O.N. Srivastava

Targeted killing of Leishmania donovani in vivo and in vitro with amphotericin B attached to functionalized carbon nanotubes

OBJECTIVES This study describes the antileishmanial efficacy of the novel drug formulation of amphotericin B (AmB) attached to functionalized carbon nanotubes (f-CNTs) and compares it with AmB. METHODS f-CNTs were prepared in a two-step chemical carboxylation and amidation process. The AmB was then attached to make f-CNT-AmB and its construction was confirmed by Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The cytotoxicity of the constructed compound, f-CNT-AmB, was assessed in vitro using the J774A.1 macrophage cell line and in vivo using healthy BALB/c mice. Antileishmanial activity of AmB and f-CNT-AmB was assessed in vitro using a macrophage (J774A.1 cell line) model of Leishmania donovani infection. Antileishmanial activity was assessed in vivo by comparing the parasite load of hamsters treated with a 5 day course of AmB, f-CNTs or f-CNT-AmB initiated at 30 days after infection with L. donovani parasites. RESULTS The FTIR spectroscopy and TEM data demonstrate the successful attachment of AmB to f-CNTs. The in vitro cytotoxicity of AmB, f-CNTs and f-CNT-AmB was measured by the cytotoxic concentration required to kill 50% of the cells: 0.48±0.06 μg/mL; 7.31±1.16 μg/mL; 0.66±0.17 μg/mL, respectively, in the J774A.1 cell line. The in vivo toxicity assessment of the compounds in BALB/c mice revealed no hepatic or renal toxicity. Against intracellular amastigotes the in vitro antileishmanial efficacy of f-CNT-AmB was significantly higher than that of AmB (IC50 0.00234±0.00075 μg/mL versus 0.03263±0.00123 μg/mL; P≤0.0001). The percentage inhibition of amastigote replication in hamsters treated with f-CNT-AmB was significantly more than that with AmB (89.85%±2.93% versus 68.97%±1.84%; P=0.0004). CONCLUSIONS The results of these experiments clearly demonstrate that f-CNT-AmB has significantly greater antileishmanial efficacy than AmB and had no significant cytotoxic effects.

On the synthesis of the Mg2Ni alloy by mechanical alloying

The synthesis of the hydrogen-storage alloy Mg2Ni has been carried out through a single-step mechanical alloying employing an energy ball mill. The synthesized ball-milled Mg2Ni alloy has been found to exist in the form of fine (nano) particles with sizes of about 40 A. The nanoparticle form has been found to lead to easy activation for hydrogenation by annealing at 300 °C (about 10−4 Torr vacuum) for 30 min and hydrogen uptake has been found to commence from the first cycle itself.

Effect of Growth Temperature on Bamboo-shaped Carbon-Nitrogen (C-N) Nanotubes Synthesized Using Ferrocene Acetonitrile Precursor

This investigation deals with the effect of growth temperature on the microstructure, nitrogen content, and crystallinity of C–N nanotubes. The X-ray photoelectron spectroscopic (XPS) study reveals that the atomic percentage of nitrogen content in nanotubes decreases with an increase in growth temperature. Transmission electron microscopic investigations indicate that the bamboo compartment distance increases with an increase in growth temperature. The diameter of the nanotubes also increases with increasing growth temperature. Raman modes sharpen while the normalized intensity of the defect mode decreases almost linearly with increasing growth temperature. These changes are attributed to the reduction of defect concentration due to an increase in crystal planar domain sizes in graphite sheets with increasing temperature. Both XPS and Raman spectral observations indicate that the C–N nanotubes grown at lower temperatures possess higher degree of disorder and higher N incorporation.

Antileishmanial activity of nano-amphotericin B deoxycholate

OBJECTIVES The aim of the present study was to compare the efficacy of a nano form of amphotericin B deoxycholate with that of conventional amphotericin B deoxycholate for the treatment of visceral leishmaniasis. METHODS We have formulated nanoparticles (10-20 nM) from amphotericin B deoxycholate (1-2 microM) by applying high-pressure (150 argon) milling homogenization and have tested their efficacy in a J774A cell line and in hamsters. Parasite survival and tissue burden in spleen were evaluated for nano-amphotericin B and conventional amphotericin B. Both nano-amphotericin B and conventional amphotericin B were injected intraperitoneally at 5 mg/kg per day for 5 days. RESULTS The inhibition of amastigotes in the splenic tissue with nano-amphotericin B was significantly more than with conventional amphotericin B (92.18% versus 74.57%, P = 0.005). Similarly, the suppression of parasite replication in the spleen was also found to be significant (99.18% versus 97.17%, P = 0.05). In a cytotoxicity test, nano-amphotericin B against the J774A cell line had a CC(50) of 12.67 mg/L in comparison with 10.61 mg/L for amphotericin B, far higher than the doses used for ED(50). CONCLUSIONS Nanoparticles of amphotericin B had significantly greater efficacy than conventional amphotericin B. This formulation may have a favourable safety profile, and if production costs are low, it may prove to be a feasible alternative to conventional amphotericin B.

