Layered double hydroxides-indomethacin nanohybrids: intercalation, pH influence, stability and release properties

In this work, three pH values (8, 9 and 10) were studied for the insertion of Indomethacin (Indo) molecules into Layered Double Hydroxides (LDHs). The obtained results showed that the LDH materials have been a good storage for the drug. LDHs provide thermal stability with an increase in the thermal decomposition of the drug around 100°C more. Indo into LDHs exhibited higher photostability to UV light irradiation. In vitro drug release experiments in a phosphate buffer solution (pH = 7.4) have been carried out. The loading amount of intercalated Indo was increased to 66 % at pH 8, and showed a profile of sustained release of 97 % in 8h. The release profiles were fitted by mathematical models, which describe various kinetic models that served to investigate the drug release mechanism, being the Bhaskar kinetics model the most appropriate. The results showed that the nanohybrids can be used as an effective drug delivery system.Fil: Mendieta, Silvia Nazaret. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Oliva, Marcos Iván. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; ArgentinaFil: Perez, Celso Francisco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; ArgentinaFil: Reyes Nuñez, Patricio. Universidad de Concepción; ChileFil: Longhi, Marcela Raquel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Investigación y Desarrollo en Tecnología Farmacéutica. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Unidad de Investigación y Desarrollo en Tecnología Farmacéutica; ArgentinaFil: Granero, Gladys Ester. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Unidad de Investigación y Desarrollo en Tecnología Farmacéutica. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Unidad de Investigación y Desarrollo en Tecnología Farmacéutica; ArgentinaFil: Crivello, Mónica Elsie. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigación y Tecnología Química. Universidad Tecnológica Nacional. Facultad Regional Córdoba. Centro de Investigación y Tecnología Química; Argentin

Growth Mechanism Of Titanium Nitride Nanowires And Their Physical, Structural And Biological Properties

In this work, titanium nitride nanowires have been grown on a magnesium oxide substrate using a pulsed laser deposition technique. The selection of titanium nitride as a material of interest has been made due to its stellar properties of high melting point, good diffusion barrier, high hardness, good electrical conductivity, and scattered reports in the literature about its biocompatibility. In this work, gold has been used as a catalys

Layered double hydroxides for corrosion-related applications: main developments from 20 years of research at CICECO

This work describes the main advances carried out in the field of corrosion protection using layered double hydroxides (LDH), both as additive/pigmentbased systems in organic coatings and as conversion films/pre-treatments. In the context of the research topic “Celebrating 20 years of CICECO”, the main works reported herein are based on SECOP’s group (CICECO) main advances over the years. More specifically, this review describes structure and properties of LDH, delving into the corrosion field with description of pioneering works, use of LDH as additives to organic coatings, conversion layers, application in reinforced concrete and corrosion detection, and environmental impact of these materials. Moreover, the use of computational tools for the design of LDH materials and understanding of ion-exchange reactions is also presented. The review ends with a critical analysis of the field and future perspectives on the use of LDH for corrosion protection. From the work carried out LDH seem very tenable, versatile, and advantageous for corrosion protection applications, although several obstacles will have to be overcome before their use become commonplace.publishe

Hidróxidos Duplos Lamelares (HDL) como nanoreservatórios versáteis para aplicação em revestimentos multifuncionais

