In vitro drug release characteristic and cytotoxic activity of silibinin-loaded single walled carbon nanotubes functionalized with biocompatible polymers

In this paper, we demonstrate the preparation of silibinin-loaded carbon nanotubes (SWSB) with surface coating agents via non-covalent approach as an effective drug delivery system. The resulting surface-coated SWSB nanocomposites are extensively characterized by Fourier transform infrared (FTIR) and Raman spectroscopies, ultraviolet–visible (UV–Vis) spectrometry and field emission scanning electron microscopy (FESEM). The FTIR and Raman studies show that an additional layer is formed by these coating agents in the prepared nanocomposites during the coating treatment and these results are confirmed by FESEM. Drug loading and release profiles of the coated SWSB nanocomposites in phosphate buffered saline solution at pH 7.4 is evaluated by UV–Vis spectrometry. The in vitro results indicate that the surface-modified nanocomposites, with SB loading of 45 wt%, altered the initial burst and thus, resulted in a more prolonged and sustained release of SB. In addition, these nanocomposites exhibit a pseudo-second-order release kinetic which was driven by the ion exchange between the ionized SWSB and the anions in the release medium. The cytotoxicity effect of the resulting nanocomposites on normal mouse fibroblast cells is evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. It is observed that the surfactant and polymer coating improved the biocompatibility of the SWSB nanocomposites significantly, which deem further exploitation for their application as potential anticancer drug delivery system.     

The seminiferous epithelium cycle and daily spermatic production in the adult maned wolf (Chrysocyon brachyurus, Illiger, 1811)

The duration of the seminiferous epithelium cycle was estimated in adult maned wolves (Chrysocyon brachyurus, Illiger, 1811), by applying intratesticular injections with tritiated thymidine. The total duration of the seminiferous epithelium cycle in this species was calculated in 8.99 days. So, taking into account that approximately 4.5 cycles of the seminiferous epithelium are necessary for the whole spermatogenesis process to complete, the production of spermatozoa from one spermatogonia will take about 40.45 days. The duration of the spermiogenesis was calculated to be 12.3 days. The eight stages of the seminiferous epithelium cycle were described by the tubular morphology method, which is based either on the form and position of the spermatid nuclei and the occurrence of meiotic divisions. The values of the relative frequency for the pre-meiotic, meiotic and post-meiotic phases in this species were 3.5, 0.78 and 4.8 days, respectively. The maned wolf produces about 29 million spermatozoa a day for each testis gram, therefore being classified among the species provided with a high spermatogenetic efficiency.     

Almost periodic solutions for forced perturbed impulsive differential equations

Sufficirnt condition for the existence of almost periodic solutions of forced perturbed systems of impulsive differential equations with impulsive effect at fixed Moments are considered.     

Evaluation of the stability of ethanol in water certified reference material: measurement uncertainty under transport and storage conditions

This study simulated the transport and storage conditions of ethanol in water certified reference material (CRM) produced by the Chemical Metrology Division of Inmetro—DQUIM with the purpose of estimating the measurement uncertainty related to stability. The short-term stability study was performed on five different mass fractions (w) in terms of mg ethanol/g solution of the ethanol in water CRM. The nominal values are w = 0.5, 0.9, 1.1, 3.8 and 4.6 mg/g, at temperatures of 4 and 60 °C. On the other hand, the long-term stability study was developed on four different mass fractions (nominal values): w = 0.5, 0.9, 1.1 and 4.6 mg/g, at a temperature of 20 °C. This paper will show the data from the long-term stability study that took place over 52 weeks. The method used complies with ISO Guide 35, the BCR Guideline for Feasibility Studies and ISO Guide 34. According to the statistical parameters used in both studies, the stability of ethanol in water CRM was confirmed for all of the mass fractions studied.     

Are safe results obtained when the PC-SAFT equation of state is applied to ordinary pure chemicals?

