In vitro and in vivo behavior of ketoprofen intercalated into layered double hydroxides

Ketoprofen (Ket) was intercalated into layered double hydroxides (ZnAlLDH and MgAlLDH) using the ionic exchange method. The drug intercalation was confirmed by X-ray diffraction (XRD) and FTIR spectroscopy. Ket release from the inorganic matrix was studied at pH 7.4 in continuous regime with a flow rate of 0.5 and respectively 1.0 ml/min. The kinetical data were interpreted using the Ritger and Peppas model. The data prove that the release kinetics and mechanism depend on the eluent flow rate. Quantification of gastric tolerance shows that the ulcerogenic effect of the intercalated drug is lower than the one of the raw Ket. The antinociceptive effect of both formulations was studied by the hot-plate method performed on mice. The MgAlLDH_Ket formulation shows a tendency towards a stronger antinociceptive effect than its ZnAlLDH_Ket counterpart during the 210 min recorded period.     

Chloride adsorption by calcined layered double hydroxides in hardened Portland cement paste

This study investigated the feasibility of using calcined layered double hydroxides (CLDHs) to prevent chloride-induced deterioration in reinforced concrete. CLDHs not only adsorbed chloride ions in aqueous solution with a memory effect but also had a much higher binding capacity than the original layered double hydroxides (LDHs) in the cement matrix. We investigated this adsorption in hardened cement paste in batch cultures to determine adsorption isotherms. The measured and theoretical binding capacities (153 mg g⁻¹ and 257 mg g⁻¹, respectively) of the CLDHs were comparable to the theoretical capacity of Friedel's salt (2 mol mol⁻¹ or 121 mg g⁻¹), which belongs to the LDH family among cementitious phases. We simulated chloride adsorption by CLDHs through the cement matrix using the Fickian model and compared the simulation result to the X-ray fluorescence (XRF) chlorine map. Based on our results, it is proposed that the adsorption process is governed by the chloride transport through the cement matrix; this process differs from that in an aqueous solution. X-ray diffraction (XRD) analysis showed that the CLDH rebuilds the layered structure in a cementitious environment, thereby demonstrating the feasibility of applying CLDHs to the cement and concrete industries.     

Design of magnetic and fluorescent Mg-Al layered double hydroxides by introducing Fe3O4 nanoparticles and Eu ions for intercalation of glycine

We describe a novel route for the preparation of magnetic and fluorescent magnesium-aluminum layered double hydroxides by introducing Fe₃O₄ nanoparticles and Eu³⁺ ions. From the powder X-ray diffraction results, it was found that the Fe₃O₄ nanoparticles were highly dispersed in the inner void of octahedral lattice, and the Eu³⁺ ions substituted for the Al³⁺ ions and entered into hydrotalcite lattice through isomorphous replacement. Moderate introduction of Fe₃O₄ nanoparticles and Eu³⁺ ions did not change the lamellar structure of magnesium-aluminum layered double hydroxides. Glycine can also be intercalated into this magnetic and fluorescent layered double hydroxides by ion-exchange method. After intercalation of glycine, the basal spacing of magnetic and fluorescent layered double hydroxides increased from 7.6 to 8.8 Å, indicating that glycine was successfully intercalated into the interlayer space of layered double hydroxides. Magnetic measurements reveal that these novel layered double hydroxides possess paramagnetic property at room temperature, and the emission and excitation spectra indicate the layered double hydroxides exhibit fluorescent property.     

The application of layered double hydroxide clay (LDH)-poly(lactide-co-glycolic acid) (PLGA) film composites for the controlled release of antibiotics

