction, stirring intensity...) on their composition, size and swelling ability was studied. Obtained microparticles fulfill the requirements for biomaterials: to be formed from biocompatible polymers, the acute toxicity value (DL50) is high enough to consider these materials as weakly toxic (hence able to be introduced within the organism). They are able to include and release drugs in a controlled way and tests carried out with cefotaxime loaded microparticles demonstrate their antibacterial activity.

cited By 20; International audience; This paper provides the experimental results evidencing the potential of chitosan utilisation as a wet-end additive in papermaking. The research analyzes the colloidal behaviour of chitosan, investigated in terms of its interactions with the anionic polymers (carboxymethylcellulose - CMC, and anionic Polyacrylamide PAA), as well as with the colloidal and dissolved material (CDM) of papermaking process water. The shape of colloidal titration curves and particle size distribution of process water, measured by laser diffraction, have indicated that chitosan has a higher ability to form polyelectrolyte complexes (PEC), comparatively with other cationic additives frequently used in wet-end systems, such as PDADMAC and polyethylenimine (PEI). Lab tests simulating short circuit of paper machine have shown that chitosan and PDADMAC have similar effectiveness in reducing the accumulation rate of CDM, even if the effects on paper stock drainage and paper strength are much higher in the case of chitosan.

cited By 10; International audience; Polysaccharide-based hydrogels, such as xanthan maleate/poly(N-isopropylacrylamide) (PNIPAAm) interpenetrated polymer networks, are thermostimulable materials of interest for the controlled release of biologically active components due to conformation changes at the low critical-solution temperature (LCST) PNIPAAm phase transition. The phase transition of these interpenetrated polymer network hydrogels, where PNIPAAm is in a 'confined' environment, was examined by high resolution magic angle spinning nuclear magnetic resonance and differential scanning calorimetry. High resolution magic angle spinning nuclear magnetic resonance spectroscopy allows the accurate determination of LCST and an evaluation of the corresponding thermodynamic data. More particularly, the evolution of these data as a function of the composition of the hydrogel, and of the external parameters such as pH and ionic strength, was considered. LCST shows a minimal value with increasing xanthan content. Moreover, it was possible to calculate, as a function of temperature, the fraction of NIPAAm which remains uncollapsed. The data obtained for pure PNIPAAm hydrogels are in good agreement with recently published results. The phase transition of PNIPAAm in a diphasic hydrogel is broader when PNIPAAm is 'confined' within an interpenetrated polymer network than in a pure PNIPAAm crosslinked network. The widening of the transition with increasing xanthan content indicates a reduction of the PNIPAAm interchain aggregation in a network structure. © 2011 Society of Chemical Industry.

cited By 0; International audience; no abstract

International audience

cited By 16; International audience; Complexes obtained from the electrostatic interactions between chitosan, a cationic polysaccharide, and sodium decylsulfonate, an anionic surfactant, were characterized by their conductimetric and surface-active properties. Such surfactant/polyelectrolyte complexes (SPECs) present very interesting surface-active properties, even at very low surfactant concentrations (much lower than the critical micellar concentration, CMC, of pure surfactant), influencing either surface tension or viscoelastic properties of the adsorbed layers. This allows their use as emulsion stabilizers, while the very low surfactant concentration makes them potential candidates for cosmetic applications.

International audience; abstract simple

International audience; This article reports the synthesis and characterization of a new polythiophene derivative phenoxy-substituted, the poly[3-(4-octylphenoxy) thiophene] (POPOT). The oxidative polymerization was found to yield low molecular weight material, whereas a modified Grignard metathesis (GRIM) yielded polymers of high molecular weights. One- and two-dimensional NMR indicated the latter to be highly regioregular. POPOTs exhibited higher thermal stabilities than equivalent alkoxy-substituted polythiophenes and exhibited red shifts in the absorption spectra with respect to equivalent. The absorption spectra showed a red shifted λmax at 540 nm in tetrahydrofuran solutions and 580 nm in spin-coated films, with respect to poly(3-alkylthiophene)s. A further red shift of 40 nm in going from solution (540 nm) to solid states (580 nm) is correlated with results from density functional theory electronic structure calculations. © 2008 Wiley Periodicals, Inc.