Fatty acid intercalated layered double hydroxides were used as additives for Jojoba oil and polymer matrices. The first phase of the study was to intercalate carboxylic acids (C14 to C22). These were successfully intercalated into layered double hydroxides (LDHs), with the formula [Mg0.7Al0.3 (OH) 2](CO3)0. 15•0.5H2O. The one-pot synthesis consistently yielded a bilayer intercalated product for the range of acids employed. The intercalated anions had an orientation tilt angle of 55–63°, depending on the length of the fatty acid chain. However, there is an indication that the anion exchange process employed in this study is accompanied by probable dissolution and recrystallisation of the LDH. This is supported by the different growth habits and sizes of platelets observed through scanning electron microscopy (SEM). Moreover, the organo-LDH platelets were found to have varying MII/MIII compositions, ranging from 1.65 to 6, indicating that the one-pot synthesis yields an array of mixed metal hydroxides. Polymer composites, containing 5% and 10 wt.% of stearate intercalated layered double hydroxides (LDH-stearate) and neat layered double hydroxides (LDH-CO3), were prepared via melt-compounding to explore the use of LDHs as an additive. The stearate modified starting material was bilayer-intercalated clay. During melt compounding, excess stearates were released and the clay reverted to a monolayer-intercalated form. Comprehensive characterisation and study of the fatty acid-intercalated LDH showed that these organoclay hybrids exhibit thermotropic behaviour. This behaviour ultimately leads to the exudation of excess fatty acid. The exuded stearates were found to have lubricating and plasticising effects on the poly(ethylene-co-vinyl acetate) (EVA) and linear low density polyethylene (LLDPE) matrices. Strong hydrogen bond interactions between the chains of poly(ethyleneco- vinyl alcohol) (EVAL) and the clay platelet surfaces overwhelmed the lubrication effect and caused an increase in the melt viscosity of this matrix. The notched Charpy impact strength of this composite was almost double that of the neat polymer. It appears that this can be attributed to the ability of the highly dispersed and randomly oriented nanosized clay platelets to promote extensive internal microcavitation during impact loading. The creation of a large internal surface area provided the requisite energy dissipation mechanism. The study also considered fatty acid-intercalated LDH as an argillaceous mineral for potential use as a rheological additive in Jojoba oil. A minimum of 20 wt.% LDH in Jojoba oil formulation was found to be stable, i.e. it did not form separate layers on standing. The viscosity of the neat Jojoba oil demonstrated Newtonian behaviour, whereas the modified LDH/Jojoba oil formulation shear thinned, which is a typical non-Newtonian behaviour. Viscosity as a function of temperature showed complex rheological behaviour for the long chain fatty acids C16 to C22. The viscosity increase is assumed to be due to a combination of three events, which include the formation and changes of LDH microstructures within the oil, the loss of excess fatty acids into the oil matrix, and the formation of fatty acid crystal networks. Shear action also induced some delamination of the clay platelets. / Thesis (PhD(Eng))--University of Pretoria, 2012. / Chemical Engineering / unrestricted

Surfactant-mediated intercalation of aliphatic fatty acids into a commercial,layered double hydroxide (LDH) with the approximate composition of [Mg0.689Al0.311(OH2)] (CO3)0.1569nH2O was explored. The reactions were conducted at elevated temperatures with the LDH powder suspended in a fatty acid oil-water emulsion. The acidic fatty acid, e.g. stearic acid, reacts with the basic carbonate anions from LDH-CO3. In the process, CO2 is released as a gas and the fatty acids are intercalated as a bilayer. A high concentration of anionic or non-ionic surfactants, i.e. sodium dodecylsulphate or Tween 60, facilitates the intercalation process by emulsifying the molten fatty acids and dispersing the LDH particles. The presence of carboxylate anions in the interlayer region was confirmed by the carboxylate absorption peaks observed in the region 1700–1000 cm-1 on Fouriertransform infrared spectroscopy (FT-IR). Several bands were observed, i.e. ionised and non-ionised. An increase in the d-spacing of the d003 plane of the brucite-like LDH layers was observed on X-ray diffraction (XRD) analysis of all the LDH intercalates. The d-spacing