Many sites of bacterial infection such as in-dwelling catheters and orthopedic surgical sites require local rather than systemic antibiotic administration. However, currently used controlled release vehicles, such as polymeric films, release water-soluble antibiotics too quickly, whereas nonporous bone cement, used in orthopedics, release very little drug. The purpose of this study was to investigate the use of nanoparticulates composed of layered double hydroxide clays to bind various antibiotics and release them in a controlled manner. Mg-Al (carbonate) layered double hydroxides were synthesized and characterized using established methods. These clay particles were suspended in solutions of the antibiotics tetracycline, doxorubicin (DOX), 5-fluorouracil, vancomycin (VAN), sodium fusidate (SF) and antisense oligonucleotides and binding was determined following centrifugation and quantitation of the unbound fraction by UV/Vis absorbance or HPLC analysis. Drug release from layered double hydroxide clay/drug complexes dispersed in polymeric films was measured by incubation in phosphate-buffered saline (pH 7.4) at 37?°C using absorbance or HPLC analysis. Antimicrobial activity of drug released from film composites was determined using zonal inhibition studies against S. epidermidis. All drugs bound to the clay particles to various degrees. Generally, drugs released with a large burst phase of release (except DOX) with little further drug release after 4?days. Dispersion of drug/clay complexes in poly(lactic-co-glycolic acid) films resulted in a reduced burst phase of release and a slow continuous release for many weeks with effective antimicrobial amounts of VAN and SF released at later time points. Layered double hydroxide clays may be useful for controlled release applications at sites requiring long-term antibiotic exposure as they maintain the drug in a non-degraded state and release effective amounts of drug over long time periods. LDH clay/drug complexes are amenable to homogenous dispersion in polymeric films where implant coating may be optimal or required.     

Structure and magnetic properties of soft organic ZnAl-LDH/polyimide electromagnetic shielding composites

The imidization mechanism, structure, and magnetic properties of organic modified Zinc-aluminum layered double hydroxides/polyimide composites are investigated. During imidization, organic modified Zinc-aluminum layered double hydroxides lose the hydroxyl group and sodium dodecyl sulfate modifier decomposes partly resulting in a loose contact between PI and oxidized Zinc-aluminum layered double hydroxides. The thermal properties of composites are slightly decreased with increasing organic modified Zinc-aluminum layered double hydroxides but the wettability varies oppositely. Comparing to organic modified Zinc-aluminum layered double hydroxides, the saturated magnetization of heated organic modified Zinc-aluminum layered double hydroxides is enhanced slightly due to structural improvement in Fe₃O₄ crystalline domain. Therefore, the magnetic properties are not affected by imidization procedure. The soft magnetic composites have large potential in electromagnetic shielding.     

Study of the preparation,properties and kinetics of anion release in drug intercalated magnetic nanohybrids

We report a new magnetic nanohybrid material to make layered double hydroxides (LDHs) as a targeted drug carrier. The magnetite prepared using a modified conventional coprecipitation technique was embedded in to the fluvastatin intercalated hydrophobic anionic clay through one step process. XRD analysis shows a decrease in lattice parameter of magnetite which is due to generation of stress by the LDHs. Filtered HRTEM image indicates that the magnetic nanohybrid consists of well-defined composite structure and the diameter is around 13 nm. Further, it is shown through magnetisation and ESR study that the exchange interaction between magnetite and drug intercalated LDHs layers shifted the T_B of Fe₃O₄ in magnetic nanohybrid to lower temperatures. In vitro release study of nanohybrid particles at pH 7.4 in PBS and at 37 °C show a faster release for magnetic nanohybrids. The mechanism is probably due to combined effect of interparticle and heterogeneous diffusion via anionic exchange.     

Mg–Al and Zn–Fe layered double hydroxides used for organic species storage and controlled release

Layered double hydroxides (LDH) containing (Mg and Al) or (Zn and Fe) were prepared by coprecipitation at constant pH, using NaOH and urea as precipitation agents. The most pure LDH phase in the Zn/Fe system was obtained with urea and in Mg/Al system when using NaOH. The incorporation of phenyl-alanine (Phe) anions in the interlayer of the LDH was performed by direct coprecipitation, ionic exchange and structure reconstruction of the mixed oxide obtained by the calcination of the coprecipitated product at 400 °C. The reconstruction method and the direct coprecipitation in a medium containing Phe in the initial mixture were less successful in terms of high yields of organic–mineral composite than the ionic exchange method. A spectacular change in sample morphology and yield in exchanged solid was noticed for the Zn₃Fe sample obtained by ionic exchange for 6 h with Phe solution. A delivery test in PBS of pH = 7.4 showed the release of the Phe in several steps up to 25 h indicating different host–guest interactions between the Phe and the LDH matrix. This behavior makes the preparation useful to obtain late delivery drugs, by the incorporation of the anion inside the LDH layer.     

