Characterization of colloidal hematite particle shape and dispersion behavior

An elliptically polarized light scattering (EPLS) technique for the size and shape characterization of ellipsoidal hematite particles is presented. The hematite particles are synthesized by aging aqueous FeCl(3) or Fe(NO(3))(3) solutions at 100 degrees C. Different reaction conditions create particles of aspect ratios between 1 (spherical) and 8 (elongated). Cross-sectional diameter and aspect ratio are observed as a function of reaction (aging) time. Growth of the elongated particles, as well as their fractal aggregation behavior, is characterized using EPLS and comparisons are made with photon correlation spectroscopy and TEM measurements.     

Biomimetic pH/redox dual stimuli‐responsive zwitterionic polymer block poly(L‐histidine) micelles for intracellular delivery of doxorubicin into tumor cells

A series of pH/redox dual stimuli‐responsive poly(2‐methacryloyloxyethyl phosphorylcholine)₂₅‐block‐poly(l ‐histidine)_n (p[MPC])₂₅‐b‐p[His]_n, n = 20, 35, 50, and 75) copolymers consisting of a pH‐responsive p(His)_n block and a biocompatible phospholipid analog p(MPC) block connected by a redox‐responsive disulfide linker have been synthesized. The block copolymers are self‐assembled into uniform micelles (～100 nm) in which doxorubicin (Dox) is efficiently encapsulated. The in vitro release profile shows an enhanced release of Dox at low pH (5.0) in 10 mM glutathione (GSH). The in vitro cell viability assays performed using various cell lines show that the blank hybrid micelles have no acute or intrinsic toxicity. A pH‐dependent cytotoxicity is observed with the Dox‐loaded micelles, especially at pH 5.0. Moreover, confocal microscopy images and flow cytometry results show the pH‐dependent cellular uptake of Dox‐loaded micelles. Therefore, the Dox‐loaded micelles can be considered a good candidate for cancer therapy. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2061–2070     

Determination of metabolic profile of anti-malarial trioxane CDRI 99/411 in rat liver microsomes using HPLC

CDRI 99/411 is a potent 1,2,4‐trioxane anti‐malarial candidate compound of the Central Drug Research Institute, India. This study aimed to conduct comprehensive in vitro metabolic investigations of CDRI 99/411 to corroborate its preclinical investigations. Preliminary in vitro metabolic investigations were performed to assess the metabolic stability [in vitro half‐life (t_1/2) and in vitro hepatic intrinsic clearance (Cl_int)] of CDRI 99/411 in male Sprague–Dawley rat and human liver microsomes using validated high‐performance liquid chromatography with photodiode array detector. The observed in vitro t_1/2 of the compound in rat and human liver microsomes was 13 min with in vitro Cl_int 130.7 ± 25.0 μL/min/mg and 19 min with in vitro Cl_int 89.3 ± 17.40 μL/min/mg. These observations suggested moderate metabolic degradation and in vitro Cl_int with insignificant difference (p > 0.05) in the metabolic stability profile in rat and human. Hence, in vitro metabolic investigations were performed with rat liver microsomes. It was observed that CDRI 99/411 exhibited sigmoidal kinetics. At nonlinear regression (r ≥ 0.99) EC₅₀ and Hill slope values were 17 µm and 1.50, respectively. The metabolism of CDRI 99/411 was primarily mediated by CYP3A2 and was inferred by CYP reaction phenotyping with known potent inhibitors. Two metabolites of CDRI 99/411 were detected which were undetectable on incubation with 1‐aminobenzotriazole and ketoconazole. Copyright © 2011 John Wiley & Sons, Ltd.     

Aggregation behavior of single-walled carbon nanotubes in dilute aqueous suspension

The aggregation behavior of colloidal single-walled carbon nanotubes (SWNT) in dilute aqueous suspensions was investigated using a novel light scattering measurement technique. The aggregation of SWNT in three suspensions was examined: (1) nanotubes after acid treatment; (2) as-received nanotubes stabilized by a nonionic surfactant; and (3) acid-treated nanotubes with nonionic surfactant. Continuous light scattering measurements of the SWNT suspensions (probing the 38-436 nm length scale) made over two weeks showed that the nanotubes in each sample formed networks with fractal-like structures. The as-received nanotubes were stable over the measurement period, while the acid-treated nanotube suspension showed greater dispersion variability over time, yielding looser structures at large length scales and more compact structures at smaller length scales. The addition of surfactant to the acid-treated suspension significantly enhanced nanotube dispersion.     

