Layered double hydroxide as novel antibacterial drug delivery system

The cephalosporin class antibacterial agent, cefazolin, was intercalated into layered double hydroxides (LDHs) in order to improve the drug efficiency as well as to achieve the controlled release property. Cefazolin molecules were incorporated into LDH through conventional ion exchange reaction. X-ray diffraction pattern analyses confirmed that cefazolin molecules were intercalated between the interlayer spaces of LDH. Fourier-transform infrared spectra and high performance liquid chromatographs clearly showed that the drug molecules were stabilized in LDH lattice through electrostatic interaction and released without any changes in their chemical integrity. Antibacterial activity of the cefazolin-LDH nanohybrid was also examined by an in vitro test, such as the minimal inhibitory concentration (MIC) by dilution method. Consequently, the cefazolin-LDH nanohybrid revealed an enhanced antibacterial activity compared to the cefazolin itself not only due to an improvement of chemical stability of cefazolin molecules but also due to a controlled release property.     

In vitro release of citrate anions intercalated in magnesium aluminium layered double hydroxides

Layered double hydroxides (LDHs) present a potential application in medicine, as matrices, when intercalated with organic anions of pharmaceutical interest. Once encapsulated, the drug can be released at a rate, depending on the pH of the solution, which may be due to the destruction of the layer by acid attack.The main objective of this work was to evaluate Mg(II)–Al(III)-LDHs for the sustained release of citrate. The citrate intercalated LDHs were prepared by the constant pH coprecipitation technique followed by hydrothermal treatment. Materials were characterized by PXRD, FT-IR, SEM, specific surface area, mean pore diameter analysis, and in vitro release. The release studies were made in a dissolution system that simulates in vivo conditions, obeying the sink conditions. The amount of citrate released, which was determined by HPLC, was 63.8% within 12 h. The total amount released was less than that observed with physical mixture (100%). Thus, these systems seem to be promising for the sustained release of citrate. The data followed the Higuchi square root law (r>0.98) during the release.     

The nonlinear refraction sign turned to reverse by intercalating cresyl violent dye into layered titanate nanosheets

Solid-state dye-doped materials are an attractive alternative to conventional liquid dye solution. In this study, the spectral characteristics of dye cresyl violet before and after intercalating into layered titanate nanosheets and forming a nanohybrid thin film were investigated by measuring absorption and fluorescence spectra. In addition, their nonlinear optical properties were studied using single beam z-scan technique under irradiation of low power continuous wave (CW) produced by DPSS laser with a wavelength of 532 nm. The nonlinear studying results reveal that the dye cresyl violet in solution has a negative nonlinear refractive index, but it reverses to positive after the dye is intercalated into layered titanate nanosheets with a negative nonlinear refractive index forming CV/HTO nanohybrid thin film. This method can provide a way to turn to reverse nonlinear refraction sign of the materials.     

LDH-intercalated d-gluconate: Generation of a new food additive-inorganic nanohybrid compound

Intercalation of d-gluconate into the interlamellae of zinc-aluminum-layered double hydroxide for the formation of a food additive-inorganic layered nanohybrid was accomplished by both direct (co-precipitation) and indirect (ion-exchange) methods. Powder X-ray diffraction (PXRD) together with CHNS and Fourier transform infrared (FTIR) analyses showed that the hybridization of d-gluconate with pure phase and good crystallinity was successfully accomplished by a direct method within ranges of pH 7.5-10, Zn to Al initial molar ratio of 2-5 and DG concentration of 0.05-0.3 M. The same nanohybrid compound was also prepared using an indirect ion-exchange method by contacting the pre-prepared LDH with 0.1 M DG for 80 min. The basal spacing of the nanohybrid synthesized by the direct method ranged between 9 and 12.0 Å while that synthesized by the indirect ion-exchange method was 14.0 Å. The crystallinity of the latter was higher than the former and it inherited the crystallinity of the precursor. This work shows that a food additive, such as d-gluconate, can be hybridized into an inorganic host for the formation of a new nanohybrid compound, which can be used to regulate the release of acidity in the food industry.     