微波场下纳米Mg-Al-LDHs及PO_4~(3-),P_2O_7~(4-)柱撑Mg-Al层状双氢氧化物的合成

用微波加热反应-变速滴加共沉淀法合成了[Mg-Al-CO3]纳米层状双氢氧化物,并以[Mg-Al-CO3]纳米层状双氢氧化物为前体,用微波加热反应-离子交换法制备了PO43-,P2O74-柱撑Mg-Al层状双氢氧化物。该法合成的[Mg-Al-CO3]纳米层状双氢氧化物的粒径约为10-40nm。讨论了微波和变速滴加碱液的速度对纳米层状双氢氧化物的合成的影响。用FT-IR、TEM与XRD对产物进行了表征,结果表明在微波加热反应的条件下可在短时间内用PO43-,P2O74-彻底交换CO32-。     

水滑石作为药物载体--萘普生的插层和缓释

水滑石(LDHs)是由带正电荷类水镁石层和层间的可交换阴离子组成的阴离子型粘土化合物,由于它的生物适应性,能够以它为主体,以药物为客体,插层组装成超分子结构复合物.抗炎药萘普生采用共沉淀法一步插层进入LDHs,用X射线衍射、红外光谱及热分析方法表征了超分子结构,表明层间距离扩大了,即萘普生已经插层组装成功,并且以单层、垂直作用在层间.萘普生柱撑水滑石的药物释放度在模拟肠液(pH7.4的缓冲液)条件下测定,结果表明萘普生柱撑水滑石释放速度降低,具有缓释作用,说明药物--无机混合物材料能够用作有效的药物传输系统.     

Synthesis and characterisation of nanohybrids of olsalazine-intercalated Al–Mg layered double hydroxide

In this study, olsalazine (3,3′-azobis 6-hydroxy benzoic acid) was intercalated into Mg–Al layered double hydroxides (LDHs) by ion exchange or coprecipitation methods to obtain olsalazine–LDH nanohybrids. Powder X-ray diffraction (XRD), Fourier transform infrared spectra and elemental analyses indicate a successful intercalation of olsalazine with a vertical orientation. Intercalation of organic anion of olsalazine into Mg–Al LDH caused the interlayer spacing of LDH to increase from 0.884 to 1.665–1.666?nm as determined by XRD studies. Thermogravimetric analyses propose that the thermal stability of the intercalated organic anion of olsalazine is largely improved compared to the pure form before intercalation due to the host–guest interaction involving the hydrogen bond. Furthermore, in vitro drug release experiments in pH 7.4 phosphate buffer solution have been investigated. The drug molecules during dissolution were exchanged with anions in the medium, thus leading to a slow release, much slower than when the same matrix was used simply mixed with the drug.     

A sustained folic acid release system based on ternary magnesium/zinc/aluminum layered double hydroxides

This study first synthesized and characterized the ternary magnesium/zinc/aluminum layered double hydroxides (Mg/Zn/Al-LDHs) intercalated with folic acid. We prepared the ternary (Mg, Zn, Al) LDH carrier by the introduction of zinc, because magnesium and zinc are both vital minerals of human body. The nanohybrids were prepared by the method of coprecipitation and were characterized by powdered sample X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), UV–vis spectra, and MTT assay. The loading amount of intercalated folic acid was increased to 45.2%, and showed a profile of sustained release with 75% in 250 min. In addition, the folic acid-LDH nanohybrids showed an enhanced thermal stability and a profound buffering property, which demonstrated that the hybrids could protect folic acid against heat degradation and prompt its available diffusion. The cell viability of HEK293T was over 80% after treated with nanohybrids for 72 h. Our results suggested that the ternary folic acid-LDH nanohybrids may function as a useful nutritional tablet to promote the bioavailability of folic acid delivery.     