increased linearly with the length of the carboxylic acid chain. Sharp reflection peaks were obtained on XRD, showing the high crystallinity of the LDH intercalates. The thermal decomposition of these materials was explored on thermogravimetric or differential thermogravimetric analysis (TGA/DTA) and temperature-scanned XRD. The mole ratio of Mg to Al was obtained by XRF and the morphology by scanning electron microscopy (SEM). The present method works well with long-chain aliphatic fatty acids at temperatures above or at the melting point of the desired acid. Temperature proved to be the most important parameter to control during the preparation process, i.e. at low temperatures incomplete reactions were obtained. The method is convenient, economical and environmentally friendly. It employs the readily available carbonate form of LDH as a starting reagent, water is used as medium rather than organic solvents, there are no high-temperature calcinations, and an inert atmosphere is not required. Copyright / Dissertation (MSc)--University of Pretoria, 2008. / Chemistry / unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19740号 / 工博第4195号 / 新制||工||1647(附属図書館) / 32776 / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 阿部 竜, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

There has been much interest in the use of therapeutics based on ribonucleic acid interference(RNAi) to inhibit synthesis of mutant proteins ever since Elbashir et al. (Elbashir, S. M., Harborth, J., Lendeckel, W., Yalcin, A., Weber, K. and Tuschl, T., 2001. Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells. Nature. 411, 494-498.) found that synthetic double stranded small interfering ribonucleic acids (siRNAs) can initiate this evolutionarily conserved process in mammalian cells. Since RNAi is able to target single genes and therefore mitigate the underlying molecular pathology of diseases, RNAi-based therapeutics will most likely benefit monogenic neurodegenerative diseases such as Huntington’s disease. It is however particularly difficult to deliver exogenous materials such as siRNAs into neurons in vivo as the blood-brain barrier (BBB) isolates the brain from the vascular system and prevents permeation of most materials. Neurons also do not take up exogenous materials readily. Therefore, effective delivery of siRNAs into the brain remains one of the biggest challenges impeding their use as a potential neurotherapeutic. Layered double hydroxide (LDH) nanoparticles are a class of anionic clay materials that have demonstrated great potential as a DNA (deoxyribonucleic acid) delivery system for a variety of mammalian cell lines due to their unique physiochemical properties. This thesis examined the feasibility of LDH as a siRNA delivery system for cultured neurons and demonstrated that the delivered siRNAs are able to effectively down-regulate synthesis of a target protein with minimal toxicity. Experiments were conducted using double stranded DNAs (dsDNAs) initially, and siRNAs were then used to verify these results. It was shown that nucleic acids(dsDNAs and siRNAs) could successfully intercalate into pristine LDHs to form nucleic acid-LDH complexes that had properties suitable for use as a delivery system in mammalian cells. These studies established that LDHs and nucleic acid-LDH complexes were biocompatible with neurons isolated from embryonic day 17.5 mouse cerebral cortex, suggesting that LDH can be used for nucleic acid delivery into cultured neurons. LDHs were also shown to successfully deliver nucleic acids into a non-neural mammalian cell line (NIH 3T3 cells). Finally, this thesis demonstrated for the first time that LDHs were able to deliver siRNAs into neurons, providing encouraging preliminary evidence that sequence specific gene silencing of the Mus Musculus Deleted in Colorectal Cancer (DCC) gene had occurred. However, down-regulation of the DCC protein did not occur consistently, suggesting that further optimisation is needed to improve the efficacy of siRNA-LDH complexes to inhibit expression of target protein in neurons. In future, LDHs should be further developed as an efficient siRNA delivery system for therapeutic gene silencing in the central nervous system using a neurodegenerative disease model such as the Huntington’s disease mouse model, which closely phenocopies the human disease. This model will allow the in vivo efficacy of these nanoparticles to be tested and subsequently improved in order to deliver siRNAs locally and systematically into the brain.