The PC-SAFT equation of state is a very popular and promising model for fluids that employs a complicated pressure-explicit mathematical function (and can therefore not be solved analytically at a specified pressure and temperature, contrary to classical cubic equations). In this work, we demonstrate that in case of pure fluids, the PC-SAFT equation may exhibit up to five different volume roots whereas cubic equations give at the most three volume roots (and yet, only one or two volume roots have real significance). The consequence of this strongly atypical behaviour is the existence of two different fluid–fluid coexistence lines (the vapour-pressure curve and an additional liquid–liquid equilibrium curve) and two critical points for a same pure component, which is obviously physically inconsistent. In addition to n-alkanes, nearly 60 very common pure components (branched alkanes, cycloalkanes, aromatics, esters, gases, and so on) were tested out and without any exception, we can claim that all of them exhibit this undesired behaviour. In addition, such similar phenomena (i.e. existence of more than three volume roots) may also arise with mixtures. From a computational point of view, most of the algorithms used for solving equations of state only search for three roots at the most and are thus likely to be inefficient when an equation of state gives more than three volume roots. To overcome this limitation, a simple procedure allowing to identify all the possible volume roots of an equation of state is proposed.     

Mechanism of oxidation of alanine by chloroaurate(III) complexes in acid medium: Kinetics of the rate processes

The kinetics of the oxidation of alanine by chloroaurate(III) complexes in acetate buffer medium has been investigated. The major oxidation product of alanine has been identified as acetaldehyde by ¹H NMR spectroscopy. Under the experimental conditions, AuCl and AuCl₃(OH)^? are the effective oxidizing species of gold(III). The reaction is first order with respect to Au(III) as well as alanine. The effects of H⁺ and Cl^? on the second‐order rate constant k₂′ have been analyzed, and accordingly the rate law has been deduced: k₂′ = (k₁[H⁺][Cl^?] + k₃K₄K₅)/(K₄K₅ + [H⁺][Cl^?]). Increasing dielectric constant of the medium has an accelerating effect on the reaction rate. Activation parameters associated with the overall reaction have been calculated. A mechanism involving the two effective oxidizing species of gold(III) and zwitterionic species of alanine, consistent with the rate law, has been proposed. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 473–482, 2009     

Determination of the chemical oxygen demand (COD) using a copper electrode: a clean alternative method

A clean alternative method for the determination of chemical oxygen demand (COD) was developed using a copper electrode as an electrocatalytic sensor. The measuring principle is based on oxidation current of organic compounds in the wastewater. The effects of important experimental conditions, such as electrolytic solution concentration and potential scan rate, on analytical performance have been investigated. Analytical linear range of 53.0–2,801.4 mg l⁻¹ COD with detection limit of 20.3 mg l⁻¹ COD was achieved. The procedure was successfully applied to the COD determination in wastewater from soft industries. The results obtained using the proposed method were in good agreement with those obtained using the conventional (i.e., dichromate) COD method. In this fashion, the COD value of a sample can be determined in a simple, rapid, accurate manner, and the end products do not contain toxic metals.     

Corrosion behavior of AA2024-T3 alloy treated with phosphonate-containing TEOS

Protection from corrosion of the aluminum alloy AA2024-T3 coated with a tetraethoxysilicate (TEOS)/aminotrimethyllenephosphonic acid (ATMP) film in a 0.05-mol L⁻¹ NaCl solution was evaluated using electrochemical impedance spectroscopy, scanning electron microscopy, energy disperse spectroscopy, and atomic force microscopy. The present work investigates the influence of different pretreatment procedures of the alloy surface and the ATMP concentration on the corrosion resistance of the coated samples. The undoped sol–gel coatings did not provide adequate corrosion protection. The best corrosion protection was achieved using acetic acid pretreatment and subsequent deposition of an ATMP-modified TEOS film with an optimal concentration of 5.00 × 10⁻⁴ mol L⁻¹ in the deposition bath. The acetic acid pretreatment promotes a decrease in galvanic corrosion and the surface enrichment of aluminum favoring the metalosiloxane and the metal–phosphonic bonds with increasing likely reaction sites, thus promoting the formation of a more homogeneous and compact coating with improved resistance.     

Synthesis of non-glycosidically linked selenoether pseudodisaccharides

Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3-3)Glc, Glc(Se3-6)Glc and Glc(Se3-6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an S_N2 reaction to give selenoethers. Glc(Se3-3)Glc and Glc(Se3-6)Glc were also obtained in deprotected form.