Sand flower layered double hydroxides synthesized by co-precipitation for CO2 capture: Morphology evolution mechanism,agitation effect and stability

Magnesium–aluminum layered double oxides (Mg–Al-LDO) derived from calcination of layered double hydroxides (LDH) is one of the most capable candidates for CO₂ capture. LDHs with sand flower and dense layered morphology are prepared by co-precipitation method at pH = 10 under different condition with and without stirring. The sand flower LDH prepared with stirring has better CO₂ adsorption performance. Additionally, the sand flower morphology under calcination can be preserved very well, while the morphology can only remain stable below 100 °C after hydrothermal treatment and reconstruction. The formation process of the sand flower LDH is investigated in detail and the related morphology evolution mechanism is proposed. This study can provide insight into the effect of mechanical interaction on chemical reaction and give a new way to control the morphology of layered materials.     

On the release of metronidazole from natural rubber latex membranes

The controlled release of drugs can be efficient if a suitable encapsulation procedure is developed, which requires biocompatible materials to hold and release the drug. In this study, a natural rubber latex (NRL) membrane is used to deliver metronidazole (MET), a powerful antiprotozoal agent. MET was found to be adsorbed on the NRL membrane, with little or no incorporation into the membrane bulk, according to energy dispersive X-ray spectroscopy. X-ray diffraction and FTIR spectroscopy data indicated that MET retained its structural and spectroscopic properties upon encapsulation in the NRL membrane, with no molecular-level interaction that could alter the antibacterial activity of MET. More importantly, the release time of MET in a NRL membrane in vitro was increased from the typical 6–8 h for oral tablets or injections to ca. 100 h. The kinetics of the drug release could be fitted with a double exponential function, with two characteristic times of 3.6 and 29.9 h. This is a demonstration that the induced angiogenesis known to be provided by NRL membranes can be combined with a controlled release of drugs, whose kinetics can be tailored by modifying experimental conditions of membrane fabrication for specific applications.     

BIT-层状双金属氢氧化物纳米杂化物的制备及防霉性能研究

采用共沉淀法将防霉剂1, 2-苯丙异噻唑啉-3-酮(BIT)成功插入到Mg-Al层状双金属氢氧化物层间(LDH), 合成Mg₂Al-BIT LDHs纳米杂化物。采用X射线衍射、傅里叶红外光谱、扫描电子显微镜进行表征。并在pH=4.8和7.2的介质中研究药物缓释动力学。结果显示BIT成功地插入到了LDH的层间, 载药量为44.35%, 释放动力学过程符合准二级动力学方程。将胶囊型防霉剂添加到醇酸树脂涂层中进行霉菌试验。结果表明Mg₂Al-BIT LDHs在耐耗、溶出、析出方面优于BIT, 后期防霉效果更好。     

微波场下纳米Mg-Al-LDHs及PO43-,P2O74-柱撑Mg-Al层状双氢氧化物的合成

用微波加热反应-变速滴加共沉淀法合成了[Mg-Al-CO3]纳米层状双氢氧化物，并以[Mg-Al-CO3]纳米层状双氢氧化物为前体，用微波加热反应一离子交换法制备了PO4^3-，P2O7^4-柱撑Mg-Al层状双氢氧化物．该法合成的[Mg-Al-CO3]纳米层状双氢氧化物的粒径约为10～40nm．讨论了微波和变速滴加碱液的速度对纳米层状双氢氧化物的合成的影响．用FT-IR、TEM与XRD对产物进行了表征，结果表明在微波加热反应的条件下可在短时间内用PO4^3-,P2O7^4-彻底交换CO3^2-。     

Preparation and characterization of melt processed poly(l-lactide)/layered double hydroxide nonocomposites

This work reports the fabrication and physical properties of biodegradable poly(l-lactide) (PLLA) composites containing a fraction of unmodified layered double hydroxides (LDH–NO₃) and γ-polyglutamate-modified layered double hydroxides (γ-LDH) by melt blending process. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) experimental results showed that the original LDH–NO₃ with the certain amount of aggregates was unevenly dispersed throughout the PLLA matrix. Conversely, γ-LDH allows the formation of an intercalated nanocomposite. Although the water vapor permeability of the PLLA/LDH systems was decreased with increasing the loading of LDH, the barrier property of PLLA reinforced with γ-LDH is superior to that of PLLA-L composites. The effects of both LDHs on mechanical and thermal properties of PLLA were also investigated.     