Layered double hydroxide: Inorganic organic conjugate nanocarrier for methotrexate

Layered double hydroxide (LDH)-methotrexate (MTX) nanohybrids were successfully synthesized using ex situ and in situ processes. X-ray diffraction patterns of the synthesized nanopowders revealed that intercalated MTX molecules were stabilized in tilted longitudinal conformation into the hydroxide interlayer space. Two separate hydroxyl peaks were found in the FTIR spectra of LDH-MTX nanopowders suggesting successful intercalation of the MTX molecule into LDH matrix. The synthesized powders were further characterized using transmission electron microscopy (TEM) and selected area electron diffraction (SAED) pattern. HRTEM images showed an increase in interlayer spacing in hydrothermally crystallized LDH-MTX nanohybrids as compared to pristine LDH. The study showed that depending on the synthesis route used to synthesize LDH-MTX nanohybrid, its particle size as well as morphology can be varied at nano scale.     

Controlled release of ketorolac through nanocomposite films of hydrogel and LDH nanoparticles

A novel nanocomposite film for sustained release of anionic ophthalmic drugs through a double-control process has been examined in this study. The film, made as a drug-loaded contact lens, consists principally of a polymer hydrogel of 2-hydroxyethyl methacrylate (HEMA), in whose matrix MgAl-layered double hydroxide (MgAl-LDH) nanoparticles intercalated with the anionic drug are well dispersed. Such nanocomposite films (hydrogel-LDH-drug) contained 0.6–0.8 mg of MgAl-LDH and 0.08–0.09 mg of the ophthalmic drug (ketorolac) in 1.0 g of hydrogel. MgAl-drug-LDH nanoparticles were prepared with the hydrodynamic particle size of 40–200 nm. TEM images show that these nanoparticles are evenly dispersed in the hydrogel matrix. In vitro release tests of hydrogel-LDH-drug in pH 7.4 PBS solution at 32 °C indicate a sustained release profile of the loaded drug for 1 week. The drug release undergoes a rapid initial burst and then a monotonically decreasing rate up to 168 h. The initial burst release is determined by the film thickness and the polymerization conditions, but the following release rate is very similar, with the effective diffusion coefficient being nearly constant (3.0 × 10⁻¹² m²/s). The drug release from the films is mechanistically attributed to anionic exchange and the subsequent diffusion in the hydrogel matrix.     

Sonochemical synthesis and structural characterization of an organic-inorganic nanohybrid based on a copper-dithiocarbamate complex and PMo12O403− polyanion as a novel sonocatalyst

A new organic-inorganic nanohybrid compound, ([Cu{(HOCH₂CH₂)₂NCS₂}₂]₃[PMo₁₂O₄₀] (1)), has been prepared by sonochemical technique using copper(II) dithiocarbamate complex and a Keggin-type polyoxomolybdate in this research. FT-IR, XRD, FE-SEM, TEM, EDX, UV–Vis, TGA, BET, and single crystal XRD analyses were applied to describe the properties of the composition of the nanohybrid. Compound (1) is composed of [PMo₁₂O₄₀]^3– building blocks and [Cu{(HOCH₂CH₂)₂NCS₂}₂]¹⁺ cationic moieties, and electrostatic forces and substantial hydrogen-bonding interactions were applied to pack them; and consequently, a three dimensional supramolecular framework was made based on single-crystal X-ray diffraction patterns. FE-SEM and TEM images approved the morphology of the nanohybrid sample to be extremely penetrable. Very good sonocatalytic performance is shown by this supramolecular nanohybrid in the degradation of Rhodamine B (RhB), which is a cationic organic dye. The results showed complete degradation of cationic RhB (25 mg/L) within 70 min with the rate constant of 0.039min⁻¹ in the presence of nanohybrid (1) and H₂O₂ (4 mmol/L). Also, sonocatalytic activity of the nanohybrid (1) was higher than H₃PMo₁₂O₄₀, showing that the combining Cu(DEDTC)₂ complex with H₃PMo₁₂O₄₀ could be an excellent choice to improve its sonocatalytic activity. The used nanohybrid (1) can be recycled after easily removing from the reaction media by centrifuging, and there was no considerable loss of catalytic activity and retention of the structure.     

