Synthesis of double mesoporous core-shell silica spheres with tunable core porosity and their drug release and cancer cell apoptosis properties

In this work, we demonstrate a simple two-pot approach to double mesoporous core–shell silica spheres (DMCSSs) with uniform size of 245–790 nm, shell thickness of 41–80 nm and surface area and total pore volume of 141–618 m² g^?1 and 0.14–0.585 cc g^?1, respectively. First, solid silica spherical particles were synthesized by the Stöber method and used as a core. Second, a mesoporous shell could be formed around the silica cores by using an anionic surfactant and a co-structure directing agent. It was found that mesopores can be anchored within dense silica cores during mesoporous silica shell formation, synchronously the base group with surfactant assistant can etch the dense silica cores to re-organize new mesostructure, so that double mesoporous core–shell silica sphere (DMCSS) structure can be obtained by a single surfactant-templating step. The spherical size and porosity of the silica cores of DMCSS together with shell thickness can be tuned by controlling Stöber parameters, including the concentrations of ammonia, solvent and tetraethoxysilane and the reaction time. DMCSS were loaded with ketoprofen and thymoquinone, which are an anti-inflammatory and a potential novel anti-cancer drug, respectively. Both drugs showed controlled release behavior from the pores of DMCSS. Drug uptakes within DMCSS were ～27 and 81 wt.% for ketoprofen and thymoquinone, respectively. Furthermore, DMCSS loaded with thymoquinone was more effective in inducing cancer cell apoptosis than uncontained thymoquinone, because of the slow release of the drug from the mesoporous structure.     

Simultaneous trace-levels determination of Hg(II) and Pb(II) ions in various samples using a modified carbon paste electrode based on multi-walled carbon nanotubes and a new synthesized Schiff base

A modified carbon paste electrode based on multi-walled carbon nanotubes (MWCNTs) and 3-(4-methoxybenzylideneamino)-2-thioxothiazolodin-4-one as a new synthesized Schiff base was constructed for the simultaneous determination of trace amounts of Hg(II) and Pb(II) by square wave anodic stripping voltammetry. The modified electrode showed an excellent selectivity and stability for Hg(II) and Pb(II) determinations and for accelerated electron transfer between the electrode and the analytes. The electrochemical properties and applications of the modified electrode were studied. Operational parameters such as pH, deposition potential and deposition time were optimized for the purpose of determination of traces of metal ions at pH 3.0. Under optimal conditions the limits of detection, based on three times the background noise, were 9.0 × 10⁻⁴ and 6.0 × 10⁻⁴ μmol L⁻¹ for Hg(II) and Pb(II) with a 90 s preconcentration, respectively. In addition, the modified electrode displayed a good reproducibility and selectivity, making it suitable for the simultaneous determination of Hg(II) and Pb(II) in real samples such as sea water, waste water, tobacco, marine and human teeth samples.     

Electrodeposition of Catechol on Glassy Carbon Electrode and Its Electrocatalytic Activity Toward NADH Oxidation

Catechol can be oxidized electrochemically to its corresponding o‐benzoquinone. The electrogenerated quinone can be deposited by cycling the potential at the surface of glassy carbon electrodes. We have studied the electrochemical features of films derived from catechol by cyclic voltammetry. The electrodeposited film shows stable reversible redox response, dependent on pH as anticipated for quinone/catechol functionalities. Glassy carbon electrodes covered with a film derived from catechol exhibit catalytic activity in the electrooxidation of NADH at a low potential. The catalytic current is proportional to the concentration of NADH over the range 0.02–0.34 mM.     

Immobilization of superoxide dismutase onto ordered mesoporous silica nanoparticles and improvement of its stability

In recent years, greater attention has been given to the application of mesoporous materials to the immobilization of enzymes. In this study, the immobilization of superoxide dismutase (SOD) onto the amine-functionalized cubic Ia3d mesoporous silica nanoparticles ([n-PrNH₂-KIT-6]) with an average pore diameter of around 6.5?nm was investigated. This organo-functionalized mesoporous silica was prepared using a non-ionic surfactant and was fully characterized by SEM, XRD, nitrogen adsorption?Cdesorption isotherm and FT-IR spectroscopy. UV?Cvisible spectroscopy studies demonstrated that the immobilized SOD was less prone to thermally induced aggregation than the free moiety. Further investigations using far-circular dichroism measurement intensity indicated that the structure of SOD before and after immobilization onto the [n-PrNH₂-KIT-6] nanoparticles was almost identical and the immobilized enzyme was more stable against GdHCl denaturation relative to the free one.     

Thermodynamic Study of Poly(vinyl pyrrolidone) in Water/Dimethyl Sulfoxide Solutions by Viscometry

In this work, the intrinsic viscosities of poly(vinyl pyrrolidone) with a molar mass of 58?kg?mol^?1 were measured in water?Cdimethyl sulfoxide solutions at temperatures from (298.15 to 318.15)?K. The expansion factors of the polymer chains were calculated from the intrinsic viscosity data. The thermodynamic parameters (entropy of dilution parameter, the heat of dilution parameter, theta temperature, polymer?Csolvent interaction parameter and second osmotic virial coefficient) were derived by the temperature dependence of the polymer chain expansion factor. The thermodynamic parameters indicate that mixtures of water/dimethyl sulfoxide become poorer solvents for poly(vinyl pyrrolidone) as the temperature is increased. Also, the thermodynamic parameters indicate that water/dimethyl sulfoxide mixtures become better solvents for poly(vinyl pyrrolidone) by increasing the volume fractions of dimethyl sulfoxide.     