There has been much interest in the use of therapeutics based on ribonucleic acid interference(RNAi) to inhibit synthesis of mutant proteins ever since Elbashir et al. (Elbashir, S. M., Harborth, J., Lendeckel, W., Yalcin, A., Weber, K. and Tuschl, T., 2001. Duplexes of 21-nucleotide RNAs mediate RNA interference in cultured mammalian cells. Nature. 411, 494-498.) found that synthetic double stranded small interfering ribonucleic acids (siRNAs) can initiate this evolutionarily conserved process in mammalian cells. Since RNAi is able to target single genes and therefore mitigate the underlying molecular pathology of diseases, RNAi-based therapeutics will most likely benefit monogenic neurodegenerative diseases such as Huntington’s disease. It is however particularly difficult to deliver exogenous materials such as siRNAs into neurons in vivo as the blood-brain barrier (BBB) isolates the brain from the vascular system and prevents permeation of most materials. Neurons also do not take up exogenous materials readily. Therefore, effective delivery of siRNAs into the brain remains one of the biggest challenges impeding their use as a potential neurotherapeutic. Layered double hydroxide (LDH) nanoparticles are a class of anionic clay materials that have demonstrated great potential as a DNA (deoxyribonucleic acid) delivery system for a variety of mammalian cell lines due to their unique physiochemical properties. This thesis examined the feasibility of LDH as a siRNA delivery system for cultured neurons and demonstrated that the delivered siRNAs are able to effectively down-regulate synthesis of a target protein with minimal toxicity. Experiments were conducted using double stranded DNAs (dsDNAs) initially, and siRNAs were then used to verify these results. It was shown that nucleic acids(dsDNAs and siRNAs) could successfully intercalate into pristine LDHs to form nucleic acid-LDH complexes that had properties suitable for use as a delivery system in mammalian cells. These studies established that LDHs and nucleic acid-LDH complexes were biocompatible with neurons isolated from embryonic day 17.5 mouse cerebral cortex, suggesting that LDH can be used for nucleic acid delivery into cultured neurons. LDHs were also shown to successfully deliver nucleic acids into a non-neural mammalian cell line (NIH 3T3 cells). Finally, this thesis demonstrated for the first time that LDHs were able to deliver siRNAs into neurons, providing encouraging preliminary evidence that sequence specific gene silencing of the Mus Musculus Deleted in Colorectal Cancer (DCC) gene had occurred. However, down-regulation of the DCC protein did not occur consistently, suggesting that further optimisation is needed to improve the efficacy of siRNA-LDH complexes to inhibit expression of target protein in neurons. In future, LDHs should be further developed as an efficient siRNA delivery system for therapeutic gene silencing in the central nervous system using a neurodegenerative disease model such as the Huntington’s disease mouse model, which closely phenocopies the human disease. This model will allow the in vivo efficacy of these nanoparticles to be tested and subsequently improved in order to deliver siRNAs locally and systematically into the brain.

The intercalation of surfactant anions, namely sodium dodecyl sulphate, sodium benzene sulphonate and lauric acid, into commercial layered double hydroxides (LDH-CO3) with approximate composition [Mg0.654AI0.346 (OH)2](CO3)0.173.0.5H2O] was explored. LDH-CO3 is commercially available in bulk form owing to its large scale applications as a PVC stabiliser and acid scavenger in polyolefins. It is therefore of interest to investigate intercalation methods using LDH-CO3 as starting material. The intercalation method used was compared with the pre existing procedures, for instance the co-precipitation, ion exchange and regeneration methods. Due to the tenacity with which the carbonate ion is held in LDH-CO3, direct ion exchange is an intricate matter. Hence, in the regeneration method the carbonate ion is removed by thermal treatment and the LDH-surfactant is obtained by reaction of the LDH and surfactant in an aqueous medium. Nevertheless, the resulting products are impure and poorly crystallised, and only partial intercalation is achieved. The underlying principle of the current method is protonation of the carbonate anion to a monovalent anion that is easily exchanged with surfactant anions. Improved results were obtained when water-soluble organic acids were used, the most suitable being lower aliphatic carboxylic acids, e.g. acetic, butyric and hexanoic acid. In contrast, higher linear aliphatic carboxylic acids are preferentially intercalated to the anionic surfactants. In both cases the carboxylic acids are assumed to assist intercalation by facilitating the elimination of the carbonate ions present in the anionic clay galleries. X-ray diffraction analysis, thermal analysis and infrared spectroscopy confirmed the monolayer intercalation of LDH-dodecyl sulphate and LDH-dodecylbenzene sulphonate. In contrast, LDH-laurate featured a bilayer structure. / Dissertation (MSc)--University of Pretoria, 2009. / Chemistry / unrestricted