Synthesis and characterization of the SnO2-pillared layered titanate nanohybrid

SnO₂-pillared titanate nanohybrid has been prepared by reacting the exfoliated layered titanate sheets with the nanosized SnO₂ sol particles. The stable two-dimensional colloidal nanosheets could be obtained by intercalating tetrabutylammonium cation into the layered protonic titanate, H_xTi_2−x/4□_x/4O₄·H₂O (x=0.67) with a lepidocrocite-like structure, and by successive exfoliation process in an aqueous solution. Monodispersed SnO₂ nano sol particles were prepared by hydrolysis of SnCl₄·5H₂O in the presence of sodium hydroxide, and then the exfoliated titanate suspension was mixed with SnO₂ nano sol solution until the flocculated products formed. The final product was heated at various temperatures in order to complete the grafting reaction of intercalated SnO₂ nano sol on the interlayer surface of layered titanate. Inductive coupled plasma, X-ray diffraction, thermal analysis and N₂-adsorption-desorption isotherms were carried out to study the hybridizing process and the structure of SnO₂-pillared titanate nanohybrid.     

Photopatternable and refractive-index-tunable sol–gel-derived silica–titania nanohybrid materials

Silica–titania nanohybrid materials were synthesized using functionalized organosilanes and organically chelated titanium alkoxide in a simple sol–gel process. The synthesized silica–titania nanohybrid materials exhibited good solution processability and homogeneous dispersion without any phase separation regardless of the ratio of the mixture of the two components. The silica–titania nanohybrid materials exhibited good photoinitiator solubility and effective photocurability with a high degree of degree under ultraviolet (UV) exposure. Because of their high photocurability and solution processability, the silica–titania nanohybrid materials were readily converted into silica–titania nanohybrid films and were used for direct photopatterning without requiring the developing process used in the photomask method. In particular, the refractive indices of the silica–titania nanohybrid materials could be decreased by decreasing the content of chelated titanium alkoxide in the materials. Moreover, the silica–titania nanohybrid films exhibited high transmittance in the visible wavelength range, and their surface roughnesses were very smooth, exhibiting values <1 nm. On the basis of these observations, the fabricated silica–titania nanohybrid materials can be used in solution-processable materials for producing optical and electro-optical elements.     

Ultrasonic synthesis of CeO2@organic dye nanohybrid: Environmentally benign rabid electrochemical sensing platform for carcinogenic pollutant in water samples

A novel organic-inorganic nile-blue - CeO₂ (CeO₂/NB) nanohybrid has been synthesized by environmentally benign ultrasonic irradiation method for the selective determination of the environmental pollutant, carcinogenic hydrazine (HZ) in environmental water samples. Hydrophobic dyes have generally been as redox mediators in electrochemical sensors fabrication due to strong electron transfer capacity and they would allow the oxidation and reduction of the analytes at lower potentials. The CeO₂ nanoparticles were initially synthesized by the ultrasonic irradiation of Ce(NO₃)₂, NH₄OH and ethylene glycol mixture for 6 h using probe sonicator (20 kHz, 100 W) followed by calcination. The organic-dye NB was then added and ultrasonicated further 30 min for the formation of CeO₂/NB nanohybrid material. Various spectroscopic and microscopic tools such as UV–vis and FT-IR spectroscopy, XRD, SEM and high-solution TEM and surface analysis tool Brunauer-Emmett-Teller (BET) confirm the formation of the nanohybrid. HR-TEM images showed the well-covered CeO₂ on NB molecules and the average size of the nanohybrid is ~35 nm. For the fabrication of environmental pollutant electrochemical sensor, the prepared CeO₂/NB nanohybrid was drop-casted on the electrode surface and utilized for the determination of HZ. The nanohybrid modified electrode exhibits higher electrocatalytic activity by showing enhanced oxidation current and less positive potential shift towards HZ oxidation than the bare and individual CeO₂ and NB modified electrodes. The fabricated sensor with excellent reproducibility, repeatability, long-term storage stability and cyclic stability exhibited the sensational sensitivity (484.86 µA mM⁻¹ cm⁻²) and specificity in the presence of 50-fold possible interfering agents with the lowest limit of detection of 57 nM (S/N = 3) against HZ. Utilization of the present sensor in environmental samples with excellent recovery proves it practicability in the determination of HZ in real-time application.     