Mössbauer study of braunite

Braunite mineral from Triodi manganese deposits (India) has been studied by Mössbauer spectroscopy. Room temperature Mössbauer spectra show a well resolved quadrupole splitting which is attributed to the substitution of iron in Mn (2) site. Emergence of another doublet at liquid nitrogen temperature has been attributed to the location of small quantities of iron in Mn (4) site. Iron is in Fe III and high spin state. At 4.2 K the internal magnetic field is 415 kOe.     

Determination of 3-hydroxy pterocarpan, a novel osteogenic compound in rat plasma by liquid chromatography-tandem mass spectrometry: application to pharmacokinetics study

A rapid, sensitive and selective LC‐MS/MS method for the quantitative analysis of 3‐hydroxy pterocarpan (S006‐1709) in female rat plasma has been developed and validated. A Discovery RP₁₈ column was used for the chromatographic elution using acetonitrile and 0.1% acetic acid in water as mobile phase (80:20 v/v) at the flow rate of 0.5 mL/min. MS/MS analysis was performed using a triple quadrupole mass spectrometer with electrospray ionization in negative ion mode using biochanin as an internal standard (IS). Extraction of S006‐1709 and IS from rat plasma was done by liquid–liquid extraction method using diethyl ether. The LC‐MS/MS method was sensitive with 1.95 ng/mL as the limit of detection and 3.9 ng/mL as the lower limit of quantification. The method was linear in the concentration range of 3.9–1000 ng/mL. The percentage bias for intraday and interday accuracy was not greater than 4.2 and the %RSD for intraday and interday precision was not greater than 13.2. The recoveries of S006‐1709 and IS were 73.9–79.3 and 85.7%, respectively. S006‐1709 was found to be stable in various stability studies. The validated LC‐MS/MS method was successfully applied for the oral pharmacokinetics study of S006‐1709 at 10 mg/kg in female Sprague–Dawley rats. Copyright © 2010 John Wiley & Sons, Ltd.     

Assessment of Factors Influencing the Agrobacterium-mediated in planta Seed Transformation of Brinjal (Solanum melongena L.)

An efficient and reproducible in planta transformation method was developed for brinjal using seed as an explant. The brinjal seeds were infected with Agrobacterium tumefaciens EHA 105 harbouring pCAMBIA 1301-bar plasmid, and the transformants were selected against BASTA®. Several parameters influencing the in planta seed transformation such as pre-culture duration, acetosyringone concentration, surfactants, duration of sonication, vacuum pressure and vacuum duration have been evaluated. The putatively transformed (T ₀) brinjal plants were screened by GUS histochemical analysis. Among the different combinations and concentrations tested, when the 18-h pre-cultured brinjal seeds were sonicated for 20 min and vacuum infiltered for 3 min at 500 mm of Hg in Agrobacterium suspension containing 100 μM acetosyringone, 0.2 % Silwett L-77 favoured the Agrobacterium infection and showed maximum transformation efficiency. Among the five brinjal varieties evaluated, Arka Samhitha showed maximum transformation efficiency at 45.66 %. The transgene was successfully transmitted to progeny plants (T ₁) which was evidenced by GUS histochemical analysis, polymerase chain reaction and Southern hybridisation. The in planta protocol developed in the present study would be beneficial to transfer the economically and nutritionally important genes into different varieties of brinjal, and the transgenic brinjal plants can be produced in less time (approximately 27 days).     

Size and Shape Prediction of Colloidal Metal Oxide MgBaFeO Particles from Light Scattering Measurements

The size and structure of colloidal metal oxide (MgBaFeO) particles are determined using an Elliptically Polarized Light Scattering (EPLS) technique. The approach is based on a hybrid experimental/theoretical study where the experimental data are compared against predictions obtained using a T-Matrix model that accounts for particle shape irregularities. A power-law distribution function with two parameters is employed to account for the particle size distribution. The refractive index of the particles in ethyl alcohol is calculated based on the Maxwell-Garnet formula. The experiments are conducted using a second-generation nephelometer. It is shown that the current EPLS measurements can effectively be used for identification of both the shape and the size of the colloids.     

Identification of the Dispersion Behavior of Surface Treated Nanoscale Powders

The stability of highly acidic metal oxide surface treatments on rutile titanium dioxide nanopowders (40 nm nominal particle size) is examined. Dispersions are characterized in terms of their sedimentation behavior and light scattering pattern. Using elliptically polarized light scattering (EPLS), agglomerates are identified as fractal structures and size analysis is performed according to the measured fractal dimension. The effect of ultrasonication on agglomerate size and structure (compactness) is quantified for tungsten oxide and molybdenum oxide surface treatments, as well as untreated titanium oxide. Surface treatments are shown to increase dispersion stability, as witnessed by the decreased size of large agglomerates and sedimentation behavior. The EPLS fractal studies, combined with ultrasonication analysis, reveals information of agglomerate shapes, primary particle bonds and structures, and agglomerate growth mechanisms.