Bilayers formed by molecules that possess long alkyl hydrophobic tails are ubiquitous in the natural world manifesting both in biological systems as well as in chemistry. The lipid bilayer is an integral feature of cell membranes of living systems with functions that are of critical importance to the life of the cell. Long chain amphiphilic surfactant molecules can be introduced within the interlamellar region of layered inorganic host lattices to form anchored alkyl chainbilayerswithinthegalleries.Theintercalatedbilayerbearsastriking resemblance to lipid bilayers. However, unlike lipid bilayers where individual molecules can undergo lateral diffusion and also flip-flop between layers the anchored bilayer is characterized by the total absence of translational mobility. The degrees of freedom of the alkyl chains of the anchored bilayer are restricted to changes in conformation. This thesis describes a detailed investigation of the anchored bilayer formed by the intercalation of the anionic surfactant dodecyl sulphate (DDS) in a layered solid, Mg-Al Layered Double Hydroxide(Mg-AlLDH) using both experimental measurements and Molecular Dynamics (MD) simulations (Chapter 2). The thesis is organized as two parts. The first (Chapters 2 -4) deals with the anchored bilayer in the condensed phase -the conditions for the formation of the bilayer arrangement of the intercalated surfactant chains and the conformation and dynamics of the alkyl chains of the surfactant in the galleries of the layered solid. The surfactant intercalated Mg-AlLDH-DDS may be delaminated in nonpolar solvents to give colloidal dispersions of individual Mg-Al LDH sheets with the DDS surfactant chains remaining tethered to the inorganic sheets(Scheme 1).The second part of thesis(Chapters 5 -9)describe studies on the dispersions of the Mg-AlLDH-DDS in toluene. A summary of the results of the of the investigations of the anchored bilayer, formed by the intercalation of DDS ions in Mg-Al LDH, in the condensed and the dispersed phases is presented in the concluding chapter(Chapter10). Layered Double Hydroxides(LDH) are insulating lamellar solids of the general chemical formula[M’(1-x) Mx(OH)2], where M’ is a divalent metal ion and M a trivalent ion. Their structure may be derived from that of Brucite, Mg(OH)2, by isomorphous substitution of apart of the Mg2+ by trivalent ions like Al3+ with electrical neutrality maintained by interlamellar exchangeable ions. The studies reported in this thesis are on an Mg-Al LDH,Mg(1−x)Alx(OH)2, x ranging from 0.17 to 0.37. Dodecyl sulphate surfactant ions have been ion-exchange intercalated in Mg-AlLDH (Chapter 3). By varying the Mg-Al ratio, differing packing densities of the surfactant chains in the interlamellar space of the Mg-Al LDH-DDS are realized. At high packing densities the alkyl chains of the intercalated dodecyl sulphate ions anchored on opposing Mg-Al LDH sheets are arranged as bilayers while at lower packing densities the surfactant chains form a monolayer with the chains oriented flat in the galleries. This composition driven monolayer to bilayer transformation in the surfactant intercalated Mg-AlLDH-DDS is also reproduced by MD simulations. The simulations also indicate that there are profound differences in the factors that decide the arrangement of the surfactant chains. In the bilayer arrangement it is dispersive van der Waals interactions between the chains in opposing layers that is responsible for the cohesive energy of the solid whereas at lower packing densities, where a monolayer arrangement is favored, Coulomb interactions between the positively charged Mg-Al LDH sheets and the negatively charged head-group of the DDS anion dominate. The conformation and dynamics of the alkyl chains of the intercalated surfactant chains in both the monolayer and bilayer arrangements as well as the effect of packing density on these parameters is reported in Chapter 4. The conformation was studied using spectroscopic techniques, infra-red, Raman and 13C Nuclear Magnetic Resonance (NMR) while the dynamics by Variable Contact Time Cross Polarization Magic Angle Spinning(VCT -CPMAS) and2DWidelineSeparation(2DWiSe)NMR techniques. The results showed the expected trends; the concentration of gauche defects and the dynamics of the chains increase with decreasing packing density. There is, however a sharp increase in the gauche concentration and conformational mobilities of the intercalated surfactant chains associated with the bilayer to monolayer transformation. The results of the MD simulations, too, reflect these trends. The second part of thesis describes the delamination of the intercalated anchored bilayer (Mg-AlLDH-DDS) in non-polar solvents. Delamination results in a colloidal dispersion Of the anchored bilayer, isolated Mg-AlLDH sheets with the DDS chains tethered to them, as neutral nanosheets of nanometer thickness and micron size. With increasing concentration of the anchored bilayers in the solvent a gel state is realized. The sol to gel transformation of the dispersions of the anchored bilayer in toluene has been investi-gated. Frequency dependent rheology measurements (Chapter6) were used to investigate the visco-elastic properties of the dispersions and Small Angle X-ray Scattering (SAXS) measurements(Chapter 7) to understand the structure and shape of the nanosheets. The rheology experiments showed that the dispersions irrespective of their concentrations showed shear thinning. The SAXS results indicate a tactoid structure of the dispersions as well as in the gel phase. At higher concentrations, the X-ray scattering curves indicated that the layers stack loosely with an interlamellar space of ~ 39 Å , a value much larger than the interlayer lattice spacing of solid Mg-AlLDH-DDS( ~ 27 Å). The nature of interactions between solvent molecules and the anchored DDS chains were probed by 1Hand 2H NMR measurements(Chapter8). A clear association between the toluene molecules and the alkyl chains of the anchored surfactant was observed. 2D NOESY experiments established that there are toluene molecules in close proximity that interact with the methyl tail of the anchored surfactant. NMR measurements were also able to distinguish two types of solvent molecules based on their widely differing mobilities. MD simulations(Chapter9)of the dispersed anchored bilayer are able to reproduce the essential features of the experimental observations including the formation of a loosely bound lamellar structure. It also provides an explanation on how the spectroscopic observation of motional heterogeneity gives rise to the viscoelastic properties of the dispersed anchored bilayer.