Antioxidant and anticancer activities of gallic acid loaded sodium alginate microspheres on colon cancer

Polyphenols found in fruits and vegetables are of great interest due to their health benefits. Gallic acid (GA) is an antioxidant with cytotoxic effects. Microspheres are drug carrier systems, where the active substance is trapped in matrix. A controlled release profile is aimed at the target region by preserving the loss of substance and activity. In this study, GA containing microspheres were formed with sodium alginate (NaAlg) in formulations with different ratios. The arrest efficiencies ranged between 11.26 and 72.64%. Release studies were performed at pH 7.4. Optimum conditions were determined as GA/NaAlg ratio 1/8. The microspheres were found to arrest GA and exhibit a controlled release profile. Microspheres were characterized by scanning electron microscope (SEM), differential scanning calorimetry (DSC), X-Ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR) analysis. GA retained its antioxidant activity determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) method and anticancer activity on Caco-2 cells. Further studies are necessary on GA-loaded NaAlg microspheres which have high potential to be used in adjunct and complementary therapies.     

Photophysical properties of fluorescent PMMA/SiO2 nanohybrids for solar energy applications

This work concerning the photophysical properties of fluorescent nanohybrid films based on poly(methylmethacrylate) (PMMA) doped with coumarin dyestuff and entrapped with different concentrations of hydrophilic nanosilica. Spectroscopic tools were applied in order to determine the optimum concentration of nanosilica for the best optical properties for a matrix used as fluorescent solar concentrator. The optical constants and photoluminescence spectra of fluorescent nanohybrid films showed an enhancement of the photon trapping efficiency and matrix stability by increasing the concentration of SiO₂ nanoparticles.     

Gallate-Zn-Al-layered double hydroxide as an intercalated compound with new controlled release formulation of anticarcinogenic agent

A new organic-clay material, in which the organic moiety is intercalated into the inorganic interlayer, was prepared using gallate anion (GA) as a guest, and Zn-Al-layered double hydroxide, as clay host. The ion-exchange technique was found to be effective for the intercalation process in the formation of the compound. Although the basal spacings of the LDH and its intercalated product were fairly similar, FTIR, CHNS and TGA/DTG results indicated that the GA was actually intercalated into the interlayer of the host in parallel orientation. The resulting nanostructure material possessed a well ordered layered structure with 42.2% GA loading (w/w). The release of the anion from the interlayer of the intercalated compound was found to be of controlled manner, governed by the first order kinetic and it was also concentration dependent. The material has potential as a nano-storage of anticarcenogenic agent with controlled delivery capability.     