The objective of the present work is synthesis and characterization of inorganic nanoreservoirs based on layered double hydroxides (LDH) loaded with active species, namely corrosion inhibitors and pH indicators. The most attractive feature of LDH is the anion-exchange ability. Despite the countless studies that describe the use of LDH for applications in protective coatings for anti-corrosion applications, the study related to immobilization and consequent release of anionic species is somewhat limited. Besides, there is still a lack of systematic studies correlating the structure of nanocontainers with properties (release profiles, triggering conditions) and the corresponding effect in coatings. In this work, several methodologies were used for preparation of LDH. Structure, morphology, colloidal and textural properties of resulting nanocontainers have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), dynamic light scattering (DLS), thermogravimetric analysis (TG) and nitrogen adsorption-desorption isotherms. Particular attention has been paid to the release studies of active species immobilized in LDH, determination of triggering conditions, establishment of kinetic models and definition of release mechanisms by UV-Visible spectrophotometry. Additionally, the adsorption of active species in LDH was investigated to understand how the active species are immobilized during the synthesis, as well as for evaluation of its impact on the application of nanoreservoirs in multi-functional coatings. In general, the release of active species is rate-limited by diffusion with possibility of anion-exchange reaction when anionic species are presenting in the environment. However, the release profiles, extent of release and adsorption of active species are strongly dependent on the method of synthesis and on the structure and properties of the active species. In addition, the LDH compositions studied were found to release the active species in response to the presence of anions in solution (e.g. chlorides, hydroxides, carbonates), even when the active species are not intercalated into the LDH galleries, but adsorbed onto the external surface of the particles. Besides, the propensity of LDH to dissolution or reaction under extreme pH conditions, in combination with changes in the surface properties, can play a role in the agglomeration and/or aggregation of the particles, thereby affecting adsorption and release of different species. Taking into account the properties of the materials obtained, it is possible to conclude that several LDH compositions studied in this work are prospecting additives for application in multi-functional coatings. Moreover, the present work can be used as some sort of library of experimental data to support the building and validation of computational models, to aid on the prediction of the uptake and release of active species from LDH.O objetivo do presente trabalho consistiu na síntese e caracterização de nanoreservatórios inorgânicos baseados em hidróxidos duplos lamelares (HDL) com diferentes espécies ativas imobilizadas, nomeadamente inibidores de corrosão e indicadores de pH. Uma das características mais relevantes associada com o HDL é a sua capacidade de permuta aniónica. Apesar dos inúmeros trabalhos que descrevem a utilização do HDL para aplicações em revestimentos protetores contra a corrosão, o estudo relacionado com a imobilização e consequente libertação das espécies aniónicas é algo limitado. Além disso, não existem estudos sistemáticos na literatura que correlacionem a estrutura dos nanocontentores com as propriedades (perfis e condições de libertação controlada) e o efeito correspondente nos revestimentos. Neste trabalho, várias metodologias foram aplicadas para a preparação dos HDL. A estrutura, morfologia, propriedades coloidais e texturais dos nanocontentores resultantes foram caracterizadas por difração de raios-X (DRX), espectroscopia no infravermelho por transformada de Fourier (FTIR), microscopia eletrónica de varrimento (SEM), dispersão dinâmica de luz (DLS), análise termogravimétrica (TG) e isotérmicas de adsorção-desadsorção de azoto. Atenção especial foi prestada aos estudos de libertação de diferentes espécies ativas imobilizadas em HDL, nomeadamente as condições experimentais que podem levar à libertação das espécies ativas (ex.: pH, presença de sais), estabelecimento de modelos cinéticos e definição de mecanismos de libertação, recorrendo à espetrofotometria de UV-Visível. Além disso, o processo de adsorção de espécies ativas foi investigado para tentar perceber o que ocorre durante a síntese de diferentes composições de HDL bem como avaliar o impacto na aplicação prática de nanoreservatórios em revestimentos multifuncionais. Os resultados obtidos permitem concluir que, de forma geral, a libertação de espécies ativas é determinada pela difusão, com possibilidade de reação de permuta aniónica, quando espécies aniónicas estão presentes no ambiente. No entanto, os perfis de libertação, extensão da mesma e adsorção de espécies ativas em HDL dependem do método de síntese, bem como da estrutura e propriedades das espécies ativas. Igualmente relevante, é que as diferentes composições de HDL apresentam capacidade de libertar as espécies ativas imobilizadas em resposta à presença de aniões na solução (ex.: cloretos, hidróxidos, carbonatos), mesmo quando não intercaladas nas galerias do HDL, encontrando-se apenas adsorvidas na superfície externa do HDL. Além disso, a tendência dos materiais de HDL à dissolução ou reação sob condições extremas de pH, em combinação com alterações nas propriedades da superfície, tem influência no maior ou menor grau de aglomeração e/ou agregação das partículas, podendo afetar a adsorção e libertação das diferentes espécies. Atendendo às propriedades dos materiais obtidos, concluiu-se que vários HDL estudados são candidatos promissores para aplicação em revestimentos multifuncionais. Para além disso o presente trabalho pode ser usado como suporte na elaboração e validação de modelos computacionais que visam prever a captação e libertação de espécies ativas do HDL.III Quadro Comunitário de ApoioPrograma Doutoral em Ciência e Engenharia de Materiai

The Role of Cu-Based Intermetallic on the Direct Growth of a ZnAl LDH Film on AA2024