Investigations on the synthesis, structural and microstructural characterizations of Mg-based K2PtCl6 type (Mg2FeH6) hydrogen storage material prepared by mechanical alloying

Abstract This paper deals with the formation of new ternary hydride Mg 2 FeH 6 (K 2 PtCl 6 type) in a single-step procedure following the process of mechanical alloying of initial stoichiometric ingredients Mg and Fe under hydrogen. The optimum yield of formation of single phase Mg 2 FeH 6 was achieved by hydrogen (∼10 atm.) milling of constituent elements at a speed of 400 rpm for various milling durations. The structural characterization of the ball-milled (2 Mg+Fe) powder was carried out using Philips X-ray diffractometer by taking samples from the attritor mill at regular intervals of time. It was found that the Mg 2 FeH 6 phase starts forming at a milling duration of 14 h and the optimum Mg 2 FeH 6 phase formation was obtained at 20 h. The proportion of this phase was estimated by employing Rietveld refinement analysis of the X-ray powder diffraction data and it was found to be 63%. This is the highest phase proportion reported so far for the Mg 2 FeH 6 phase when formed from elemental Mg and Fe following the route of mechanical alloying. Together with the Mg 2 FeH 6 phase, some quantity of Fe (about 37%) is also present. Fe, being a magnetic impurity, can be removed leaving the Mg 2 FeH 6 content to be nearly 90–100%. However, such purification was not done in the present investigation. We also investigated synthesis of the material obtained by longer milling durations of 25, 28 and 30 h. The XRD patterns for the 25, 28 and 30 h ball-milled materials revealed that the intensity of Mg 2 FeH 6 peaks is reduced in comparison to the Fe peaks. This implies that beyond 20 h, there is no further increase in the phase proportion and the amorphization starts taking place. The post-sintering process of these mechanically alloyed samples did not improve the Mg 2 FeH 6 phase proportion and yield as evidenced by XRD. The X-ray structural characterizations revealed that the as-milled Mg 2 FeH 6 material (milling duration of 20 h; under H 2 pressure ∼10 atm., speed ∼400 rpm) corresponds to the known face centered cubic structure with lattice parameter a =0.6446(2) nm. The elemental (chemical) compositional analysis was carried out for the mechanically alloyed Mg 2 FeH 6 materials using the EDAX technique. The results confirm the correct stoichiometric ratio of the initial mixture (2Mg+Fe). The surface morphologies of the (2Mg+Fe) mixture before and after mechanical alloying are performed using scanning electron microscopic technique. The SEM explorations reveal the spongy like feature of Mg 2 FeH 6 agglomerates.

Hydrogenation behaviour of the new composite storage material Mg-x% FeTi

Abstract Mg- x wt.% FeTi composite alloys have been successfully synthesized. The hydrogenation behaviour of these alloys has been extensively studied. The materials have been activated at 400 °C under a hydrogen pressure of approximately 30 kg cm −2 and their hydrogen storage capacities and kinetics have been evaluated. The new composite hydrogen storage material in contrast to the native ingredient FeTi, has been found to possess much higher storage capacity and exhibits favourable absorption-desorption kinetics. For Mg-40% FeTi, a storage capacity of ∼3–3.6 wt.% at room temperature (≈27 °C) has been found. This is the highest known capacity exhibited by any hydrogen storage material at ambient conditions. In order to unravel the hydrogenation behaviour of these materials, structural-microstructural characteristics, and chemical composition before and after hydrogenation through X-ray diffraction, scanning electron microscopy and energy-dispersive analysis of X-rays have been carried out. The ambient condition hydrogenation properties of these composite alloys have been found to be strongly correlated with the structural and microstructural characteristics. Based on the observed structural and microstructural characteristics, the details of hydrogenation behaviour have been outlined in terms of cracking of FeTi matrix on hydrogenation and provision of continued fresh surfaces for hydrogenation of FeTi-Mg, Mg-TiMg eutectic mixtures or FeTi-Mg complexes. The present composite alloy corresponds to a new hydrogen storage material with higher storage capacity (≈3–3.6 wt.%) and suitable kinetics (initial hydrogenation in 10 min, saturation hydrogenation in 40 min).