L’alliage d’aluminium 2024 est très répandu dans l’industrie aéronautique et automobile. Le processus de corrosion peut entrainer des dommages irréversibles pouvant engendrer des issues fatales dans le domaine aéronautique. Ainsi plusieurs couches de revêtements sont déposées à la surface du métal à protéger pour prévenir le processus de corrosion. Depuis le début du 20ième siècle, le chrome hexavalent (CrVI) a été largement utilisé comme inhibiteur de corrosion dans les différentes couches du revêtement (prétraitement, primer et top-coat). La toxicité de ce composé envers l’homme et l’environnement a entrainé son interdiction et donc son remplacement comme agent de protection. Le confinement d’agent anticorrosif dans des nano-conteneurs a ainsi été reporté puisqu’un effet auto-réparant, en relargant sur demande, peut-être apporté : l’inhibiteur de corrosion agit quand le dommage apparait. Cette étude est focalisée sur l’utilisation de matériaux de type Hydroxydes Doubles Lamellaires (HDL) comme réservoir d’inhibiteurs de corrosion en raison leur propriété d’échange. Dans ce travail, plusieurs molécules ont été étudiées comme potentiel inhibiteur de corrosion. Celles-ci ont été tout d’abord caractérisées par DC-polarisation afin de déterminer la nature de leur comportement inhibiteur (anodique, cathodique ou les deux). Ensuite, ces agents anticorrosifs ont été intercalés dans des matrices HDL et leur capacité de relargage ainsi que leur comportement face au processus de corrosion ont été étudiés. Les particules HDL ainsi obtenues ont été dispersées dans la formulation d’un revêtement primaire et déposé directement sur l’alliage aluminium 2024. La résistance à la corrosion a été suivie par spectroscopie d’impédance complexe. Les propriétés d’auto-protection de notre revêtement (relargage d’agent anticorrosive encas de dommage) et leur propriété barrière, apportée par la morphologie lamellaire des nano-conteneurs, entrainant une diminution de la perméabilité aux espèces agressives (ex. eau, O2, électrolyte) responsable de l’apparition de cloques sur les revêtements, ont ainsi été caractérisées. / Aluminum alloy 2024 is widely used in aircraft and automotive industry. Corrosion processes can provide irreversible damage on the metal substrate which could have a tragic issue in the aircraft domain. Thus, several coating layers have been applied on the metal substrate to prevent corrosion process. Since the beginning of the 20th century, hexavalent chromate compounds have been extensively used as corrosion inhibitor agents for paint, primer and conversion coating. The toxicity for human health and environment has led to replace such compounds. The literature has reported different possibilities to replace such unfriendly compounds. Moreover, the entrapment of corrosion inhibitors in nanocontainer provides a self-healing effect by releasing, on demand, the active species when damage occurs. This study focuses on Layered Double Hydroxide (LDH) material as reservoir due to its exchange properties. This study has characterized several potential corrosion inhibitor molecules by DC-Polarization to determine the nature of the inhibitor compound (i.e. anodic, cathodic or both of them). Further, active anticorrosive species have been intercalated into LDH framework. Then, the release of inhibitor agents and their subsequent behaviour toward corrosion inhibition have been evaluated. Modified LDH materials have been further dispersed in the primer coating formulation and applied on aluminum alloys 2024 substrate. Corrosion inhibition has been followed by electrochemical impedance spectroscopy experiments on scratched and unscratched panel which have permitted to evaluate the self-healing property of these modified LDH materials when damage occurs and the barrier property provided by the lamellar morphology of the inorganic reservoir that is found to decrease the permeation by enhancing the tortuosity of the coating layer towards aggressive species (i.e. water, O2, electrolyte) responsible of the blistering phenomenon.

