Kalpana Awasthi

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.

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.

Ball-milled carbon and hydrogen storage

Abstract We report the formation of carbon in different nanoparticle forms obtained by ball-milling of graphitic carbon. Ball-milling of graphite was carried out in Szegvari attritor at room temperature for varied times i.e. 24, 48 and 100 h in hexane medium. The characterization of ball-milled graphitic carbon (BMC) samples was done by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. The self-coagulated carbon agglomerates were obtained for the case of 24 and 100 h BMC samples. The formation of coiled nanotubes and nanofibres was observed in the BMC sample. The BMC samples with and without nickel (Ni) catalyst were subjected to hydrogenation cycling in a Sieverts type apparatus fabricated in our laboratory. It has been found that BMC sample can adsorb hydrogen. The hydrogen adsorption capacity has been found to be ∼0.6 wt % .

Synthesis and characterization of carbon nanotube?polyethylene oxide composites

We have investigated the structural, electrical and mechanical properties of multi-walled carbon nanotube (MWNT)?polyethylene oxide (PEO) composites. Composites with different wt% (between 0 and 50?wt% of MWNTs) were prepared and characterized by the scanning electron microscopic technique. Enhanced electrical conductivity and mechanical strength were observed for the MWNT?PEO composites. The conductivity measurements on the MWNT?PEO composite films with highest concentration of MWNTs (~50?wt%) showed an increase of eight orders (~7.5 ? 10?8 to 6.52?S?cm?1) of magnitude in conductivity from bare PEO film. The temperature dependence of the conductivity for MWNT (~50?wt%)?PEO composite showed predominantly semiconducting behaviour. The elastic modulus and tensile strength of an MWNT (~50?wt%)?PEO film were increased by about five-?and tenfold respectively, as compared to the corresponding values for a PEO film.

Large scale synthesis of bundles of aligned carbon nanotubes using a natural precursor: turpentine oil

Bundles of aligned carbon nanotubes (ACNTs) have been synthesised by spray pyrolysis of turpentine oil (inexpensive precursor) and ferrocene mixture at 800°C. Turpentine oil (C10H16), a plant-based precursor was used as a source of carbon and argon as a carrier gas. The bundles of ACNTs have been grown directly inside the quartz tube. The as-grown ACNTs have been characterised through X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopic techniques. Scanning electron microscope images reveal that the bundles of ACNTs are densely packed and are of ∼70–130 µm in length. High-resolution transmission electron microscopy and Raman spectroscopy observations indicate that as-grown multi-walled carbon nanotubes (CNTs) are well graphitised. These CNTs have been found to have outer diameters between ∼15 and 40 nm. This technique suggests a low-cost route for the large-scale formation of ACNTs bundles.

EFFECT OF NITROGEN VARIATION ON THE SYNTHESIS OF VERTICALLY ALIGNED BAMBOO-SHAPED C–N NANOTUBES USING SUNFLOWER OIL

To examine the role of NH3 on bundles of aligned bamboo-shaped carbon–nitrogen (C–N) nanotube were synthesized the pyrolysis of ferrocene (Fe(C5H5)2) and sunflower oil mixtures with NH3 being the source of nitrogen. The concentration of NH3 was varying in volume (vol). Optimized temperature and concentration of ferrocene were 825°C and 10 mg/ml, respectively. With the increase of nitrogen concentration the bundles are breaking in nearly equal parts. With nitrogen doping, the nanotubes have a bamboo-like structure and reveal degraded crystallinity of graphitic sheets. Nitrogen plays key role in generating equal compartments inside the carbon nanotube. The nanotubes were characterized by scanning electron microscopy and transmission electron microscopy that reveal the vertically aligned and hollow structural features of the nanotubes. FTIR shows the incorporation of N atom inside carbon framework and Raman spectrum indicates the enhancement of the defects inside C–N nanotube due to the N atom in C–N nanotube.

PREPARATION OF CARBON–NITROGEN NANOTUBES (CNNTs)–POLY ETHYLENE OXIDE (PEO) COMPOSITES FILMS AND THEIR ELECTRICAL CONDUCTIVITY MEASUREMENT

The present work describes the preparation characterization and electrical conductivity measurement of carbon–nitrogen (C–N) nanotubes–PEO composites films. CNNTs–PEO composite films have been prepared by using the solution cast technique and characterized by scanning electron microscope (SEM PHILIPS XL-20). The DC electrical conductivity measurements of the composite films revealed that for PEO film conductivity has been found to be ~ 7.5 × 10-8 Scm-1, and for C–N nanotubes (~ 20 wt.%)–PEO film it was found to be ~6.2 Scm-1 at room temperature. Thus, compared to the PEO film, the conductivity of the C–N nanotubes (~ 20 wt.%)–PEO composite film is eight orders of magnitude higher. The same conductivity of ~ 6.2 Scm-1 for the carbon nanotubes (CNT)–PEO composites comes out at 50 wt.% of CNT in PEO as reported earlier by our group. The conductivity increases with the increase of temperature, confirming the semiconducting nature of the C–N nanotubes–PEO composites.

SYNTHESIS OF CARBON NANOTUBES THROUGH CARBON ARC EVAPORATION EMPLOYING Mm, La, AND Ce CATALYSTS

We report the formation of carbon nanotubes (CNTs) in, high density when mischmetal Mm (a natural mixture of several rare earth elements) is used as catalyst. Mm has been found to work as a better catalyst than either lanthanum (La) or cerium (Ce). The formation of composite nanorods when the catalyst La is used in very high concentration (∼90wt.%) has also been described and discussed.