The direct ZnAl layered double hydroxide growth on AA2024 is a fast-occurring reaction, yet is characterized by an inhomogeneous film thickness. It has been shown that at the periphery of Cu-rich intermetallic, the flakes tend to be larger and denser. A combination of in situ and ex situ measurements were used to monitor the changes in the layered double hydroxide film grown on the regions of intermetallics. Immediately after immersion, an activation of the intermetallic phases is observed due to the dealloying process with an almost immediate film growth. Dealloying is followed by trenching of the adjacent Al matrix leading to an excessive production of large and dense layered double hydroxide flakes at the periphery of the intermetallic. However, the scanning electron microscopy cross-section images revealed that the trenching process leads to defects in the area surrounding the intermetallic. This could weaken the corrosion resistance performance of the layered double hydroxide conversion coating and lead to adhesion failure of consecutive polymer coatings. Nevertheless, this work highlights a few advantages and drawbacks of the layered double hydroxide conversion coatings and pathways to its potential optimization and improvement

Metabolism of 2,2',3,3',6,6'-hexachlorobiphenyl (PCB 136) atropisomers in tissue slices from phenobarbital or dexamethasone-induced rats is sex-dependent.

1. Chiral polychlorinated biphenyls (PCBs) such as PCB 136 enantioselectively sensitize the ryanodine receptor (RyR). In light of recent evidence that PCBs cause developmental neurotoxicity via RyR-dependent mechanisms, this suggests that enantioselective PCB metabolism may influence the developmental neurotoxicity of chiral PCBs. However, enantioselective disposition of PCBs has not been fully characterized. 2. The effect of sex and cytochrome P450 (P450) enzyme induction on the enantioselective metabolism of PCB 136 was studied using liver tissue slices prepared from naïve control (CTL), phenobarbital (PB; CYP2B inducer) or dexamethasone (DEX; CYP3A inducer) pretreated adult Sprague-Dawley rats. PCB 136 metabolism was also examined in hippocampal slices derived from untreated rat pups. 3. In liver tissue slices, hydroxylated PCB (OH-PCB) profiles depended on sex and inducer pretreatment, and OH-PCB levels followed the rank orders male > female and PB > DEX > CTL. In contrast, the enantiomeric enrichment of PCB 136 and its metabolites was independent of sex and inducer pretreatment. Only small amounts of PCB 136 partitioned into hippocampal tissue slices and no OH-PCB metabolites were detected. 4. Our results suggest that enantioselective metabolism, sex and induction status of P450 enzymes in the liver may modulate the neurotoxic outcomes of developmental exposure to chiral PCBs

PEO Coatings with Active Protection Based on In-Situ Formed LDH-Nanocontainers

In the present work, for the first time Zn-Al layered double hydroxide (LDH) nanocontainers were grown in-situ on the surface and in the pores of plasma electrolytic oxidation (PEO) layer and then loaded with a corrosion inhibitor to provide an active protection. The developed LDH-based conversion process ensures partial sealing of the pores and provides an effective corrosion inhibition on demand leading to increased fault-tolerance and self-healing properties. The structure, morphology and composition of the LDH-sealed PEO coatings on 2024 aluminum alloy were investigated using SEM, TEM/FIB, XRD and GDOES. Electrochemical impedance spectroscopy and scanning vibrating electrode techniques show a remarkable increase in the corrosion resistance and fault tolerance when PEO coating is sealed with a LDH-inhibitor treatment

Biofunctional Coatings Using Direct-Write Fabrication Technique For Surgical Implant Devices

Surface modification of biomaterials is of critical value to attain desired functionality of biomedical devices and implants. Many of the conventional manufacturing methods used for the fabrication of thin film coatings lack the ability to precisely dispense biological compounds without compromising its chemical integrity. This research investigates the use of direct-write inkjet technique for the deposition of multi-layer coatings of biodegradable polymers. The Direct Write inkjet method provides selective deposition and patterning capability for depositing multi-material coatings on biomaterials for a vast array of surgical implant devices (e.g. stents for cardiovascular applications and orthopedic implants)

On the degradation behavior of magnesium, magnesium hydroxide derived coatings and magnesium containing layered double hydroxides with regard to medical applications

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On the early stages of localised atmospheric corrosion of magnesium–aluminium alloys

The surface film on pure magnesium and two aluminium-containing magnesium alloys was characterised after 96\ua0h at 95% RH and 22\ua0\ub0C. The concentration of CO2 was carefully controlled to be either 0 or 400\ua0ppm. The exposed samples were investigated using X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and electron microscopy. The results showed that when the alloys were exposed to the CO2-containing environment, aluminium cations (Al3+) was incorporated into a layered surface film comprising a partially “hydrated” MgO layer followed by Mg(OH)2, and magnesium hydroxy carbonates. The results indicated that aluminium-containing magnesium alloys exhibited considerably less localised corrosion in humid air than pure magnesium. Localised corrosion in the materials under investigation was attributed to film thinning by a dissolution/precipitation mechanism