Les polyphénols sont des bioproduits générés par le métabolisme des végétaux. Récemment, ils ont attiré l’attention par leur impact potentiellement positif sur la santé, en grande partie lié à leur capacité antioxydante. Ils interviennent également dans les arômes de vin, café, thé… et intéressent donc l’industrie agroalimentaire. Le développement de biocapteurs adaptés à ces molécules est donc nécessaire, tout en respectant certains critères (simplicité d’utilisation, rapidité de la mesure, faible coût). Dans le cas des biocapteurs enzymatiques, l’étape déterminante est l'immobilisation de l’enzyme sur la surface du transducteur sans affecter ses performances.Dans cette thèse nous avons utilisé des matériaux de type « hydroxyde double lamellaires » (HDLs) comme matrice d’immobilisation de la tyrosinase, enzyme reconnaissant spécifiquement les polyphénols, afin de fonctionnaliser la surface d’électrodes d’or sérigraphiées. L’objectif était d’élaborer des microbiocapteurs pour détecter les polyphénols extraits du thé vert.Les HDLs ont été synthétisés par la méthode de coprécipitation directe, puis caractérisés par différentes méthodes physiques (spectroscopies Raman et infrarouge, diffraction des RX) afin de confirmer leur composition et de définir leur structure cristalline. Puis, des films minces bidimensionnels de HDL de différentes compositions ont été réalisés en faisant varier différents paramètres comme la nature du substrat, la concentration de la solution initiale de HDL et la méthode de dépôt (auto-assemblage « SAM » ou spin coating). L’étude morphologique de ces films a été réalisée par microscopie de force atomique (AFM) afin d’optimiser l’état de surface avant l’immobilisation de la tyrosinase. Le greffage de cette dernière a également été étudié par AFM. Enfin, une étude électrochimique (par voltammétrie cyclique et chronoampérométrie) nous a permis de déterminer les caractéristiques analytiques des microbiocapteurs ampérométriques ainsi élaborés. Les résultats ont montré que nos systèmes présentent une grande sensibilité aux polyphénols et sont capables de détecter ces molécules grâce à leur oxydation et aussi à la réduction des composés enzymatiquement générés par la réaction catalytique. Ils sont dynamiques dans une large gamme linéaire de détection (jusqu'à 1000 ng.mL-1) et peuvent également détecter des traces de polyphénols (de m’ordre de quelques pg.mL-1). / Polyphenols are in abundance in diet, being present in various fruits or vegetables, but also in tea or wine. Their antioxidant properties attracted an increasing interest of different researchers in the field of medicine and food manufacturers. Consequently, very intensive studies have been conducted to develop efficient polyphenols biosensors, while respecting certain criteria (simplicity of use, speed of measurement, low cost). In the case of enzymatic biosensors, the decisive step is the immobilization of the enzyme on the transducer surface without affecting its performances.In this thesis, we used layered double hydroxides (LDHs) as a host matrix to immobilize tyrosinase, an enzyme recognizing specifically polyphenols, at the surface of screen printed gold electrodes. Polyphenols used to study the biosensors were extracted from green tea.LDHs nanosheets were prepared by the co-precipitation method. In a first step, their structural properties were characterized by X-ray powder diffraction, Raman and Infra-Red spectroscopies, confirming crystalline phase and chemical composition of LDHs. In a second step, LDHs-thin films were prepared by self-assembly and spin coating deposition under various experimental conditions (nature and concentration of LDHs …), and studied by Atomic Force Microscopy (AFM) to obtain information about the surface morphology of the host matrix before enzyme immobilization. The presence of tyrosinase after the immobilization step was also confirmed by AFM. Electrochemical characteristics of the amperometric biosensors, whose design is based on this study, were determined by cyclic voltammetry and chronoamperometry. This study showed that these systems are highly sensitive to polyphenols, detecting them by their oxidation but also by the reduction of compounds enzymatically generated. They exhibit also other very attractive characteristics for the detection of complex mixture of polyphenols: a large dynamic range (up to 1000 ng.mL-1)and a very low detection limit (few pg.mL-1).