对氨基苯甲酸插层镁铝水滑石的合成、表征及紫外吸收性能

以微波结晶法制备的碳酸根型镁铝水滑石(LDHs)为前体, 对氨基苯甲酸为客体, 由水热法、离子交换法、焙烧复原法三种方法组装合成了对氨基苯甲酸插层镁铝水滑石复合材料。并用XRD、FTIR、TG-DSC、SEM等对其结构进行表征。结果表明: 各种方法均能合成相应的插层水滑石层柱材料, 层间距分别扩大为0.81 nm、0.79 nm、1.45 nm。三种合成材料的紫外吸收强弱与对氨基苯甲酸插层水滑石分子后的层间距大小有关。该研究指出对氨基苯甲酸插层水滑石作为一种紫外吸收层柱材料在化妆品领域具有应用潜力。      

三种方法制备HDPE/LDHs复合材料的性能比较

分别采用硬脂酸表面改性、高密度聚乙烯接枝马来酸酐(HDPE-g-MA)熔融接枝水滑石(LDHs)、乙烯丙烯酸无规共聚物(EAA)熔融接枝水滑石与高密度聚乙烯共混挤出制备纳米复合材料。结果表明,采用EAA接枝水滑石较其他两种方法制备的HDPE/LDHs冲击性能可提高25%以上,拉伸强度可提高35%以上;差示扫描量热(DSC)和X射线衍射(WAXD)等方法证实,EAA熔融接枝LDHs提高了LDHs在HDPE中的分散,有利于HDPE结晶,晶粒细化。采用EAA熔融接枝LDHs填充HDPE可制备性能优异的聚烯烃纳米复合材料。     

Characterization of the chemically deposited hydroxyapatite coating on a titanium substrate

Bioactive hydroxyapatite (HA) coating on titanium (Ti) implant can be used as a drug delivery device. A controlled release of drug around the implant requires the incorporation of drug into the coating material during the coating process. HA coating was prepared using a two-step procedure in conditions suitable for simultaneous incorporation of the protein-based drug into the coating material. Monetite coating was deposited on Ti substrate in acidic condition followed by the transformation of the monetite coating to HA. X-ray diffraction (XRD) confirmed the formation of the monetite phase at the first step of the coating preparation, which was transformed into HA at the second step. Fourier transform infrared spectroscopy demonstrated typical bands of a crystallized carbonated HA with A- and B-type substitution, which was confirmed by the XRD refinement of the structural parameters. Scanning electron microscope was used to observe the morphology of monetite and HA coatings. Adhesion of the coatings was measured using a scratch tester. The critical shearing stress was found to be 84.20 ± 1.27 MPa for the monetite coating, and 44.40 ± 2.39 MPa for the HA coating.     

Effect of layered silicate reinforcement on the structure and mechanical properties of spent polyamide-12 nanocomposites

The aim of this work was to study the structure and mechanical properties of spent polyamide-12 and spent polyamide-12/layered silicate reinforced novel nanocomposites. Layered silicate at 1, 3, 5 and 7 wt.% was incorporated in spent polyamide-12 and its nanocomposites were prepared using single screw injection moulding technique. The interlamellar structure and surface morphology were characterised by transmission electron microscope (TEM) and scanning electron microscope (SEM). Different levels of layered silicate dispersion (as characterised by TEM and SEM) correlated strongly with improvements in mechanical performance. The results showed that the tensile and flexural properties are found to be increased with the incorporation of layered silicate into spent PA-12 matrix. Comparison of tensile and flexural test results between virgin PA-12, spent PA-12 and spent PA-12 nanocomposites showed that spent PA-12 samples have retained 70% of its tensile and 80% of its flexural properties respectively, compared to virgin PA-12.