Attachment of biomolecules (protein and DNA) to amino-functionalized carbon nanotubes

An efficient method for the attachment of biomolecules [e.g. bovine serum albumin (BSA) protein and deoxyribonucleic acid (DNA)] to amino-group-functionalized multiwalled carbon nanotubes (f-MWCNTs) was reported. MWCNTs were prepared by spray pyrolysis of a benzene-ferrocene solution in argon atmosphere at ∼850 °C followed by functionalization with an amino group by chemical modification of carboxylic groups introduced on the nanotube surface. This process involves a direct coupling of ethylenediamine with carboxylic groups to introduce amino groups by amide formation. The as-synthesized MWCNTs, f-MWCNTs, and amino f-MWCNTs with BSA protein and DNA were characterized by scanning and transmission electron microscopy, and Fourier transform infrared spectroscopy, which confirm the attachment of biomolecules (BSA protein and DNA) to the amino f-MWCNTs.

Synthesis, band-gap tuning, structural and optical investigations of Mg doped ZnO nanowires

In the present investigation, synthesis, characterizations and the tuning of the optical band gap (Eg) of ZnO nanowires (NWs) has been successfully achieved by introducing Mg as an intentional impurity with varying concentrations Zn1−xMgxO (x = 0, 5, 10 and 20 at. %). Although the ionic radius of Mg2+ (0.57 A) is close to that of Zn2+ (0.60 A) the crystal structure difference and large lattice mismatch between ZnO (wurtzite, 3.25 A) and MgO (rock salt, 4.22 A) causes phase segregation in Zn1−xMgxO with Mg compositions between 37% < x < 62%. Optical measurements of the as grown and Mg doped ZnO NWs shows the optical bandgap tunability from ∼3.35 eV to 3.65 eV as a function of the Mg content. Rietveld refinement of XRD data for the Mg doped ZnO nanowires confirm the wurtzite structure and a continuous compaction of the lattice (in particular, the c-axis parameter) with increasing Mg content. Strong UV with weak visible emission by PL studies establishes the sensitivity of the nanostructures yield, size and band gap to the intentional impurity. This tunability of the band gap of ZnO NWs with an intentional impurity could eventually be useful for optoelectronic applications.

Investigation and optimization of nanostructured TiO2 photoelectrode in regard to hydrogen production through photoelectrochemical process

Abstract This paper reports the investigations on the optimization of nanostructured TiO 2 with respect to optimum photoelectrode area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical output and hydrogen production rate. The nanostructured TiO 2 has been formed by hydrolysis of titanium tetraisopropoxide Ti[OCH(CH 3 ) 2 ] 4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured TiO 2 photoanode of several geometric areas, namely, 0.21, 0.50, 0.72, 1.47 and 1.85 cm 2 , were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to ∼0.5 cm 2 .

Further studies on microstructural characterization and hydrogenation behaviour of graphitic nanofibres

Abstract The present study is aimed at microstructural characterization and hydrogenation behaviour of graphitic nanofibres (GNF) prepared by ethylene gas. The GNF were prepared by thermal cracking of ethylene gas at a temperature of ∼600°C for time durations of 2 h . The structural characterizations have been evaluated by X-ray diffraction and transmission electron microscopy. It was found that the typical length of GNF was in the range of ∼1 to ∼6 μm and most of GNF sample exhibits coil like configuration. The microstructural characteristics as studied by transmission electron microscopy (TEM) techniques after hydrogenation/dehydrogenation were found to consist of curved voids and were significantly different as compared to as grown GNF. The graphitic nanofibres were hydrogenated at 120 atm for 24 h and then dehydrogenated upto 1 atm . The P-C-T curves drawn based on several dehydrogenation runs have revealed the hydrogen storage capacity of present GNF as ∼15 wt % . In addition to hydrogen storage capacity, we have also investigated the desorption kinetics of GNF samples, the hydrogen was desorbed at the rate of ∼57 ml 3 / min .