Encapsulating doxorubicin-intercalated lamellar nanohydroxyapatite into PLGA nanofibers for sustained drug release

In this work, doxorubicin (DOX) was intercalated into layered nanohydroxyapatite (LHAp). The drug loaded LHAp (DOX@LHAp) was then mixed with poly(lactic-co-glycolic acid) (PLGA) and electrospun to yield DOX@LHAp/PLGA composite scaffolds. As control, needle-like nanohydroxyapatite (nHAp) was also used to make an DOX@nHAp/PLGA composite scaffold and bare DOX was used to fabricate DOX/PLGA scaffold. The morphology, release behavior of DOX, and capability to inhibit cancer cells were assessed. The addition of DOX-loaded nHAp to PLGA causes a slight decrease in the average fiber diameter of DOX@LHAp/PLGA as compared to PLGA. The in vitro drug release tests reveal a much faster release of DOX from DOX/PLGA than DOX@LHAp/PLGA. Moreover, DOX@LHAp/PLGA displays a more sustainable release over DOX@nHAp/PLGA due to the storage of DOX in the gallery of LHAp, which is further proved by their cancer cell inhibition results. We believe that the DOX@LHAp/PLGA scaffold has potential as an implantable drug delivery system.     

Optical properties of poly(methyl methacrylate)–titania nanostructure thin films containing ellipsoid-shaped titania nanoparticles from ex-situ sol-gel method at low growth temperature

This paper reports on the linear and nonlinear optical responses of the PMMA-TiO₂ nanohybrid thin films which are synthesized by a flexible ex-situ sol-gel/polymerization process, assisted by spin coating and multi-step baking. Triethanolamine (TEOA) as surfactant and shape controller is used to modify the interface between PMMA and TiO₂, allowing a highly homogeneous dispersion of the ellipsoid-shaped TiO₂ nanoparticles. The resulting nanohybrid thin films have highly optical transparency as proved by the linear absorption photon-energy spectra and indicate an enhanced nonlinear optical (NLO) response as confirmed by the Z-scan technique using 800-nm, 120-femtosecond (fs) laser pulses, highlighting the potential of the nanocomposites for efficient optical devices.     

Ultrasound-alkaline combined extraction improves the release of bound polyphenols from pitahaya (Hylocereus undatus 'Foo-Lon') peel: Composition,antioxidant activities and enzyme inhibitory activity

In this study, ultrasound-assisted alkaline hydrolysis was used to extract polyphenols from pitahaya peel. The effects of sonication time, ultrasonic density, NaOH concentration and the liquid–material ratio on the total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity of the extracts were studied. The composition and content difference of the extracts were analyzed and the inhibitory effect of α-amylase and α-glucosidase was measured. The results of single-factor analysis showed that when the sonication time was 45 min, the ultrasonic density was 32 W/L, the NaOH solution concentration was 6 M and the liquid–material ratio was 30 mL/g, the release of phenolic compounds was the largest and the antioxidant activity was the strongest. An UPLC-QTOF-MS/MS method was used to analyze the components and contents of the extracts. We found that there was a great difference in the component content of the free polyphenol extract and the bound polyphenol extract. From the results, we concluded that there was a strong correlation between the type and content of phenolic compounds and antioxidant activities, indicating that phenolic compounds were the main compounds of these biological activities. Moreover, the bound polyphenol extracts showed a significant inhibitory effect on α-amylase and α-glucosidase was stronger than that of the free polyphenol extracts. In addition, scanning electron microscopy showed that ultrasound-assisted extraction is crucial to the destruction of the cell wall and the release of bound polyphenols. Therefore, the pitahaya peel has the potential for therapeutic, nutritional, and functional food applications, and ultrasound-assisted alkaline hydrolysis is an effective means to release phenolic compounds.     

甲基蓝-钛酸盐纳米聚合物薄膜的光谱和光学非线性研究

 为了满足光学非线性器件设备对工作材料的要求,探究具有高阶非线性效应的固态薄膜材料的制备方法,并对其光学特性进行表征,采用化学插入法,将甲基蓝染料分子插入到具有纳米量级的层状钛酸盐片间,制备了甲基蓝-钛酸盐纳米聚合物薄膜,通过吸收光谱和荧光光谱的测定,发现薄膜的吸收峰相对于染料溶液发生了明显的蓝移,表明染料分子在纳米片间是H-聚集排列。进一步应用单光束连续He-Ne激光Z-扫描技术研究了样品的非线性光学特性,结果显示：插入染料分子的钛酸盐纳米MB/HTO聚合物薄膜具有“负”的非线性折射率,在低功率连续激光作用下聚合物薄膜的非线性折射率系数n2的量级为10-10 m2/W。     