Nano-sulfated zirconia as an efficient, recyclable and environmentally benign catalyst for one-pot three component synthesis of amidoalkyl naphthols

One pot synthesis of amidoalkyl naphthols by reaction of aromatic aldehydes,2-naphthol and amide/urea using nano-sulfated zirconia as a catalyst is reported.The reaction was carried out under solvent-free conditions.The method gave good yields of amidoalkyl naphthols in short reaction time.The catalyst is recycled for five consecutive times without loss of activity.     

Synthesis and characterization of novel ion-imprinted polymeric nanoparticles for very fast and highly selective recognition of copper(II) ions

This work reports the preparation of new Cu²⁺ ion-imprinted polymeric nanoparticles using 1-hydroxy-4-(prop-2′-enyloxy)-9,10-anthraquinone (AQ) as a vinylated chelating agent. The Cu²⁺ ion found to form a stable 1:1 complex with AQ in methanol solution. The resulting Cu²⁺-AQ complex was copolymerized with ethyleneglycol dimethacrylate, as a cross-linking monomer, via precipitation polymerization method. The imprint copper ion was removed from the polymeric matrix using a 0.1 mol L⁻¹ HNO₃ solution. The Cu²⁺-imprinted polymeric nanoparticles were characterized by IR spectroscopy, scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms. The SEM micrographs showed colloidal nanoparticles of 60-100 nm in diameter and slightly irregular in shape. Optimum pH for maximum sorption was 7.0. Sorption and desorption of Cu²⁺ ion on the IIP nanoparticles were quite fast and achieved completely over entire investigated time periods of 2-30 min. Maximum sorbent capacity and enrichment factor of the prepared IIP for Cu²⁺ were 73.8 μmol g⁻¹ and 56.5, respectively. The relative standard deviation and limit of detection (C_LOD = 3S_b/m) of the method were evaluated as 2.6% and 0.1 ng mL⁻¹, using inductively coupled plasma-atomic emission spectrometry, respectively. It was found that the imprinting technology results in increased affinity of the prepared material toward Cu²⁺ ion over other metal ions with the same charge and close ionic radius. The relative standard deviations for six and twenty replicates with the same nanoparticles were found to be 1.7% and 2.1%, respectively.     

Effect of electrolytes on surface tension and surface adsorption of 1-hexyl-3-methylimidazolium chloride ionic liquid in aqueous solution

Surface and bulk properties of 1-hexyl-3-methylimidazolium chloride [C₆mim][Cl] as an ionic liquid (IL) have been investigated by surface tension and electrical conductivity techniques at various temperatures. Results reveal that the ionic liquid behaves as surfactant-like and aggregates in aqueous solution. Critical aggregation concentration (cac) values obtained by conductivity and surface tension measurements are in good agreement with values found in the literature. A series of important and useful adsorption parameters including cac, surface excess concentration (Γ), and minimum surface area per molecule (A_min) at the air + water interface were estimated from surface tension in the presence and absence of different electrolytes. Obtained data show that the surface tension as well as the cac of [C₆mim][Cl] is reduced by electrolytes. Also, values of surface excess concentration (Γ) show that the IL ions in the presence of electrolyte have much larger affinity to adsorption at the surface and this affinity increased in aqueous electrolyte solution in the order of I^? > Br^? > Cl^? for counter ion of salts that was explained in terms of a larger repulsion of chloride anions from interface to the bromide and iodide anion as well as difference in their excess polarizability.     

Quantification of Sub‐Nanomolar Levels of Aluminum by Adsorptive Stripping Voltammetry Using Rubeanic Acid as a Selective Chelating Agent

A novel, sensitive and selective adsorptive stripping procedure for determination of aluminum is presented. The method is based on the adsorptive accumulation of dithiooxamide (Rubeanic acid) complex of aluminum onto a hanging mercury drop electrode, followed by reduction of adsorbed species by voltammetric scan using differential pulse modulation. The influences of control variables on the sensitivity of the proposed method for the determination of aluminum were studied. The optimum analytical conditions were found to be Rubeanic acid (RA) concentration of 8.0×10^?5 M, ammonia buffer (NH₃? NH₄Cl) pH of 6.5, and accumulation potential at ?50 mV vs. Ag/AgCl with an accumulation time of 60 s. The peak currents are proportional to the concentration of aluminum over the 0.3–70 ng mL^?1 ranges with detection limit of 0.012 ng mL^?1. The procedure was applied to the determination of aluminum in the Lab. Water, HCl of Merck and potato samples with satisfactory results.     

竖板表面温度的变化对磁流体动力学流动的影响

在横向磁场作用下,不可压缩的粘性导电流体,流经一个半无限的竖板,完成了壁面温度变化对磁流体动力学流动的分析.假定由粘性耗散和感应磁场产生的热量可以忽略不计.无量纲的控制方程为二维非稳态耦合的非线性方程.结果显示,磁场参数对空气和水的速度有着抑制作用.