A new strategy to assemble CdSe/ZnS quantum dots with multi-walled carbon nanotubes for potential application in imaging and photosensitization

With objective to enhance luminescence intensities of carbon nanotubes (CNTs), we hereby report the attachment of CdSe/ZnS quantum dots (QDs) on to the surface of shortened Multi Walled Carbon Nanotubes (sMWCNTs). The resultant QDs-sMWCNTs nanohybrid complex have been characterized by Fourier transform infrared (FT-IR) spectroscopy, optical microscopy (OM), ultraviolet (UV) light, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) diffraction spectroscopy and thermogravimetric analysis (TGA). Based on IR peaks characteristics of organic functional groups, optical brightness of sMWCNTs under polarized and UV light, the roughness of the sMWCNTs surface as observed in SEM images and black spots observed on the surface of sMWCNTs in TEM images, it is reasonable to conclude that CdSe/ZnS quantum dots (QDs) were attached on to the surface of sMWCNTs. Additionally, signals of Zn, S, Cd and Se along with carbon on the surface of sMWCNTs in EDX data and onset of thermal degradation of QDs-sMWCNTs nanohybrid complex at much lower temperature than that of sMWCNTs under TGA analysis further confirms the formation of QDs-sMWCNTs nanohybrid complex.     

Evaluation of the antibacterial activity of poly-(<Emphasis Type="SmallCaps">d</Emphasis>,<Emphasis Type="SmallCaps">l</Emphasis>-lactide-co-glycolide) nanoparticles containing violacein

Since violacein—an antibiotic, antiviral, and antiparasitic compound—exhibits poor solubility in water, polymeric poly-(d,l-lactide-co-glycolide) nanoparticles containing this compound improved its solubility and biological activity. The nanoparticles were prepared by the nanoprecipitation method and characterized in terms of average diameter, zeta potential, drug loading, polymer recovery, in vitro release kinetic, and in vitro antibacterial activity. Nanoparticles with diameters between 116 and 139 nm and negative-charged outer surfaces were obtained. Drug-loading efficiency and polymer recovery were 87 and 93%, respectively. In vitro release kinetics assays showed that violacein loaded in these nanoparticles has sustained release behavior until 5 days. Both free and nanoparticles-loaded violacein exhibited in vitro antibacterial activity against Staphylococcus aureus ATCC 29213 and ATCC 25923 strains and exhibiting around two to five times lower minimum inhibitory concentration (MIC) than free violacein, respectively. The encapsulated violacein was efficient against methicilin-resistant Staphylococcus aureus (MRSA) strains. No significant activity against Escherichia coli and Salmonella enterica was found.     

Hydrothermal synthesis of manganese oxide and nitrogen doped graphene (NG-MnO2) nanohybrid for visible light degradation of methyl orange dye

MnO₂ nanoparticles and its nanocomposite with nitrogen-doped graphene (NG) have been fabricated via simple hydrothermal synthesis procedure using water as a solvent. X-ray diffraction (XRD) analysis of the as-prepared samples was used to ascertain the phase purity and crystallite size. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) were employed to study the surface features and particle size of the synthesised samples. The photocatalytic ability of the methyl orange (MO) dye with bare MnO₂ and its hybrid with nitrogen-doped graphene (NG-MnO₂) wer compared with visible light prompted degradation of the dye in absence of these catalysts. The prepared nanohybrid (NG-MnO₂) showed improved photocatalytic efficacy as compared to the pure MnO₂ nanoparticles. The strong ferromagnetic character of nanohybrid helps in easy separation of catalyst even with a bar magnet.